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103
6
Developing Restoration Strategies for Temperate
Forests Using Natural Regeneration Processes
Holger Fischer, Franka Huth, Ulrike Hagemann, and Sven Wagner
CONTENTS
6.1 Introduction ........................................................................................................................ 104
6.1.1 Forest Restoration as a Holistic Challenge ......................................................... 104
6.1.2 Tree Regeneration as a Driver in Forest Restoration ........................................105
6.2 The Natural Regeneration Process .................................................................................. 107
6.2.1 Flowering, Pollination and Fruiting as Prerequisites .......................................108
6.2.1.1 Flowering .................................................................................................108
6.2.1.2 Pollination ................................................................................................ 109
6.2.1.3 Fruiting ..................................................................................................... 110
6.2.2 Mechanisms of Seed Dispersal and Consequences for Regeneration ........... 111
6.2.2.1 Zoochory .................................................................................................. 112
6.2.2.2 Anemochory ............................................................................................ 113
6.2.2.3 Dispersal Distances ................................................................................ 113
6.2.3 Costs, Benets, and Implications of Seed Storage ............................................. 114
6.2.3.1 Orthodox and Recalcitrant Seeds ......................................................... 115
6.2.3.2 Seed Banks ............................................................................................... 115
6.2.3.3 Widespread Susceptibility ..................................................................... 116
6.2.3.4 Predation by Rodents ............................................................................. 116
6.2.3.5 Predation by other Vertebrates .............................................................. 116
6.2.3.6 Scatter Hoarding ..................................................................................... 117
6.2.3.7 Pathogens ................................................................................................. 117
6.2.4 Germination in Stressful Surroundings: A Narrow Bottleneck ..................... 117
6.2.4.1 Germination and Safe Site ..................................................................... 117
6.2.4.2 Light .......................................................................................................... 118
6.2.4.3 Litter and Soil Organic Matter .............................................................. 118
6.2.4.4 Interaction with Mycorrhizae ................................................................120
6.2.4.5 Physical Damage to Seedlings ..............................................................120
6.2.5 Seedling Survival and Establishment: The Fine Step to Maturity ................. 120
6.3 Overstory Restoration Strategies Oriented toward the Natural
DisturbanceRegime .......................................................................................................... 121
6.3.1 Emulating Overstory Conditions Originating from Large-Scale
Disturbances to Support Ecological Processes .................................................. 121
6.3.2 Manifold Harvesting as a Strategy for Managing Structural and Species
Diversity .................................................................................................................. 123
6.3.2.1 Clearcut System ....................................................................................... 124
6.3.2.2 Seed Tree System ..................................................................................... 125
104 Restoration of Boreal and Temperate Forests
6.1 Introduction
6.1.1 Forest Restoration as a Holistic Challenge
Forest restoration projects have become increasingly common around the world and many
studies have accumulated in this eld during the last decades. Forest restoration means
changing the forest landscape component toward a “more natural” situation (sensu Fischer
and Fischer 2012). But what is “natural”? Bradshaw (2002) called it the “original ecosystem”
and focused on two major attributes: ecosystem structure and ecosystem function, with
typical values for both attributes that are reduced by ecosystem “degradation.” Ecological
restoration is an activity that also ideally results in the return of an ecosystem to an undis-
turbed status (Palmer and Filoso 2009). On the path back to the original ecosystem state,
natural recovery as well as ecological restoration offer many developmental options. As
these denitions necessitate a holistic approach, the attention in recent restoration projects
has turned to the integration of ecosystem services. Similarly, restoration actions focused
on enhancing biodiversity should also support increased provision of ecosystem services
6.3.2.3 Retention Tree System ............................................................................125
6.3.2.4 Irregular Shelterwood ............................................................................ 126
6.3.2.5 Emulating Old-Growth Gap Conditions for Regeneration
Processes ..................................................................................................126
6.4 Restoration Strategies for the Active Manipulation of Below-Canopy Stand
Components ........................................................................................................................ 129
6.4.1 Emulating Large-Scale Disturbances to Support Ecological Below-
Canopy Processes .................................................................................................. 130
6.4.2 The Function of Ground Vegetation: Facilitation versus Competition .......... 132
6.4.2.1 The Role of Ground Vegetation in Natural Forests ............................133
6.4.2.2 Interactions between the Different Hierarchical Strata
ofForestEcosystems ............................................................................... 134
6.4.2.3 Using Ground Vegetation to Promote or Discriminate
AgainstSpecic Tree Regeneration ...................................................... 135
6.4.3 Direct Control of Species Composition by Establishing Articial
Regeneration ........................................................................................................... 136
6.4.4 Manipulating the Small-Scale Seedling Environment ..................................... 137
6.4.5 Utilizing Deadwood to Improve Regeneration Survival ................................. 138
6.4.5.1 How Deadwood Facilitates Regeneration ...........................................139
6.4.5.2 Seed Interception, Retention and Storage............................................ 139
6.4.5.3 Germination and Seedling Establishment .......................................... 139
6.4.5.4 Seedling and Sapling Survival .............................................................. 140
6.4.5.5 Protection from Browsing Damage ...................................................... 140
6.4.6 Effects of Deadwood Properties .......................................................................... 140
6.4.6.1 Abundance ............................................................................................... 140
6.4.6.2 Origin and Type ...................................................................................... 141
6.4.6.3 Size ............................................................................................................ 141
6.4.6.4 Decay Status ............................................................................................. 141
6.4.7 Deadwood and Forest Restoration ...................................................................... 141
References .....................................................................................................................................142
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105Developing Restoration Strategies for Temperate Forests
(Rey Benayas etal. 2009). This approach presents an opportunity for enhancing benets
to human livelihood and funding sources as well as generating public support for such
initiatives (Trabucchi etal. 2012).
Restoration ecology is “repairing” degraded, damaged, or destroyed ecosystems usually
adversely affected by human activity. Restoration activities are often aimed at increas-
ing the land-base of a particular ecosystem; its biodiversity, resilience, and resistance, the
provision of ecosystem services and ecosystem sustainability (see Aronson and Alexander
2013). The formulation of sustainability as an integral part of restoration practice is essen-
tial at the very least with respect to the status quo of many European forest areas, which
have a long history of human intervention. Historic human impacts in these forests range
from the elimination of predators, clearing for agricultural use and settlements, the intro-
duction of domestic grazing stock, management for timber production, and management-
induced change of tree species with the introduction of nonnative, partly invasive species,
which disturb the natural cycle of forest regeneration (Willoughby and Jinks 2009).
Restoration success in general, and regeneration success in particular, are controlled by
these historical occurrences and past silvicultural practices within a forest stand, includ-
ing past and present species composition, stand structure, wildlife, and potential man-
agement-related soil disturbance. Further, recent anthropogenic modications such as
atmospheric deposition (e.g., of nitrogen) or climate change (Fischer and Wagner 2009)
also modify forest regeneration in time and space.
6.1.2 Tree Regeneration as a Driver in Forest Restoration
Tree regeneration is the most relevant and effective initial step in the context of forest
restoration, as every silvicultural action at this stage affects the development at least of
the next stand generation, and potentially beyond. From an ecological perspective, discus-
sions about the forest life cycle focus on the processes involved in replacing mature trees
with the next tree generation as well as the colonization of new habitats. Out of all forest
developmental phases, the regeneration phase offers the best opportunity to manipulate
tree species and forest structure, making it a key for achieving restoration objectives. In
this regard, Löf etal. (2012) dened the practice of planting trees and shrubs as a key com-
ponent of forest restoration.
The majority of existing studies on forest regeneration emphasize reforestation follow-
ing timber harvest for industrial purposes (Oliet and Jacobs 2012). Even today, there are
land use practices, such as surface mining (Hüttl and Bradshaw 2001) or remediation of
forest soils (Kauppi etal. 2012), that create extremely harsh site conditions for restoration.
These sites require amelioration using direct sowing and planting (Josa etal. 2012), often
in combination with intensive mechanical site preparation. These activities are all active
management interventions (Holl and Aide 2011). However, in almost every area with arti-
cial regeneration, the natural invasion of trees, shrubs, and other autotrophs (Mueller-
Dombois and Ellenberg 1974) may also play a role. In forest restoration, some groups
advocate relying exclusively on natural regeneration and succession dynamics rather than
active regeneration and restoration activities (Hüning etal. 2008; Baasch etal. 2009).
The different regeneration methods, each feature advantages and disadvantages.
Although forest restoration and natural succession both lead to ecosystem change, they
are quite different with respect to the degree of intentionality and should therefore be
clearly differentiated. While forest restoration is the assisted, intentional, guided recon-
struction of forests, natural succession is regarded as unintended, neither prescribed nor
directed by humans (Ciccarese etal. 2012). Despite public perception, natural regeneration
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106 Restoration of Boreal and Temperate Forests
techniques are not innately superior or always more appropriate than articial techniques
for restoring forest ecosystems. Where management objectives require precise timing and
a particular tree species composition of the restored forest, active intervention at the regen-
eration stage is essential. Interventions should be based on management objectives, the
evaluation and interpretation of site conditions, and profound silvicultural knowledge and
skills. Appropriate regeneration choices must contribute to current management objec-
tives and be exible enough for retaining future options. As forests are typically long-lived
ecosystems, forest managers continuously face the risk that changing conditions in the
future will negate the assumptions on which they based their current decisions.
In traditional forest management, regeneration success is dened by a minimum stock-
ing density of genetically adapted, vigorous young trees of a dened species composi-
tion with adequate leader shoot growth and high competitive power (McWilliams etal.
1995, Ponder 1997, Wagner etal. 2010) and appropriate root development (Brunner etal.
2009; Bayer etal. 2013). These criteria also apply to regeneration for restoration purposes.
Although stocking levels may differ depending on management objectives, the nancial
return to the landowner is in many cases an important objective of forest restoration,
together with other objectives such as biodiversity conservation. Restoration often aims to
alter species composition, sometimes formulating additional requirements for a minimum
number of individuals of certain species, and stocking levels can thus deviate from values
required for maximum timber production or quality. Restoration objectives may also call
for changes in stand structure. When the target is an uneven-aged stand structure, den-
ing an appropriate stocking density is somewhat more complex, because the relationship
between seedling density at a given time and the recruitment of trees for the upper tree
layers is not necessarily straightforward (Lundqvist 1995).
The complex task of choosing regeneration measures can be approached in two steps,
analysis and decision. At several scales—from stand to microhabitat—environmental con-
ditions must be evaluated for different regeneration measures to properly predict options
and obstacles over the entire regeneration phase (Nyland 1996). This has to be done for
each stage of the life cycle in order to identify potential environmental hazards as well as
environmental prerequisites. Recommended regeneration measures can then be derived
from these options (Perala and Alm 1990; Jobidon 1994; Van Der Meer etal. 1999).
Analysis can be a daunting task, and practical considerations often necessitate compro-
mises and decision-making based on incomplete information. For example, site conditions
may be surveyed and analyzed at different scales and levels of intensity (Barnes etal. 1998;
Kimmins 1987; Gholz and Boring 1991; Smith etal. 2007). In practice, the quality and inten-
sity of site surveys depends on the available resources and may be constrained by factors
such as staff availability (both numbers of individuals and their competence) as well as the
willingness of the forest owner to invest in site mapping and analyses. However, the forest
manager’s knowledge and experience regarding local site conditions and the performance
of indicator species may offset the lack of complete information. Such experience may thus
be critical in accounting for changes that may occur after the regeneration intervention,
such as potential competing vegetation (Wagner etal. 2010). Once the objectives regarding
the future provenance, species composition, stand and age structure have been set, the
forest manager must decide on the appropriate regeneration method or combination of
methods, adapted management intensity, and adequate timing of all interventions.
Forest restoration is in some ways a new application of silvicultural expertise and a chal-
lenge for any silviculturist. Therefore, we must remain mindful that widely used regen-
eration techniques may be underlain by different objectives and assumptions. We may
carefully use existing knowledge, but should also be prepared to seek new information
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107Developing Restoration Strategies for Temperate Forests
or analyses. After all, it is a substantial challenge for forest research to create new and rel-
evant knowledge for forests with a high dynamic potential both in time and space.
The following sections give an overview of the inherent and external limitations of the
regeneration process, structured by stage, and the measures available to counteract them.
Our aim in this chapter is to point out the relevance of single life cycle stages within the
regeneration process in the context of restoration ecology, in particular by illustrating the
interactions between these stages, site factors, and the techniques available to intervene in
the regeneration process. We therefore restrict the scope of the chapter to ecological aspects.
6.2 The Natural Regeneration Process
The events associated with the regeneration process of different tree species are some
of the most striking phenomena within forests. The natural regeneration cycle includes
numerous relevant stages, starting with the owering of mature trees and ending with the
No
damages
Storage
No vector
Missing
Failing
Damages
Limited
resources
Seedling
development
Favorable
environmental
conditions
Rich
Mast
Fruiting
Flowering and
pollination
Effective
vectors
Artificial regeneration
:
planting
Successful
establishment
and growth of
juveniles
Dispersal
Natural regeneration
Unfavorable
environmental
conditions
Germination
Artificial regeneration
:
sowing
Safe sites
No safe sites
Resource-rich
FIGURE 6.1
The regeneration cycle as a cascade of ecological processes and their success and failure in interaction with
environmental conditions exemplarily for European beech.
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108 Restoration of Boreal and Temperate Forests
recruitment and establishment of juvenile trees. Figure 6.1 shows a cascade of these eco-
logical processes interacting with environmental conditions and their success and failure,
illustrated with European beech (Fagus sylvatica). Both in theory and practice, forest ecolo-
gists have debated for decades over the predominant limiting factors responsible for insuf-
cient natural regeneration within individual forest stands. A vast literature illustrates
the complex interactions between mature trees, environmental conditions, and seedling
response; but the majority of publications focus only on a few particular phases with high
relevance for regeneration success. Ammer etal. (2011), however, underline the need to
look at the regeneration cycle in its entirety and to disentangle the multiple factors that are
involved throughout the entire process.
Understanding the regeneration cycle is crucial for achieving sustainable forest manage-
ment and ensuring “acceptable” forest restoration. From a silvicultural point of view, an
acceptable result for each stage can be dened by a minimum density of seeds, seedlings,
or saplings required for regenerating a given site; and the limitations are by denition
factors causing lower densities than required. In this context, a biological phenomenon
will be called “effective” if adequate densities result. This is particularly important in seed
dispersal. A detailed analysis of every individual stage will make it easier to evaluate the
absence of acceptable natural regeneration density in a specic area, particularly because
the failure of any single stage within the complex generative cycle will compromise the
overall regeneration success.
6.2.1 Flowering, Pollination and Fruiting as Prerequisites
Reproductive phenology, starting with oral initiation, via full orescence through pol-
lination and seed or fruit maturity, is well known for temperate conifers, but less studied
for temperate hardwoods (Owens 1995). In order to manipulate the regeneration cycle for
specic restoration aims, the drawbacks and opportunities for natural regeneration should
be fully understood, because constraints to seed or fruit reproduction are manifold and
inuence all subsequent stages of the regeneration cycle.
6.2.1.1 Flowering
The majority of seasonally owering trees ower infrequently. The generative character is
caused by a range of developmental, physiological, and environmental conditions such as
species-specic pubescence, light intensity, minimum and maximum temperature, water
regime, and nutrients. Before the generative character of buds and subsequent owering
becomes visible, particular biochemical changes are measurable (e.g., gibberellins mediate
and promote growth and development within the owering processes of conifers; Bonnet-
Masimbert 1987). Many temperate forest trees exhibit so-called “indirect owering,” char-
acterized by a period of dormancy between oral initiation and pollination (Owens 1995).
In most cases, oral initiation occurs before the onset of winter dormancy. In some spe-
cies, the percentage of reproductive buds can be predicted from their external morphology
(Owens and Blake 1985).
In silvicultural management, it is a common practice to modify light conditions in order
to increase the production of reproductive buds and improve owering. Such methods
have been successfully applied in North American temperate conifers (Ross and Pharis
1985) and European beech stands (Holmsgaard and Olsen 1966), where special thinning
regimes, adequate tree spacing, and crown management are promising strategies when nat-
ural regeneration is missing. Although higher temperatures at the time of oral initiation
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109Developing Restoration Strategies for Temperate Forests
may enhance owering in temperate trees (Ross 1989; Owens 1995), in contrast low winter
temperatures enhance owering in some species such as Eucalyptus nitens (Moncur and
Hasan 1994). Water stress and associated aspects such as shallow soils, poorly drained
soils such as pseudogleys, soil compaction, and anoxia have also been said to enhance
owering in temperate hardwoods and conifers (see Owens 1995 and references therein).
Often successful owering and later stages are not differentiated because the frequency
of (sometimes inconspicuous) owering may be less obvious than the frequency of seed or
fruit production at the end of the reproductive cycle. This is not permissible, however, and
may lead to false conclusions and misinterpretations when evaluating natural regenera-
tion success.
6.2.1.2 Pollination
Successful pollination is the next step within the regeneration cycle (Figure 6.1). It tends to
be relatively constant from year to year. Although the majority of tree species in temperate
forests are wind-pollinated, a few species have other pollination strategies, for example,
relying on insects (Prunus avium, Robinia pseudoacacia, and Tilia spec.) or even water (Abies
spec., see Chandler and Owens 2004). Ashley (2010) demonstrated that pollination and
pollen dispersal are complex phenomena which are inuenced by many ecological pro-
cesses. She cited numerous parentage studies showing long-distance dispersal of pollen
to be common in both wind- and animal-pollinated tree species, with average pollination
distances being hundreds of meters.
Generally, forest trees are highly diverse organisms genetically, and pollen dispersal is
usually considered the main driver of genetic relatedness patterns (Sagnard etal. 2011).
Genetic variability depends on population size and the spatial distribution of tree indi-
viduals. For tree species characterized by a large and continuous range such as European
beech, the genetic diversity within populations is typically high while the genetic diversity
between populations is comparatively low (Thomsen and Kjær 2002; Buiteveld etal. 2007;
Jump and Penuelas 2007; Nyari 2010). Species with small population size in glacial refu-
gia and a low mixing rate between postglacial recolonization lineages typically feature a
strong genetic differentiation among but not within populations (e.g., Fraxinus excelsior;
see Rüdinger etal. 2008; Dobrowolska etal. 2011). However, even within populations or
forest stands, genetic diversity is rarely homogeneously distributed, with genetic similar-
ity between individuals often decreasing with increasing distance between them, such as
described for the genera Fagus (Jump and Penuelas 2007) and Quercus (Bacilieri etal. 1994).
The knowledge of spatial genetic patterns resulting from population history and limited
gene ow can be important for regeneration management, in order not to misrepresent
genetic diversity of species or populations in the progeny population and to avoid autog-
amy (self-fertilization, measured by the heterozygosity of the resulting juvenile genera-
tion) when distances between parental trees are high (Streiff etal. 1998). Due to the impact
of lethal regressive genes, germination percent, height growth, or resilience can be lower
in the case of self-pollination compared to cross-pollination (Hattemer 2005). Hence, pol-
len transfer is especially important for small populations whose habitat has been consider-
ably reduced (e.g., Silver r (Abies alba), see Wolf 2003) or fragmented (e.g., genus Ulmus, see
Goodall-Copestake etal. 2005).
The degree of gene transmission from the parent to the juvenile generation in forest stands
depends on the applied silvicultural harvesting and regeneration methods (Finkeldey and
Ziehe 2004; Hosius etal. 2006). For example, the removal of a few mature trees from a stand
prior to seed production in uneven-aged Plenterwald forests may have no measurable impact
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110 Restoration of Boreal and Temperate Forests
on the genetic structure and variability of the naturally regenerated understory (Lefèvre
2004). Similarly, other regeneration strategies such as “Femelschlag” have no negative effects
on the progeny generation—the longer the regeneration period, the more uneven-aged the
progeny population. In this method, tree cutt ing intensity is low and explicitly heterogeneous
with respect to horizontal structure; the next generation consists of different age classes.
This method of harvesting and regeneration is believed to be well-suited to accommodate
the variable mast years of different forest tree species (Geburek and Turok 2005). In contrast
to these silvicultural regeneration systems, shelterwood and seed tree retention systems are
expected to affect genetic diversity to a higher degree, because only a limited number of
trees are left for reproduction or are given a limited number of years to pollinate (Buchert
1992). This is especially important if the trees left in the stand are genetically inferior.
6.2.1.3 Fruiting
Although effective pollination tends to be relatively constant from year to year, many tree
species uctuate between years of high and low reproduction, with few “average” years.
Even when owering occurs, fruiting can be erratic. Studies have shown that in harsh
climates, single extreme weather events can invalidate supposedly promising background
conditions for mast years. Mast years have been variously dened as years where seed
production exceeds the long-term mean by some predetermined level (LaMontagne and
Boutin 2009 and references therein). Mast seeding is a phenomenon referring to individual
trees producing seeds synchronously at “superannual intervals” (Rapp etal. 2013), which
leads to large uctuations in seed production at the population level. Evolutionary ecolo-
gists hypothesize that mast seeding occurs because synchronous reproduction among
conspecics is associated with several tness benets, including enhanced rates of pol-
lination (Kelly and Sork 2002), increased attraction of seed dispersers (Li and Zhang 2007),
and reduced seed predation (Curran and Leigthon 2000; Crone etal. 2011).
Apart from single weather events, the intensity and frequency of fruiting depends on
the age and vitality of the individual tree, as well as on the presence or absence of pollina-
tors, or seed and ower predators. Light-demanding pioneer species such as birch (Betula
spp.), aspen (Populus tremula), rowan (Sorbus aucuparia), and willow (Salix spp.) naturally
ower and fruit with high abundance after reaching (early) pubescence. While abundant
birch seed crops are observed at 2–3 year intervals in Northern Europe (Hynynen etal.
2010), Central European birch (Betula pendula) produces seeds almost annually (Cameron
1996), although with varying quantities (Huth 2009).
Heavy-seeded species such as beech, oak, or chestnut (Juglans regia), feature pronounced
mast years that usually occur at intervals longer than 5 years (Watt 1923; Sork 1993; Röhrig etal.
2006). Recent observations, particularly from beech forests in Europe (Hilton and Packham
2003), indicate a positive trend in mast frequency: according to the general opinion among
foresters in Northern and Central Europe, it has been easier to regenerate common tree spe-
cies during the last 20 years than previously. An analysis by Övergaard etal. (2007) illustrates
the observed trend of generally increasing mast year frequency, associated with increases in
mast crops. They found in Sweden that the average interval between mast years of beech has
decreased from 4 to 6 years for the period ~1700–1960, to 2.5 years during the most recent
30years, and there were two consecutive mast years twice during the latter period.
Climatic changes, especially increasing temperatures, may be responsible for the higher
frequency of mast years, but increased atmospheric nitrogen deposition may also be a con-
tributing factor (Schmidt 2006). More frequent mast years will likely simplify planning of
forest regeneration measures (Övergaard etal. 2007), but it is a legitimate question whether
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111Developing Restoration Strategies for Temperate Forests
and how this phenomenon is interlinked with tree and stand vitality and thus with sus-
tainable stand development.
Fruiting of species often varies from one year to the next and is not synchronized bet ween
species, even though seed rain may be synchronized among cooccurring species of the
same genus (Shibata and Nakashizuka 1995). Alternating abundance and composition of
seed rain (Lässig etal. 1995) may favor certain species on disturbed sites. In forest stands
with advance regeneration or dense ground vegetation, for example, a heavy-seeded spe-
cies will be favored over a light-seeded species by sudden disturbances such as wind-
throw (natural), harvesting, and site preparation (anthropogenic), because heavy seeds are
not impeded by vegetation and their seedlings can thus occupy local regeneration niches
rst. As seeds are dispersed over limited distances, seed availability highly depends on
the distance and on the strength of the nearest seed source (Clark etal. 1998). Selective
removal of seed trees of undesired species prior to site preparation or other regeneration
measures can thus be used to promote regeneration of desirable species. For dioecious tree
species, removal cutting can be restricted to female individuals.
Once a tree reaches maturity, its contribution to seed production depends on its canopy
position, vigor, and genetics. Preparatory cuttings, which are commonly used to precondi-
tion overstory trees in shelterwood systems (e.g., for beech), and fertilization aimed to induce
owering and fruiting can improve the generative potential of individual trees. The seed
crop per area can be maximized by an optimal combination of individual tree vitality and
tree density (Nyland 1996). Due to poorly developed individual tree crowns, this optimum
is seldom present in stands of maximum density. Selective thinning aimed at the promotion
of trees with good phenotypes has therefore been suggested as a possibility for improving
the probability of transferring desirable characteristics to the new stand generation (Nyland
1996). However, losses in genetic variability in stands that were thinned accordingly are
barely detected over the course of a single stand generation (Müller-Stark etal. 2005).
6.2.2 Mechanisms of Seed Dispersal and Consequences for Regeneration
The number of seed dispersal studies has grown exponentially during the last two decades
(Bullock and Nathan 2008; Schupp etal. 2010). Indeed, dispersal models are indispensable
for ecological research, because seed dispersal links the adult reproductive cycle to the
seedling stage (Wang and Smith 2002; Rother etal. 2013) and strongly inuences the demo-
graphic process of plants (Harper 1977).
Forester managers need to know how many seeds trees can produce and how far these
seeds are typically dispersed, for example, when initiating natural regeneration by har-
vesting single trees. For many forest stands, these seemingly simple questions are rela-
tively difcult to answer, because it is challenging to quantify the number of seeds prior
to dispersal, and postdispersal dynamics may have an important effect on recruitment
and later fertility (Wenny 2000; Birkedal etal. 2009). Although fertility can be inferred
from postdispersal seed densities (Schurr etal. 2008), this requires knowledge about the
parental tree from which the seeds originate, which is difcult to obtain because the seed
rain of neighboring trees typically overlap. The study of such environmental effects seems
particularly important for understanding and predicting plant performance in heteroge-
neous environments and their response to environmental change.
With the help of “inverse modeling” (Ribbens etal. 1994; Clark etal. 1998), tree fertility
and seed or fruit dispersal originating from a single individual are estimated simultane-
ously. Inverse modeling takes advantage of the specic probability that—out of a larger
number of trees—a particular tree can be considered the source of seeds caught in single
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112 Restoration of Boreal and Temperate Forests
traps placed in dened positions within a forest stand (Stoyan and Wagner 2001). However,
this method cannot be simply used to estimate effects of spatially varying environments
on fertility and dispersal. The process of seed dispersal can be structured into three com-
ponents (modied from Millerón etal. (2013):
1. Primary dispersal, which is the movement of seeds and fruits from the tree to
the ground by gravity (barochory). Apart from the potential area of plant recruit-
ment, this term also subsumes interlinked processes relevant for spatial patterns
of adult plants such as germination, predation, and competition (Nathan and
Muller-Landau 2000).
2. Secondary dispersal, which is dened as the removal of seeds and fruits by more
or less effective vectors such as animals (zoochory), wind (anemochorie), water
(hydrochory), and topographical gradients, once the seed is on the ground (Forget
etal. 2005).
3. Effective dispersal, which is the combination of primary and secondary dispersal
plus establishment.
In plant populations, recruitment necessitates component 1 (or 2) and 3. For trees in the
temperate zone, gravity, wind, and animals (especially via birds and mammals) are the
most important dispersal vectors. The term “dispersal range” refers to the distance a seed
can move from an existing population or a single adult tree. Seed density on the ground
generally decreases monotonically with distance from a seed source (Clark etal. 1999),
resulting in very low densities at long distances (Bullock and Clarke 2000). Effective dis-
persal distances are seldom greater than a few times the height of the seed bearer (Nyland
1996), but differences among species are considerable (Ribbens etal. 1994).
6.2.2.1 Zoochory
For some species, invasion into stands of other species can be regularly observed, for
example, oak or beech invading pine stands via zoochory of specialized birds (Pons and
Pausas 2008; Sheffer etal. 2013). In this context, far-ying jays (Garrulus glandarius) are
particularly important (Bossema 1979). They are abundant in oak and pine stands of all
densities and clearly prefer acorns to beechnuts, whereas nuthatches (Sitta europaea) are
more abundant in beech stands and prefer beechnuts to acorns (Perea etal. 2011). There are
other birds such as great tits (Parus major) that remove acorns and beechnuts, especially in
stands dominated by oaks, but they do not store the seeds.
It has been shown that zoochorous seed removal is determined by the structure of the
dominant vegetation because some habitats are more suitable for the disperser animals.
Pure pine stands can be appropriate regeneration sites as early as in the pole stage, when
light availability on the ground steadily increases (Sonohat etal. 2006). Densities of more
than 2000 oak stems ha−1 of acceptable quality can thus develop if deer browsing does not
stunt or kill oaks smaller than 1.3 m (Mosandl and Kleinert 1998; Schirmer et al. 1999;
Stimm and Knoke 2004). Fencing can further accelerate this process.
The European jay has regenerated several thousand ha of pine stands with oak in Lower
Saxony, Germany (Otto 1996). Some foresters deliberately offer acorns to jays in special
boxes to facilitate the establishment of oak. Similar observations of succession have been
made for rowan, well known in Central and Eastern Europe for its ability to invade pure
Norway spruce stands via dispersal by birds (Zywiec etal. 2013) or mammals (Guitián and
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113Developing Restoration Strategies for Temperate Forests
Munilla 2010). Carnivorous mammals such as the red fox (Vulpes vulpes) and the European
pine marten (Martes martes) are also the main mammalian frugivore-seed dispersers in
temperate Scots pine forests (González-Varo etal. 2013) for rowan. In contrast to Scots
pine, however, gaps of a minimum size are essential for rowan to succeed in spruce stands.
These ndings provide a key starting point for understanding and modeling tree succes-
sion in restoration processes that include mammal-mediated seed dispersal, such as con-
nectivity, home range expansion, and recolonization.
In addition to mammals, another effective zoochorous vector in secondary dispersal
and predation can be seed removal by rodents. While some rodents feed on acorns thus
leading to seed predation, others (mainly scatter-hoarders) can also act as effective dis-
persers (e.g., for sessile and common oak, see den Ouden etal. 2005; for ash (Fraxinus excel-
sior) and wych elm (Ulmus glabra): Hulme and Hunt 1999). The role of rodents in tree and
shrub seed removal varies depending on the species, but is affected mainly by seed size
and morphology (Jansen etal. 2004) as well as by seed encounter and exploitation (Hulme
and Hunt 1999). However, successive dispersal movement and distance to rodent shelter
(shrub cover) are more important factors than acorn weight to determine dispersal dis-
tance and acorn survival (Perea etal. 2011). The ecological balance between seed predation
and effective dispersal is still largely unknown.
Effective dispersal not only depends on the quantity of dispersed seeds but also on the
quality of the seed dispersal process. According to Schupp etal. (2010), “quantity” is the
number of visits of a dispersal agent multiplied by the number of seeds dispersed per visit,
while “quality” is the probability that a dispersed seed survives handling by the disper-
sal agent in a viable condition (quality of treatment in the mouth and gut) multiplied by
the probability that a viable dispersed seed will survive, germinate, and produce a new
adult (quality of deposition). These interactions are well analyzed by Gómez etal. (2003)
for holm-oak (Quercus ilex) and one of its main dispersers, the European jay in a heteroge-
neous Mediterranean landscape. Moreover, there are animals not only effective for disper-
sal but also germination (Paulsen and Högstedt 2002).
6.2.2.2 Anemochory
Although seed removal by birds has been demonstrated to play an important role in long-
distance dispersal in the context of forest restoration, wind is certainly of special relevance
as a widely available seed dispersal vector that can transport many seeds over long dis-
tances. Unlike water, wind can transport seeds in all directions and is therefore important
for dispersal to upstream wetlands (Soons 2006) and to areas not directly connected to a for-
est. Compared to animals, wind transports seeds to a wider range of sites, therefore reaching
more sites but with lower seed densities. In wind dispersal, the effective dispersal distance
is determined by wind speed and direction, which can be inuenced by the density and
height of the remaining trees (Greene and Johnson 1996; Karlsson 2001). Many pioneer tree
species with seeds of very low sinking velocity rely on wind as a seed dispersal vector. Apart
from open landscapes, wind-dispersed birch species are thus also able to regenerate in pure
conifer stands, particularly favored by heavy disturbances (Perala and Alm 1990) that create
large gaps favorable for the growth of pioneer tree species (Huth and Wagner 2006).
6.2.2.3 Dispersal Distances
Forest ecologists commonly differentiate between mean dispersal distance (MDD), long
dispersal distance (LDD), and sometimes maximal dispersal density (MAXDD), because
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114 Restoration of Boreal and Temperate Forests
these distance measures have different functional relevance in ecosystem development
and the spatial management of forests. While the MDD is relevant in conventional silvi-
culture to produce quality timber by means of high stand density, the MAXDD is impor-
tant for long-term dispersal and invasion scenarios, particularly in fragmented landscapes
(Malanson and Armstrong 1996) and for natural species recolonization (Pacala etal. 1996).
For example, habitat clustering is a frequent phenomenon within forest restoration, result-
ing from habitat loss and/or fragmentation processes. Both processes operate at different
resolution and with different intensity, for example, wind-throw, forest clearcutting, site
degradation, or the segregation of tree species in pure stands due to management. The
recurrence of trees at different spatial scales varies according to landscape structure and
species dispersal strategies. Disentangling the relative impact of habitat loss and fragmen-
tation on the long-term survival of certain species requires understanding of the interac-
tions of habitat cluster availability and dispersal distance, and how they affect dispersal
success. Cattarino etal. (2013) addressed this problem by quantifying the magnitude of
these interactions, and emphasized the relevance of long distance dispersal.
The relevance of LDD and MAXDD with respect to restoration is stressed in another
example: An understanding of dispersal processes is relevant in the context of preventing
and controlling invasive alien tree species or managing the distribution of such species. To
predict the seed dispersal potential of Fraxinus pennsylvanica, an invasive alien in Germany,
Schmiedel etal. (2013) used a stochastic model predicting the number of seeds for a single
tree individual. The results were used to calculate species-specic dispersal distances and
the effect of wind direction for different assumptions regarding dispersal directionality
(isotropic and anisotropic). The topic of invasive species clearly illustrates the need to dif-
ferentiate between MDD and LDD, because the latter is of paramount importance for inva-
sion dynamics and the rate of colonization; further exemplied by Pairon etal. (2006) for
black cherry, a highly invasive forest tree species in Europe.
Knowledge of dispersal distances is required to determine “effective” seed density,
which should not focus on the maximum observed distances. In mixed stands, the effec-
tive distance to seed trees of all species is of particular interest if aiming to maintain the
current species mixture. If effective dispersal is lacking or the rate of recolonization is too
slow, for example, at long distances from seed sources, silvicultural techniques such as
direct sowing or planting of later successional species with limited dispersal ability can be
used to facilitate the establishment of desired tree species.
6.2.3 Costs, Benefits, and Implications of Seed Storage
Spatial discordance between primary and effective seed dispersal in forest stands indicates
that postdispersal processes are responsible for differences between seed rain densities
and seedling recruitment patterns. Although seed rain is observed mostly below and near
canopy trees, saplings are often established far from parental trees (e.g., for Fagus sylvatica:
Milleron etal. 2013, for maple (Acer spp.): Wada and Ribbens 1997). This discordance pat-
tern may be the result of secondary dispersal by animals or density-dependent effects
such as the Janzen-Connell effect (Janzen 1970 and Connell 1971). The period between
dispersal and recruitment, the so-called storage phase, is characterized by high potential
mortality rates and is thus one of the most relevant phases of the regeneration cycle.
For some tree species, seeds are not stored but germinate within the current growing
season (e.g., Acer rubrum, and Ulmus laevis). But for most temperate and boreal tree species,
seeds are stored on or within the forest oor because of unfavorable conditions for germi-
nation and growth outside the vegetation period. Winter storage is thus an adaptation of
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115Developing Restoration Strategies for Temperate Forests
species to the annual climatic cycle at middle and high latitudes (Runkle 1989). Extended
periods of opportunistic dormancy (i.e., enforced and induced dormancy; see Harper 1977)
can be regarded as an alternative to dispersal in space, sometimes referred to as dispersal
in time (Willson 1993).
6.2.3.1 Orthodox and Recalcitrant Seeds
Seeds of many tree species are sensitive to desiccation, humidity, anoxic conditions, frost,
fungal decay, or predation, and are therefore difcult to store. Seed storage patterns and
conditions not only vary among species, but also within species and even provenances. The
response of seeds to storage conditions and duration is generally expressed by the terms
“orthodox” (desiccation-tolerant) and “recalcitrant” (desiccation-sensitive; see Roberts
1973). Orthodox seeds can be stored in situ for years, and also articially under cool low-
moisture conditions. Many forest tree species of important genera belong to this group,
including all European coniferous trees. Sugars (e.g., sucrose and rafnose) play an impor-
tant role as storage substances, accumulated in cells during maturation and degraded
during the rst 10–20 h of germination (Downie and Bewley 2000). In seed banks, seeds
of species with dormancy adaptations (e.g., Robinia pseudoacacia, Prunus serotina) can sur-
vive dormancy periods of several years. In contrast, the seeds of oak (Quercus spp.), beech
(Fagus sylvatica), or chestnut (Castanea sativa) are recalcitrant; they are intolerant of desicca-
tion and cannot be stored in the soil for more than one winter without the loss of viability
(Doody and O’Reilly 2008).
6.2.3.2 Seed Banks
Seed densities can increase rapidly following a major seed production event (e.g., masting
in heavy-seeded oak and beech) or progressively by a combination of consecutive smaller
dispersal events and seed storage (dormancy), thus building up seedling (ash, maple,
and black cherry, Prunus serotina) or sapling banks (beech and r) under closed canopies
(Szwagrzyk etal. 2001). Most of these species produce fewer seeds per tree and lower seed
densities on the ground over time than more light-demanding species (Ribbens etal. 1994;
Clark etal. 1998). Most tree species in temperate forest ecosystems do not build up long-
term soil seed banks or sapling banks (Halpern etal. 1999; Bossuyt and Honnay 2008).
But existing seedling and sapling banks are strategies by which low seed production is
compensated for by prolonged storage time. Underlying mechanisms include architec-
tural adaptations such as the relative proportion of leaf and branch biomass (Kohyama
1987), high morphological plasticity such as opportunistic plagiotropy in beech (Brown
1951), and metabolic adaptations such as low respiration rates (Walters and Reich 2000).
Individual seedlings are often capable of vigorous responses to sudden improvements in
resource supply, and may thus occupy promising niches in advance of other less tolerant
species.
Seed banks often serve as reservoirs of tree species diversity, which buffer the com-
position of plant populations and inuence the postdisturbance dynamics of vegetation
succession (Royo and Ristau 2012). Aerial seed banks, where seeds are retained in tree
crowns, have been observed for some re-adapted species outside Europe such as Pinus
contorta (Richardson 1998). For forest restoration strategies, forest managers can use a
range of regeneration methods relying on seed banks, but they must be familiar with the
particular mechanisms needed to break the dormancy of the desired tree species. These
mechanisms can be activated by light or heat (i.e., radiation), leading to particular cutting
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116 Restoration of Boreal and Temperate Forests
regimes or prescribed burning, as, for example, applied in eucalypts or serotinous pine
and spruce species (Smith etal. 2007).
6.2.3.3 Widespread Susceptibility
Upon making ground contact (primary dispersal), seeds are exposed to new risks and
mortality factors, among them are pathogens and predation. Postdispersal seed loss can
cause an important bottleneck in the natural regeneration of many tree species. The rela-
tive importance of each mortality factor varies depending on seed quantity and microhab-
itat conditions, resulting in spatial discordance in the performance of each regeneration
stage. In order to minimize postdispersal loss, some tree species produce seeds in irregu-
lar mast years. The intermittent mass production of seeds, for example, in beech stands,
is often invoked as a strategy evolved by some plant taxa to overcome the capacity of seed
predators to consume all seed (predator satiation; see Kelly and Sork 2002).
6.2.3.4 Predation by Rodents
Seed loss due to mice is common (Madsen 1995) and partly determined by storage dura-
tion. The ability of a rodent population to affect seed reserves at the scale of a forest stand
depends on whether or not—and if so, how frequently—the overall rate of seed consump-
tion exceeds the rate of seed production (Ruscoe etal. 2005). Signicant effects of burial
and microhabitat have been published for coexisting Mediterranean oak species in Spain
(Pérez-Ramos and Marañón 2008). The highest predation rates occurred for acorns located
on the ground surface (unburied), and in the most densely vegetated microhabitats, where
rodents usually exhibit higher activity. The lowest predation rates were observed in years
and at forest sites where the estimated seed production—and consequently resource avail-
ability—was higher than average, thus supporting the predator satiation hypothesis. This
temporal pattern of higher seed predation in nonmast years has been also documented in
other studies (Hulme and Borelli 1999).
Concerning restoration practices, an important recommendation for sowing is there-
fore to bury seeds 1–3 cm deep in the mineral soil (Birkedal etal. 2010, 2009). According
to different studies (Pérez-Ramos and Marañón 2008), seed loss can thus be considerably
reduced and the establishment of seedlings favored, as the leaf litter layer and mineral Ah
horizon may improve seed performance via reduced soil temperature and water evapora-
tion and increased local humidity levels (Rother etal. 2013). Moreover, it would be better
for restoration sowing activities to focus on microhabitats with a low or moderate vegeta-
tion cover and to avoid microsites with dense shrub canopies, where rodent activity is
usually high regardless of region and forest type (Fedriani etal. 2004).
6.2.3.5 Predation by other Vertebrates
Seeds of common tree species (e.g., oak and beech) are affected by vertebrate predation
both pre and postdispersal, because they produce large seeds of high nutritional value
(Nopp-Mayr etal. 2012). In return, birds disperse acorns away from the parent tree and
create seed caches as food supply for the winter (Stimm and Böswald 1994). However,
birds (as well as rodents) also predate on seeds such as acorns and beechnuts. Other omni-
present acorn and beechnut predators are wild boar, roe deer, red deer, and many beetles
(e.g., weevil larvae), who can consume most of the primarily and secondarily dispersed
seeds (González-Rodríguez and Villar 2012).
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117Developing Restoration Strategies for Temperate Forests
6.2.3.6 Scatter Hoarding
Seed dispersal by zoochory often results in highly clumped seed deposition, with high
seed densities in some locations far away from the parent tree in areas used preferentially
by dispersers (Schupp etal. 2010). Jensen (1985) found beechnuts scatter-hoarded with a
mean number of ve seeds per cache. The typical burial site is usually located a few cm
below the soil surface close to the wall of a rodent runway. Predation on caches is gener-
ally high, but in experiments more caches survived if a surplus of seeds was offered or if
rodent numbers were reduced. Age structure of saplings revealed that most individuals
had germinated in the years following mast years. Thus, there is strong circumstantial evi-
dence that scatter-hoarding animals inuence the population biology and evolution of tree
species by predation and dispersal of seeds. In turn, the synchronous production of seeds
leads to prolonged reproduction periods in the rodent species, resulting in outbreaks.
Recent research results highlight the importance of clumped seed deposition for patterns
of seedling survivorship and recruitment. By using spatially explicit simulation models,
Beckman etal. (2012) showed that clumped seed deposition increased the probability of
seedling establishment under both insect predation (host specic bruchid beetles) and
pathogen attack (Pythium and Phytophthora), as it led to local satiation of insect seed preda-
tors and made it harder for pathogen distributions to track seeds.
6.2.3.7 Pathogens
High humidity levels at the forest oor generally favor micro-oral growth, which reduces
the aeration of seeds and results in the production of toxins (Knudsen etal. 2004), thus
causing seed rotting and reduced germination. Seeds are particularly susceptible to a vari-
ety of pathogens and suffer considerable loss of viability during storage.
The pathogen Ciboria batschiana, a fructicolous Discomycete, is a serious problem affect-
ing acorn storage, which in combination with other native fungi is responsible for poor
storability. C. batschiana can destroy up to 80% of an acorn crop and may also result in
severe losses in oak seedling populations in forests (Schröder etal. 2004). Thus, oaks bene-
t from seed dispersal, as seedling recruitment is facilitated due to a decrease in pathogen
infections following dispersal (Clark and Clark 1984). Beechnuts are affected by fungal
infection to a similar degree. Massive mortality in stored beechnuts both in Europe and
in the United States has been caused by several Phytophthora species. Mycological studies
conrm the susceptibility of beech seedlings to Phytophthora spp. (Orlikowski and Szkuta
2004). Another relevant fungus in beech storage is Rhizoctonia solani (Hietala etal. 2005)
displaying symptoms of cotyledon rot. The disease is characterized by decay resulting in
reduced failure to sprout or death after emergence.
Pythium is a genus with high pathogenicity and causes the damping-off disease of ger-
minating seeds and seedlings during storage, which is not restricted to a single species
(Augspurger and Wilkinson 2007). As numerous species of this oomycetes have been
described for nursery soils (Weiland etal. 2013), there is a potential risk of infecting resto-
ration sites in the course of planting.
6.2.4 Germination in Stressful Surroundings: A Narrow Bottleneck
6.2.4.1 Germination and Safe Site
Occurrence and timing of germination play essential roles in subsequent plant establish-
ment (Baskin and Baskin 2001; Manso etal. 2013) and are often discussed as a bottleneck
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118 Restoration of Boreal and Temperate Forests
within the demographic transition from seed to sapling (Rother etal. 2013). Seeds germi-
nate only if certain conditions are met; including the breaking of dormancy. The species-
specic maternal reserves within the seed endosperm must be mobilized to provide for
the two autotrophic cotyledons, the primary leaves, and the proliferating roots. As the
primary integrators of environmental signals (Farnsworth 2008), phytohormones enable
the nascent seedling to adapt to its surrounding conditions. For many tree species, germi-
nation itself does not depend on light conditions (Nicolini etal. 2000), and radiation is thus
not relevant until the reserves in the endosperm are depleted.
The results for seedling survivorship after germination have been widely studied
(reviewed in Goulet 1995); the seedling environment is often described as extreme (Grime
1979) and conditions can be stressful and chronic, even in forest restoration. Factors induc-
ing stressful surroundings for the initial seedling development can be abiotic (e.g., unfavor-
able light and temperature regime, drought, pH, and anoxia) or biotic (e.g., high intra- and
interspecic competition, absence of mycorrhizae, herbivores, and pathogens). The latter
often benet from the same environmental conditions that are favorable for germinating
seeds or succulent seedlings, and fungal attack and death by damping-off disease are thus
common fates.
The microsite where the germination process can be successfully completed is termed
a “safe site” (Harper 1977). Safe sites generally provide a seed with sufcient moisture,
warmth, oxygen (Baier etal. 2007), and light of appropriate quality (Smith etal. 2007).
Pathogens are absent or ineffective at safe sites. A lack of safe sites restricts germina-
tion even at many restoration sites, especially those with extensively exposed soils and,
at the other extreme, those with a dense cover of competing vegetation (Urbanska 1997;
Galatowitsch 2012).
6.2.4.2 Light
In many cases, seedling reserves are critical, especially under conditions of limited light
availability (Ammer etal. 2008b). Even small reductions in biomass accumulation may
lead to seedling mortality (Fenner and Thompson 2005). In some forest ecosystems, the
light intensity at the forest oor is close to the photosynthetic compensation point, that
is, the light intensity at which respiration is equal to photosynthesis (Modry etal. 2004;
Facelli 2008). The successful establishment in such a stressful situation is only possible if
the seedling achieves a sustained positive carbon balance; photosynthesis must exceed
respirational carbon loss (Kitajima and Myers 2008). Seedlings produced by larger seeds
(e.g.,beech) are often more shade-tolerant (Leishman and Westoby 1994) due to more abun-
dant reserves. Although seed size may not be an adaptation to limited light condition per
se (e.g., Abies alba), it may assist in avoiding mortality as a result of herbivory, desiccation,
or burial by litter.
The morphology of seedling organs is also affected by varying light availability. If
growing in shaded conditions, leaves are generally broader and thinner, because this opti-
mizes light capture (Bazzaz 1996). Most species also feature lower specic root length and
increased leaf area under these conditions (Reich etal. 1998).
6.2.4.3 Litter and Soil Organic Matter
As a boundary layer, that is, a transition zone between the atmosphere and the soil, soil
surface characteristics strongly determine microsite conditions. Over the range of a few cm,
the environmental conditions can change dramatically. The boundary layer is primarily
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119Developing Restoration Strategies for Temperate Forests
characterized by site, species-dependent litter quality and quantity, stand age, and stocking
density. Existing vegetation can alter the boundary layer conditions by intercepting radia-
tion, affecting moisture availability, and determining the thickness of the litter and humus
layers and thus the humus form (George and Bazzaz 1999; Fischer etal. 2002).
The humus form, humus content in the mineral soil, and the thickness of the litter hori-
zons are particularly crucial for overall moisture supply. The surface substrate and the
vertical depth of litter and humus accumulation in relation to the relative size of seeds
and germinants often determine whether the given site can serve as a safe site for a par-
ticular species or not. Exposed mineral soil is usually the best substrate for germination
and initial growth because of its favorable moisture supply. Although litter has no effect
on emergence (or even a positive one, see Facelli 2008), thick humus layers can consider-
ably impede seedling emergence and germination. Apart from reducing light availability
(Facelli and Pickett 1991), litter may release leachates with potentially allelopathic effects
on seedling establishment (Olson and Wallander 2002). For example, Chrimes etal. (2004)
and Mallik and Pellissier (2000) discussed these interactions based on allelopathy for Picea
abies and Vaccinium myrtillus and other dominant ericaceous understory plants.
The fate of seedlings is thus affected by seed location at the time of germination. Plants
are more successful when their seeds are near the mineral soil surface as roots grow-
ing in litter substrate can fail to obtain enough water for survival. Acorns and beechnuts
often germinate best when buried 2–3 cm in the soil, regardless of the covering material
(Millerón etal. 2013), whereas birch seeds require physical contact with ne humus mate-
rial or the uppermost mineral soil (Ah) horizon to germinate successfully (Carlton and
Bazzaz 1998; Karlsson 2001).
Thick humus layers (e.g., raw humus) may need to be reduced to promote survival
of seeds and to facilitate germination, which can be done directly by prescribed re or
indirectly by preparatory cutting. However, if the thinning intensity is too high, advance
regeneration of undesired species or competing ground vegetation may thus be promoted.
Undesired species are often more shade-tolerant than desired ones, for example, Norway
spruce (Picea abies) on wet soils where pedunculate oak (Quercus robur) is preferred or in
beech stands on sites with good nutrient status where more valuable broadleaf tree species
are preferred. In mixed stands, species composition can be altered by means of early thin-
ning that selectively removes undesirable species.
Direct treatments aiming to make the physical environment of a site more suitable for
germination are more common than preparatory cutting. These treatments are intended
to modify the microclimate, improve access to water supply by exposing mineral soil, or
eliminate competing vegetation (Morris etal. 1993). Although site preparation may inter-
fere with natural succession (Nyland 1996), its benets include the elimination of unde-
sired tree species (Gordon etal. 1995; Lautenschlager 1995) as well as of grass and herbs
which provide cover for seed predators such as mice. Measures are usually directed at
species that have established advance regeneration and where control by weeding or pre-
commercial thinning is not feasible.
Apart from mineral soil, the germination of many species is facilitated by downed
deadwood, which consists of woody debris, stumps, and overgrown deadwood (LePage
etal. 2000; Hagemann etal. 2009). This is particularly relevant at harsh sites, for example
in mountain forests or in forests with a continuous grass cover (e.g., Calamagrostis spec.,
Deschampsia exuosa, and Carex brizoides). The successful establishment of species such
as Norway spruce, silver r, sycamore, and rowan could be enhanced in high-elevation,
grass-covered areas by increasing deadwood abundance (Santiago 2000; Motta etal. 2006).
The role of downed deadwood is discussed in more detail in the next section.
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120 Restoration of Boreal and Temperate Forests
6.2.4.4 Interaction with Mycorrhizae
Many case studies, both from laboratory experiments and eld studies, show that spe-
cic mycorrhizal fungi promote seedling establishment through increased access to soil
resources (Nara 2006), drought tolerance, and resistance to pathogens, among other ben-
ets (St. John 1997). In most undisturbed European ecosystems, high root density and
the ubiquity of long-lived mycorrhizal plants lead to conditions where inoculum (both
spores and hyphae) is almost always available to newly germinated seedlings (e.g., Janos
1992; Börner etal. 1995). However, in restoration sites, especially where afforestation is
required, conditions can be different as unfavorable soil status and/or articial vegetation
structures often prevail. After a site and its vegetation have been disturbed, its soil is more
likely to have reduced and/or patchy mycorrhizal infectiveness (Janos 1992), especially for
fungi that colonize new roots predominantly via hyphae rather than spores (Borner etal.
1996). Soils of early successional forests therefore typically show a low abundance and
diversity of mycorrhizal fungi (Galatowitsch 2012).
Allen etal. (2002) noted that restoration measures typically attempt to establish late suc-
cessional vegetation by planting late-seral species in early successional soils. The benets
of mycorrhizal symbiosis are therefore generally more readily apparent in forest restora-
tion than in stands with high naturalness. Even so, plants intended for afforestation or
enrichment planting in restoration should be inoculated in the nursery with appropriate
mycorrhizal fungi, whereas an inoculation will be of little benet for plants to be estab-
lished in undisturbed forest soils.
6.2.4.5 Physical Damage to Seedlings
Even after emergence, seedlings and saplings can be subjected to substantial substrate
movement, especially during forest restoration. As the result of wind erosion, young trees
are often killed from partial root exposure, as often described for postmining landscapes
(Hüttl and Weber 2001). Yet another phenomenon also creates unstable substrates for seed-
lings: in freezing air and low surface temperatures without snow cover, seedlings can be
heaved out of the soil by ice crystals forming near the soil surface (Facelli 2008).
6.2.5 Seedling Survival and Establishment: The Fine Step to Maturity
As all autotrophic plants require the same resources (i.e., water, nutrients, and light), com-
petition is the most important process during the postemergent phase of the young tree.
Both overstory and ground vegetation reduce resource availability for seedlings, and mor-
tality is thus common during subsequent seedling development.
Competition between individual plants can be differentiated into the effect of biomass
production on resource availability and the response of individual tness to resource
limitation (Goldberg 1990). In recent years, knowledge of different strategies used by tree
seedlings to acquire and allocate resources has improved considerably, particularly for
photosynthetically active radiation (PAR; see von Lüpke 1987; Coates and Burton 1999;
Hertel etal. 2012) and nutrients (Johansson etal. 2012; Guo etal. 2013). In contrast, knowl-
edge of belowground mechanisms and their importance for seedling vitality is still rudi-
mentary (Havranek and Benecke 1978; Flaig and Mohr 1990; Ammer 2003). Belowground
resources in forests feature an extremely high variability at both micro- and macro-scales,
which is difcult to control and separate from variability in PAR (Huss and Stephani 1978;
Reed etal. 1994; Walters and Reich 1997; Finzi and Canham 2000). In particular, it is not
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121Developing Restoration Strategies for Temperate Forests
well known how inter- and intraspecic root competition inuence the survivorship of
individual roots (Rust and Savill 2000; Beyer et al. 2013). Nevertheless, species-specic
responses to the complex resource pool are the key to understand the coexistence of spe-
cies (Tilmann 1982).
Restoration measures controlling competing vegetation during the seedling estab-
lishment stage can increase soil temperature, PAR availability, and nutrient availability,
thereby improving seedling survival and growth particularly under unfavorable site con-
ditions (Brand 1991; Madsen 1995; Groot 1999). The impacts of limited PAR availability
due to competing vegetation are species specic (Küßner etal. 2000), but also depend on
interactions with other environmental resources (Lautenschlager 1999; Küßner etal. 2000).
Specic recommendations for vegetation control depend on the target tree species (Löf
2000), the dominant weed species (Lautenschlager 1995), and the site. Specifying appropri-
ate treatment intensities is not easy (Tappeiner and Wagner 1987; Cain 1991), and should
account for the difference between a competition threshold and a critical-period thresh-
old (Wagner 1999). The former refers to the vegetation density at which yield loss occurs
(Jobidon 1994), the latter to the time when vegetation control should begin to prevent yield
loss (Wagner etal. 2010, 2011).
The main aim of this chapter was to illustrate the individual stages on the path to suc-
cessful natural regeneration and to allow for a more accurate interpretation of the general
recruitment probabilities. A clear focus was set on the identication of critical environ-
mental and biological factors potentially affecting the recruitment of the progeny tree
population. Although the young stand can mirror the seed rain distribution originating
from the parental stand, its characteristics more likely will be modied by differential
seed dispersal, seed storage and germination, mortality or predation, and growth (see
Figure 6.1). This background information will help to understand the specic silvicul-
tural strategies for forest restoration presented in the following two sections, discuss-
ing restoration strategies considering the overstory structure and below-canopy stand
components.
6.3 Overstory Restoration Strategies Oriented
toward the Natural Disturbance Regime
Forest restoration measures that take place in degraded forests can take advantage of exist-
ing canopies, which are to some extent degraded, that is, altered with regard to species
composition, structure, density, and so on. The forest canopy also affects tree regeneration
below, however, and these effects may be deliberately modied by treatments. This sec-
tion describes some options of canopy treatments to facilitate forest restoration through
regeneration.
6.3.1 Emulating Overstory Conditions Originating from Large-
Scale Disturbances to Support Ecological Processes
Two main functions of large-scale disturbances (between 10 and 100 km²; Temperli
2012) in forest ecosystems have been identied as the gradual progression toward
natural forest development stages, and consequently the possibility for adaptation to
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122 Restoration of Boreal and Temperate Forests
environmental changes after the destruction of the current forest system (Mitchell etal.
2004; Walker etal. 2007). The postdisturbance, more or less time-consuming successional
process includes a broad range of subprocesses, among them mineralization, transpi-
ration, regeneration, and recolonization. The progression and quality of each subpro-
cess are inuenced by the disturbance origin and the degree of destruction of different
structural compartments. Possible abiotic causes for natural large-scale disturbances in
temperate forest ecosystems are storms, drought, res, oods, avalanches, and wet snow
(Frelich 2002), which all change the structure of the previous overstory tree layer. The
damage inicted upon overstory trees and single stems strongly differs between broken,
uprooted, and burned stands (Busing etal. 2009; Goldammer 2013; Mitchell 2013). The
same applies to large-scale biotic disturbances, caused by bark beetle attacks or fungal
infections (Seidl 2009; Netherer and Schopf 2010), because of differences in individual
tree or tree species resilience. Although the overstory tree layer is often disturbed over a
large, more or less contiguous area, the understory vegetation and the surface soil layer
are characterized by heterogeneous disturbance patches of different size (Walker etal.
2007; Busing etal. 2009; Jonášová etal. 2010). The resulting mosaic of the previous under-
story is inuenced by disturbances in a different way than the overstory, because natural
large-scale disturbances never feature homogenous damage intensities throughout the
entire disturbed area. This is mainly due to the heterogeneity of specic site conditions
such as topography, relief, soil horizonation, or groundwater level. Moreover, the dif-
ferent traits of the present ground vegetation also contribute to spatial heterogeneity
(Cater and Chapin 2000). Both categories of inuential factors increase the site specic
heterogeneity after large-scale disturbances, and thus support the formation of diverse
ecological niches (Hutchinson 1978; Honnay etal. 2002). For example, small-scale patches
and structures occur frequently following different large-scale disturbances, including
broken branches, crowns and stumps, fallen trees, uprooted and leaning trees, as well as
root plates, pits and mounds (Ulanova 2000; Brang 2005a,b). Overall, the original stand
conditions are crucial for postdisturbance ecosystem development. It can be assumed
that large-scale disturbances lead to more heterogeneous conditions in natural for-
ests than in plantation forests (Keidel etal. 2008), where the overall variability is low
due to mono-structured stand conditions and articially homogenized site conditions.
Moreover, extreme climatic conditions probably increase the frequency and risk of large-
scale storm, drought, or ood events (Rowell and Moore 2000; Dale etal. 2001). Even
though heterogeneity following large-scale disturbances will increase the diversity of
plantation forest stands; it can be assumed that the next stand generation will still be less
diverse than disturbed natural forest stands (Millar etal. 2007).
For large-scale restoration, efforts aimed at modifying disturbance regimes can result
in the support of successional processes. According to Walker etal. (2007), “succession and
restoration are intrinsically linked because succession comprises species and substrate change over
time and restoration is the purposeful manipulation of that change.” These authors argue that
restoration strategies are usually geared toward short time scales, while natural succession
processes need longer time frames to successfully develop (Thomasius and Schmidt 2004).
Taking this into account, the practical implementation of natural processes and struc-
tures associated with large-scale disturbances can be divided into primary and secondary
manipulations aiming to restore the system. Primary large-scale manipulations are asso-
ciated with considerable technical efforts and create important structures for supporting
specic successional processes. Restoration measures in this manipulation category pri-
marily affect the natural regeneration indirectly via altering the overstory conditions as
summarized in Table 6.1.
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123Developing Restoration Strategies for Temperate Forests
6.3.2 Manifold Harvesting as a Strategy for Managing
Structural and Species Diversity
Two common restoration objectives—the development of natural conditions within pro-
tected areas without any further forest utilization, or the establishment of near-natural
conditions as an integral part of silvicultural management strategies—require a combi-
nation of various structures to enhance species diversity. Restoration strategies within
protected areas (e.g., reserves and national parks) are often stratied according to zoning
categories, for example, “core zones” where forests are left to develop freely, “develop-
ment zones” dened as protected areas managed mainly for ecosystem protection, and
“ recreation zones” subjected to near-natural management concepts (e.g., Federal Agency
for Nature Conservation 2012). For national parks or reserves, restoration measures gener-
ally have only initializing character (Wojczulanis 2002; McComb 2007). Continuous resto-
ration measures are therefore mainly required for application in managed forest areas, and
TABLE 6.1
Possible Primary Large-Scale Restoration Measures Associated with Altered Overstory Conditions
Primary Restoration Measures Effects on the Regeneration Process
Complete clearing
Cutting of overstory trees and
removal of all woody material
Striving for a complete change in tree species composition due to high
environmental risks and to prevent further seed dispersal and
regeneration of undesired tree species. This procedure is typically used
for controlling invasive/alien tree species (D’Antonio and Meyerson
2002). Usually, low amounts of deadwood are left, because of the
nontarget tree species within the previous overstory
Simulated windthrow
Pulling trees down or breaking
stems using winch systems or
excavators
Decoupling and reducing overstory tree competition in favor of tree
regeneration. As a result, light, water, and nutrient availability at the
forest oor increase signicantly (Kliejunas etal. 2005; Koizumi etal.
2007). Particularly newly established light-demanding tree species,
advance regeneration and early successional ground vegetation will
benet from this measure. Root plates create pits and mounds. High
accumulations of different deadwood categories are present
Prescribed burning
Implementation of low or high
intensity burns by means of
controlled re lines
Low-intensity res kill the existing ground vegetation and reduce the
litter layer, but most of the soil seed bank (Hille and den Ouden 2005;
Goldammer etal. 2013) and the overstory trees (Kozlowski 1974) will be
unaffected. Only some trees will suffer cambium damage and
subsequent die-back, but the degree of canopy closure is largely
unchanged. It should be noted that, some tree species will be present in
the next stand generation through their ability of resprouting. Therefore,
favorable conditions for the regeneration of intermediate tree species
exist. In contrast, crown res with higher intensity destroy the overstory
trees as well as the ground vegetation and soil seed bank. Thus, light
availability at the forest oor will signicantly increase. The following
succession dynamics depend on the seed dispersal rate from
surrounding tree species (Piha etal. 2013)
Water level regulation
Technical implementation of
different topographical structures
within oodplains such as
oodplain drainage, blocking of
channels, restoration of
meandering riverbeds, and
rewetting of swamp areas
The regeneration of broadleaved tree species depends on the availability
of seed trees which are well adapted to uctuating water levels (Leyer
etal. 2012). Seed production, seed dispersal adaptations, and stream
velocity decide about the presence of different tree species in the
regeneration layer (Peterken and Hughes 1995). The composition and
the distribution of tree regeneration can be controlled by small-scale
modication of soil conditions, elevation, water level, and duration of
ooding (Deiller etal. 2003)
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124 Restoration of Boreal and Temperate Forests
must be differentiated by spatial scale to successfully combine restoration measures with
harvesting procedures. At the landscape scale, forest restoration practices should combine
manifold harvesting systems instead of implementing homogenous harvesting methods
over large areas (Lindenmayer and Franklin 2002). One of the main decits of homogenous
harvesting regimes with respect to restoration efforts and naturalness is the loss of small-
scale diversity of species and structures. Species with a low activity density need transi-
tion zones or corridors across scales to maintain their populations (Hunter 1999; McComb
2007). At smaller scales, the selection of suitable harvesting systems for restoration activi-
ties aiming to establish complex natural processes is often restricted by existing stand
structures, site conditions, and the available space. Usually, the selection of management
strategies in forest enterprises is affected by numerous external factors that are not directly
linked to the topic of restoration (Nyland 2002; Messier etal. 2013). In order to deliberately
use specic harvesting systems in forest restoration, the resulting structures or processes
must be identied (Fries etal. 1997; Kerr 1999). This section analyzes “classic” harvesting
systems and their suitability to establish or maintain near-natural structures and regen-
eration conditions (Table 6.2).
6.3.2.1 Clearcut System
Although the use and the size of clearcuts have been restricted in most temperate for-
est regions, the system is still preferentially practiced in some forest regions because
of the high degree of mechanization, low short-term costs, and simple demands with
TABLE 6.2
Overview of Typical Stand Characteristics within (a) Plantations and (b) Near-natural Forests, and
Restoration Measures Suitable for Initiating Change from (a) to (b) (marked by arrows).
(a) Plantation Forests Suitable Restoration Measures (b) Natural/Near-natural Forests
Single-species overstory Promotion and revitalization of admixed tree
species via control of crown competition
Minimal tree species admixture
Single-layer overstory Establishment of vertical and horizontal stand
structures via single-tree selection systems and
combinations of uneven-aged tree species
admixture
Single to multilayered overstory
Homogeneous canopy
closure
Combination of various differently-sized
disturbances to implement heterogeneity in
light, nutrient and water availability and
inuence inter- and intraspecic competition
Heterogeneous canopy closure
Homogeneous soil
conditions
Establishment of variable site conditions to
promote the diversity of ecological niches
available for different tree and ground cover
species
Natural, unaffected soil
conditions
Large-scale management
blocks with
homogenous treatment
Increase of the variability of treatment sizes,
methods and techniques and decrease of the size
of management blocks
Natural mosaic of successional
patches
Few selected, often not
site-adapted tree species
Selection of vital trees, well adapted to specic
site conditions; approximation to natural tree
species admixture with variable vertical and
horizontal structure
Long-term site-adapted tree
species
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125Developing Restoration Strategies for Temperate Forests
respect to management. The removal of the entire overstory leads to extreme changes
of environmental conditions (i.e., light, temperature, water, and nutrient regimes). As
a result, clearcut sites are often completely restocked using articial regeneration, par-
ticularly plantations where stocking control is an objective. Clearcutting is also used to
naturally regenerate forests where desired species are shade-intolerant. With respect to
restoration objectives and near-natural processes, clearcuts only emulate those aspects
of natural disturbances that are linked to the complete loss of overstory trees (Priewasser
etal. 2013), while—in contrast to natural disturbance regimes—important structural ele-
ments such as deadwood, small-scale soil surface heterogeneity and islands of potential
seed trees are lacking. If advance regeneration is already present prior to clearcutting,
the tree species composition of the future overstory is determined by natural conditions,
likely ltered by climate and interaction processes. Thus, clearcutting can be used as
an initial event for forest restoration oriented toward establishing natural succession
processes, as for example, practiced when converting late successional forests into non-
forest ecosystems such as meadows or heathlands (Leuschner 1994; Härdtle etal. 2009).
One relevant difference between regular clearcuts and naturally established open areas
is the presence of deadwood at these sites (Priewasser etal. 2013). Moreover, if suitable
seed trees are missing, small-scale supplementation with appropriate seeds or seedlings
is possible.
6.3.2.2 Seed Tree System
The seed tree system can be described as a “soft version” of the clearcut system with respect
to the creation of extreme environmental conditions and suitable seed trees (Kuuluvainen
and Pukkala 1989; Nyland 2002). This system is mainly used to regenerate one light-
demanding tree species throughout the entire site, but more natural modications of the
system can be easily made. Parts of or entire overstory trees can be left on site to increase
deadwood stocks (Rosenvald etal. 2008). Areas without dense regeneration of target tree
species can be left to regenerate naturally by other surrounding tree species, which will
result in an admixture of different tree species with a broader range of age and develop-
ment stages. For the seed tree system, the change from closed stand conditions to open-site
conditions is less pronounced than for the clearcut system.
6.3.2.3 Retention Tree System
When both forest practitioners and forest scientists had realized the discontinuity of the
complete clearcut system, they developed the idea of retaining a number of selected trees,
so-called retention trees to compensate for the loss of key species important for forest
ecosystems (Mitchell etal. 2007; Rosenvald and Lõhmus 2008; Lindenmayer etal. 2012).
In the retention tree system, also called reserve tree system, retention trees can create a
permanent link to original forest-adapted oral and faunal species of soil-dwelling organ-
isms, insects, mycorrhizae, or specialized seed dispersers such as small mammals and
birds (Matveinen-Huju etal. 2006; Gustafsson et al. 2010; Lindenmayer etal. 2010). This
“link function” also applies to important processes associated with typical forest condi-
tions. The shelterwood system—a special retention tree system—creates homogenous
low-density canopy conditions, which promote the establishment of dense tree regenera-
tion throughout the entire site. The regeneration of shade-tolerant tree species such as
European beech using the shelterwood reserves system has thus led to large areas with
dense homogenous beech regeneration (Wagner etal. 2010).
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126 Restoration of Boreal and Temperate Forests
6.3.2.4 Irregular Shelterwood
Without supporting activities, it is therefore impossible to integrate admixtures of other
tree species. Hence, manipulations which create irregular canopy openings to increase
tree species heterogeneity within the regeneration layer are one approach to increase
biodiversity by means of restoration measures (Raymond etal. 2009). Similarly, small-
scale preparatory cuttings can be temporally staggered to stimulate seed production by
overstory trees and to increase vertical structure. Additional cuttings within the regen-
eration layer can be used to reduce the competitive pressure on admixed tree species
with lower shade tolerance and small admixture percentage. Without additional restora-
tion measures, all harvesting systems outlined above produce even-aged tree regeneration
(Fries etal. 1997; Nyland 2002). In contrast, the following silvicultural methods are ori-
ented toward the establishment of uneven-aged tree regeneration. These also include the
two general types of group-selection methods, which reduce the degree of canopy closure
by means of gap and group-sized shelter cuttings (Sagheb-Talebi and Schütz 2002). Light
demanding pioneer tree species receive greater support by the imitation of larger natu-
ral gaps. Small-scale heterogeneity within those gaps naturally results from the spatial
within-gap heterogeneity of environmental conditions (e.g., light availability) and from
edge effects created by the surrounding border trees. The stronger the environmental
gradients, the more ecological niches can become colonized by different ground vegeta-
tion and tree species (Sagheb-Talebi and Schütz 2002; Poorbabaei and Poor-Rostam 2009).
Therefore, the exclusive use of shelterwood-group selection cutting limits the establish-
ment and growth of tree species requiring higher light availability. The adaptation of
group selection to natural disturbance variability can increase the variability of small-
scale environmental conditions as well as the dynamics of the ensuing regeneration pro-
cesses. Although group-selection methods generally feature a high exibility for use
in forest restoration, single-tree selection is often considered the preferential uneven-
aged reproduction method (Nyland 2002). However, single-tree selection systems are
often criticized for excluding light-demanding tree species (Bauhus etal. 2013; Huth and
Wagner 2013). Summarizing the possibilities for choosing harvesting systems aimed at
promoting regeneration processes in the course of temperate forest ecosystem restora-
tion, the large-scale combination of different harvesting systems, which at smaller scales
are oriented toward emulating natural disturbance regimes, is a feasible compromise
(Schütz 2002).
6.3.2.5 Emulating Old-Growth Gap Conditions for Regeneration Processes
It has long been known that canopy gaps are essential for the natural regeneration of for-
ests (e.g., Watt 1925, 1947). Compared to those parts of the forest with a closed canopy, the
resource availability at the forest oor in gaps is altered, that is, improved. This improve-
ment in availability applies to radiation (Canham etal. 1990), soil water (Gray etal. 2002),
and soil nutrients (Bauhus 1996). All of these resources are essential to tree regeneration;
the high relevance of gaps to tree regeneration is hence understood as a response of the
regeneration to increased resource availability (e.g., Beckage and Clark 2003). The occur-
rence of canopy gaps is linked to canopy “disturbance,” that is, a canopy gap is “a patch
created by the removal of the canopy” (Connell 1989). In the majority of events, the removal
of parts of the canopy means that old trees or tree crowns are partly or completely dam-
aged or destroyed. Thus, the decay of old trees that create canopy gaps is linked to the
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127Developing Restoration Strategies for Temperate Forests
rejuvenation of the forest. This association between tree decay and regeneration is inte-
grated in the framework of the so-called “gap-theory.” A comprehensive overview about
the gap-theory of forest regeneration is given by Yamamoto (1992). According to this the-
ory, forests are perceived as spatial mosaics (e.g., Remmert 1991) of various compositional
and structural phases that are changing cyclically over time, implying that canopy gaps
are pivotal to tree regeneration. Many scientists working in natural forests have adopted
the gap-theory explicitly (Zeibig etal. 2005) or implicitly (Leibundgut 1982; Korpel 1995;
Christensen and Emborg 1996).
To date, the gap-theory has proved useful in analyzing a variety of forest ecosystems
ranging from temperate deciduous forests dominated by shade-tolerant species (European
beech: Wagner et al. 2010; mixed stands: Busing 1994) to subtropical forests (longleaf
pine, Pinus palustris: Brockway and Outcalt 1998), and to tropical moist evergreen forests
(Brokaw 1985).
Within natural forests, gap size is highly variable. Runkle (1982) noted that the gap size-
frequency distribution of a forest may be approximated by a lognormal distribution, that
is, that a forest features many small and few large gaps. In natural forests, the lognormal
or near-exponential shape of the gap size-frequency distribution seems to be very similar
regardless of forest type (Foster and Reiners 1986; Wagner etal. 2010). However, differ-
ences between forests have been observed regarding the total fraction of area in gaps as
well as the average gap size (Runkle 1982; Denslow 1987).
In addition to merely providing space for tree regeneration as such, gaps are also struc-
tural elements relevant for the nontree species diversity of natural forests, for example,
for butteries (Hill etal. 2001), birds (Levey 1988), and ground ora (Hahn and Thomsen
2007). Not surprisingly, research on the regeneration ecology of forest tree species has
also very intensively focused on the relevance of gaps for diversity, particularly in mixed
stands. Two hypotheses are worth mentioning as they may help to understand the rele-
vance of canopy gaps to tree species diversity in forests: (1) the “gap partitioning hypoth-
esis” (Ricklefs 1977); and (2) the “intermediate disturbance hypothesis” (Connell 1978).
The rst hypothesis considers both the variability of the individual gap area and the
gap size-frequency distribution. The variability in gap size may serve as a template for
the niche specialization of forest tree species, thus leading to gap partitioning among
species. The latter hypothesis claims that “diversity is highest when disturbances are
intermediate in intensity or size and lower when disturbances are at either extreme”
(Connell 1978). Over time, conrming evidence has been presented for both hypotheses:
the gap partitioning hypothesis (e.g., Brokaw 1985; Denslow 1987; Abe etal. 1995; Sipe
and Bazzaz 1995) and the intermediate disturbance hypothesis (Sheil 2001). However,
there is also a remaining debate about the validity of either hypothesis (e.g., Brokaw and
Busing 2000; Fox 2013).
While the gap-partitioning hypothesis seems to be most appropriate for temperate,
low-diversity climax forests (Yamamoto 1992), the intermediate disturbance hypothesis is
most suitable for transient successional forests at nonequilibrium (Sheil 2001). An impor-
tant differentiation between disturbance regimes leading to succession and the distur-
bance regime in climax forests can be made based on disturbance intensity. Following
Yamamoto (1995), we agree upon a somewhat articial upper limit of 1000 m² for small-
scale gap disturbances in climax (old-growth) forests. More importantly, “gap distur-
bance regimes in forest dynamics may not be important in the forest communities where
the large-scale disturbance occurs at intervals shorter than the longevity of the trees”
(Yamamoto 1995). Here, we will exclusively follow the small-scale disturbance regime
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128 Restoration of Boreal and Temperate Forests
and the gap-partitioning hypothesis. Moreover, we appreciate a differentiation of niches
within a single gap reported for gaps of medium to large (but still ≤1000 m²) size (Sipe and
Bazzaz 1994; Wagner etal. 2010).
The idea “to capitalize on natural forest dynamics and gap dependency” (Hartshorn
1989) in forest management may be especially appropriate in forest restoration efforts. In
forest science, the utilization of gaps—created by either nature or man—was rst advo-
cated by Gayer (1886) for the promotion of mixed stands; and as early as 1927, Wiedemann
reported about articial gaps used in experimental forest research. Recent approaches to
emulate the gap traits of natural forests in forest management have been described by
Coates and Burton (1997). Single-tree-selection, group-selection, and irregular shelter-
wood cutting come to mind as being appropriate silvicultural tools for implementing a
gap-based approach at the stand level.
Emulating gap dynamics for the purpose of forest restoration, however, means more
than simply cutting patches in forest canopies. This holds even more true if we agree on
the objective of restoration as being “to reinstate ecological processes, which accelerate
recovery of forest structure, ecological functioning, and biodiversity levels toward those
typical of climax forest” (Elliott etal. 2013). Following this deterministic perspective, the
emulation of gap dynamics is a measure which unavoidably becomes easier to successfully
implement when the forest state is closer to climax conditions. In particular, this refers to
the tree species and age distribution of the respective forest, because these are the struc-
tural components which would be most affected by the implementation or alteration of
gap dynamics. Both mentioned aspects are well understood by forest science: the trans-
formation of even-aged into uneven-aged forests aimed at prolonged and selective regen-
eration cuttings (Schütz 1999); and group-selection cuttings are designed for regenerating
mixed forests stands (Vanselow 1949; Nyland 2002; Wagner etal. 2010). The feasibility of
gap-based concepts in forestry is indicated by work of Hagemann etal. (2013), Trotsiuk
etal. (2012), and Tabaku and Meyer (1999) who reported about the similarity of the gap
size-frequency distributions in old-growth forests and in examples of practiced close-to-
nature forestry with the same species. Even in plantation-like forests, a lognormal shape
of the gap size-frequency distribution may be observed (e.g., for spruce: see Huth and
Wagner 2006).
In an attempt to conclude on gap-based regeneration approaches in forest restoration,
two critical aspects are especially important to be mentioned:
• In stands made up of species not adapted to the particular site, for example, in
plantations of exotic species, small-scale gap-based approaches to convert by natu-
ral regeneration seem unlikely to add much to the naturalness of a stand and
are therefore questionable. However, combined with articial regeneration of
native site-adapted species, gap-based approaches may make sense to implement
uneven-aged structures.
• Small-scale gap-based approaches become easier to successfully implement the
closer to climax conditions in terms of tree species assemblage and age structure.
Following large-scale disturbances, for example, in the preclimax seral stages of
forest succession, the gap approach is questionable because most preclimax spe-
cies feature a poor ability to reduce resource availability. Gap effects with respect
to altered resource availability may therefore be small in these communities, for
example, in early successional pine forests (Bolte and Bilke 1998). When emulating
gap conditions in such forests, a range of potential problems should be kept in
mind (Table 6.3).
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129Developing Restoration Strategies for Temperate Forests
6.4 Restoration Strategies for the Active Manipulation
of Below-Canopy Stand Components
Restoration measures altering the overstory layer of forest stands also inuence all lower
layers and associated ecological processes. In general, overstory changes caused by natu-
ral disturbances or harvesting increase the below-canopy availability of light, water, and
nutrients due to the removal of dominant trees. Below-canopy restoration measures can
be used to improve resource availability for target tree species and to directly promote
their establishment. But considering that restoration measures within forest ecosystems
strive to enhance diversity of different compartments, it is necessary to keep in mind that
TABLE 6.3
Questions, Problems and Recommendations When Emulating Gap Conditions
Questions Problems Recommendations
Are there risks in
implementing
selection cuts for
the rst time in a
stand with formerly
closed canopy?
As canopy openings increase air
turbulence and wind loading of the
remaining trees (Panferov and
Sogachev 2008), wind-throw
disturbance may result, which would
be quite different from natural events.
A high vitality and stability of the
individual trees of the respective stand is
required (e.g., Röhrig etal. 2006)
Are there differences
between man-made
and natural gaps
(Schliemann and
Bockheim 2011)?
Soil disturbance and biomass removal
differ between articial and natural
gaps. The latter refers especially to
‘gap-makers’ in natural forests, which
are those—often old and large—tree
individuals that create canopy gaps as
a result of damage or death. In
managed forests, gap-makers are cut
and harvested.
Gap-makers should not always be
removed from the forest during
restoration measures. Crown damage,
girdling and pulling down are
appreciable alternatives to true ‘cutting’.
Which consequences
for management
result from shifting
the cutting regime
to a gap-based
concept?
Periodic selection cuts may have to be
repeated for a very long period of time,
for example, for the next 100 years, and
this may pose management obstacles
(but will be cost-intensive).
Extreme reductions of canopy density in
a single cut tend to shift the forest to
preclimax condition and should thus be
reconsidered.
The intensity of a single cut, that is, the
removal of canopy trees, should be based
on the fraction of forest area in canopy
gaps under old-growth conditions. As gap
birth rates per year in old-growth forests
may vary (e.g., 0.5%–2% per year for
mesic forests of Eastern North-America;
Runkle 1982) and the interval between
consecutive cuts should be at least 10
years, the canopy fraction to be removed
in one cut may also vary (e.g., a gap birth
rate of 1% per year and a 10-year cutting
cycle would lead to approx. 10% of
canopy removal in a single cut).
Which trees should
be cut?
The diameter and the spatial pattern of
the cut trees determines the nancial
outcome of the restoration measures as
well as the ecological consequences and
may lead to undesired results.
Proposed selection criteria are: tree species
(predominantly undesired species),
vitality (preferentially dominant
individuals), and spatial pattern
(irregular distribution appreciated). In
addition, where advance regeneration of
native species occurs, canopy trees may
be cut to vitalize the regeneration.
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130 Restoration of Boreal and Temperate Forests
overstory manipulations indirectly affect tree regeneration. Particularly for the early tree
regeneration stages, ground vegetation and its interactions with tree seedlings are impor-
tant for successful establishment of tree regeneration. Further, the denition of target tree
species for a given forest stand needs to consider the site-specic options for articial
restoration measures, which might be used to enrich the current system, to expedite the
process of near-natural development, or simply to ensure regeneration success. For addi-
tionally supporting the regeneration of target tree species, individual measures at smaller
scales can be used and underpinned with specic knowledge drawn from the regeneration
cycle. Regeneration can also be facilitated through the availability of deadwood, a compo-
nent whose ecological role in natural forest ecosystems has been described by numerous
studies.
6.4.1 Emulating Large-Scale Disturbances to Support Ecological Below-Canopy Processes
Although primary and secondary large-scale restoration measures are interlinked, it is
helpful to clearly differentiate between them to identify the key ecological processes that
can be inuenced through specic treatments. Secondary large-scale manipulations use
existing below-canopy structures established by primary overstory manipulations and try
to increase the quality or rate of specic processes. In this context, the recolonization of
ground vegetation or tree species depends on the quality of the soil seed bank, which is
strongly inuenced by primary manipulations. While changes in the existing soil seed
bank are low after wind-throws, the effect of wildre depends on factors including rate
of spread, intensity, and duration (Piha etal. 2013). Ground res of low intensity can favor
the regeneration process by reducing litter layer depth and competing ground vegetation
(Hille and Ouden 2004; Balandier etal. 2006). This gives rise to an accelerated mineraliza-
tion and exposes mineral soil, thus facilitating the establishment of pioneer species. But as
Ryan (2002) pointed out, res vary greatly in space and time, which makes their outcomes
hard to predict. Further, in areas as densely populated as Europe, the use of large-scale re
restoration is problematic with respect to economic efciency and social acceptance (Hille
and Ouden 2004; Král etal. 2012). Moreover, a re will likely destroy any desired advance
regeneration—in contrast to simulated wind-throws—even if the resprouting potential of
many tree species is often underestimated. On restoration sites where a wind-throw has
occurred, only slight changes of former ground vegetation structures and regenerated tree
species can be expected. The enrichment with pioneer tree species (such as birch, willow,
poplar, and larch) and thus the succession process itself will be slow.
The restoration of temperate oodplain forest ecosystems calls for very specic mea-
sures aiming to reestablish natural water level uctuations over large areas along rivers
and streams (Leyer etal. 2012). According to Peterken and Huges (1995) restoration mea-
sures are connected with uvial processes and geomorphologic features and linked to the
different vegetation types of particular forest ecosystems. Combinations of natural repro-
ductive and vegetative regeneration processes are also described as suitable restoration
methods for such areas (Deiller etal. 2003).
Numerous different combinations of the primary and secondary restoration measures
listed in Table 6.4 are possible and applied in restoration practice including typical features
of possible secondary large-scale measures and their effects on the regeneration process.
The use of planting and sowing is well established in forest management and has also
been an important restoration practice for several decades. Both techniques are character-
ized by a high degree of exibility with respect to site conditions, tree species admixture,
spatial heterogeneity, and growth potential. Depending on the primary manipulation, the
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131Developing Restoration Strategies for Temperate Forests
TABLE 6.4
Possible Secondary Large-Scale Restoration Measures Manipulating Below-Canopy Conditions
Secondary Restoration Measures Effects on the Regeneration Process
Planting
Introduction of site adapted and
natural tree species. Creation of
near-natural admixtures by the
use of successful plant
assortments and densities
Planting is possible after all primary restoration measures, but requires
different efforts (Zerbe and Wiegleb 2009). Planting in wind-thrown sites
among broken trunks is more complicated than in drained sites. Future
tree species composition can be directly determined (Olsthoorn etal.
1999). The remaining overstory trees and their condition decide about the
growth increment and the survival rate of the planted tree species.
Small-scaled patches (e.g., pits and mounds) can be considered.
Direct sowing
Introduction of site-adapted and
natural tree species
For successful sowing, soil preparation is generally required to reduce
above- and below-ground competitive pressure. The planning of species
admixtures is possible, but hardly predictable as germination depends
strongly on soil surface and microclimate conditions (Cole etal. 2011).
The realization of species-specic growth edges is sometimes more
complicated than for planted species (Löf etal. 2004; Birkedal etal. 2010).
Sowing densities should be adapted to the surrounding site conditions
(Kutscher etal. 2009).
Nurse plants
Promoting plants that have
positive effects for target tree
species establishment and
recovery
Following the stress-gradient hypothesis, the use of nurse plants after
large-scale disturbances increases the survival, germination and growth
rate of target tree species (Siles etal. 2010). The establishment of specic
nurse plants (e.g., shrubs, grasses, or mosses) can buffer unfavorable
postdisturbance climate or site conditions. It is important to note that
benets for tree species regeneration from nurse plants depend on site
characteristics, species-specic interactions, individual distance from
nurse plants and the regeneration stage of target tree species (Padilla and
Pugnaire 2006).
Soil preparation
Establishment of humus and
mineral soil mixtures to reduce
the inhibitory effect of ground
vegetation
Large-scale soil disturbances diminish the competitive pressure of ground
vegetation. The loosening of the surface layer also increases nutrient
availability, water, and root permeability for tree seedlings (Löf etal.
2006). Large-scale soil preparation also inuences the surface climate of
the disturbed sites (Kubin and Kemppainen 1994). Following soil
preparation (e.g., plowing), natural regeneration, sowing, and planting
are options for establishing target tree species. The techniques are
manifold: Strips, bands, and spots in some cases are preferred to full-areal
treatment to minimize the surface area affected by the treatment. The
degree of mechanization depends on overstory conditions and the
amount of deadwood.
Mowing
Cutting the above-ground
biomass of competing ground
vegetation
Mowing interrupts the above-ground competition of ground vegetation
and thus increases the probability of successful tree species establishment
by natural regeneration, sowing or planting. As root competition is
retained, mowing measures usually have to be repeated (Willoughby
etal. 2009). The degree of mechanization depends on overstory
conditions and the amount of deadwood.
Grazing
Reducing the above-ground
biomass of ground vegetation
The reduction of above-ground competing biomass can lead to better
seedling establishment, if the regenerated tree species are not preferentially
browsed by the grazing animals. Low intensity grazing supports also the
resprouting and owering of specic ground vegetation species (Adams
1975; Kuiters etal. 1996), which makes this procedure suitable for the
restoration of open areas within forests or for orchard meadows.
Mulching
Application of organic materials
at the soil surface
Forest restoration methods use different mulch materials originating from
plants (e.g., leaves, wood, and bark chips). The mulch layer decreases the
competition by ground vegetation, the loss of nutrients, and protects the
soil surface layer against drought or erosion. A loose mulched soil surface
can promote seed germination and the primary growth of tree seedlings
(Haywood 2000).
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132 Restoration of Boreal and Temperate Forests
applicability of planting or sowing must be weighed against the technical and economi-
cal effort (e.g., in the case of high deadwood abundance). Planting and direct sowing can
be implemented as an important part of large-scale restoration even without overstory
manipulation (Zerbe 2002; Birkedal etal. 2010). However, intense primary manipulations
within the overstory tree layer increase light and water availability for planted or sown
tree species as well as for ground vegetation (Ammer etal. 2002; Table 6.4). Taking this into
account, planting can be adapted accordingly with respect to plant spacing and choice of
assortment. Primary manipulations such as prescribed burning lead to a distinct tempo-
ral head start for the planted tree species and generally decrease competitive pressure. In
most cases, successful direct sowing requires additional surface manipulation, for exam-
ple, mowing or plowing, but seedlings may be better adapted to specic site conditions
(Kutscher etal. 2009; Cole etal. 2011).
The degree of mechanization of large-scale planting or sowing depends on the remain-
ing overstory density as well as on the amount and distribution of downed deadwood.
This also applies to mowing or soil preparation (Kubin and Kemppainen 1994; Löf etal.
2006; Willoughby and Jinks 2009). Although this approach results in lower restoration costs
for primary establishment, the renewed homogenization of site conditions is problematic.
Intemperate forest ecosystems, intensive soil preparation was often used for the restoration
of extremely air-polluted forest sites (Kozlov etal. 2000).
The use of grazing as a continuous large-scale disturbance is mostly connected with
the conversion of a forest ecosystem into nonforested ecosystems (Bengtsson etal. 2000),
while periodic grazing under a light shelter of tree species favors owering ground veg-
etation and can be used for restoring orchard meadows as a specic element of forest
ecosystems (Adams 1975; Putman 1996; Tasker and Bradstock 2006). Mulching is also typi-
cally practiced in open landscapes, but successful examples for the establishment of tree
regeneration are given by Haywood (2000) and Blanco-Garcia and Lindig-Cisneros (2005).
A specic mulching strategy applying an admixture of mulch material and seeds was
described by Krautzer and Klug (2009).
The use of nurse plants to restore forest ecosystems after large-scale disturbances is
frequently used in harsh climates (Callaway 1995; Castro etal. 2002). However, even in
the temperate zone, large-scale disturbances (and restoration measures such as complete
clearings) can lead to extreme site conditions (e.g., slopes and dry sites), where the facilita-
tive function of specic ground vegetation can be used to accelerate succession processes
and tree species establishment (Padilla and Pugnaire 2006). For this purpose, it is neces-
sary to have detailed information about species-specic interactions (Siles etal. 2010) and
potential nurse plants must be established or exist within the soil seed bank. Such nurse
plants need to have a higher natural recovery potential (e.g., vegetative or generative devel-
opment strategies) than tree species regeneration (Rent etal. 2010).
6.4.2 The Function of Ground Vegetation: Facilitation Versus Competition
Compared to boreal and tropical forest ecosystems, the overall diversity of most temper-
ate forests and their oral and faunal elements are described as medium and inherently
limited by nature (Ricklefs 1977; Thomas and MacLellan 2004). Although the terms used
to describe the lower layer of forest ecosystems vary (e.g., ground vegetation, ground
cover, understory vegetation, herbaceous layer, ground layer, etc.), only two fundamental
approaches have been used to describe and quantify its functions and processes in for-
est ecosystems. Both classications are based on the hierarchy of vertical layers or strata
(Gillam 2007; Owens 2007). The rst approach involves all vascular plants with an absolute
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133Developing Restoration Strategies for Temperate Forests
height of 0.5–2.0 m (Gilliam and Roberts 2003), with the moss layer mostly separated (e.g.,
Barbier etal. 2008). The second approach combines the vertical hierarchy with a classica-
tion regarding future development. “Resident species” will never outgrow (i.e., become
higher than) the dened lower stratum (see Figure 6.2). In comparison, “transient species”
(i.e., tree regeneration) have a high potential to grow into the overstory layer (Gilliam and
Roberts 2003). Even though this approach seems to be plausible within a development-
oriented analysis of forest ecosystems, the term “resident species” can be confused with
the way it is used in the context of invasive species (Pyšek etal. 2012).
6.4.2.1 The Role of Ground Vegetation in Natural Forests
Ground vegetation is inuenced by local climate and abiotic conditions (e.g., temperature
and precipitation, soil nutrient, and water availability). Without human impact, typical
ground vegetation communities and the abundance of specic species are primarily deter-
mined by the site potential (Gracia etal. 2007). The biodiversity of ground vegetation in
temperate forests is much higher than found in the overstory tree layer (Gillam 2007).
Restoration measures aimed at the ground vegetation layer are frequently associated with
the protection of a particular rare species, for example, orchids (Hermy etal. 1999; Honnay
etal. 2002; Dorland and Willems 2006), which is deemed possible by means of modied
forest management or manual regulation of ground vegetation. However, the preserva-
tion of complete plant communities requires complex measures at larger spatial scales
(Honnay etal. 2002). As a result of increasing ground vegetation diversity in entire eco-
systems, ecological niches for soil dwelling organisms, insects, and herbivores will also
become more abundant (Hutchinson 1978; Gilbert and Lechowicz 2004; Silvertown 2004).
The ground vegetation can provide information about the potential natural vegeta-
tion (pnV) of a site and thus the degree of naturalness. Often, the locally dened pnV
is used to determine the theoretical framework for restoration objectives and guide res-
toration activities (Zerbe 1998). Ground vegetation species can thus be regarded as the
“historical memory of ecosystems” (Oheimb etal. 1999; Härdtle etal. 2003; Verheyen etal.
2003). Furthermore, ground vegetation responds quickly to changes in site conditions, for
Intra-hierarchical
competition
Facilitation
t
t
r
r
r
t
t
t
t
r
Inter-specific competitionIntra-specific competition
Inter-hierarchical competition
FIGURE 6.2
Overview of the hierarchical interaction levels in temperate forest ecosystems; and the differentiation between
transient (t) and resident (r) plants. (From Gilliam, F.S. and M.R. Roberts. 2003. The herbaceous layer in forests of
eastern North America. New York: Oxford University Press.)
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134 Restoration of Boreal and Temperate Forests
example, atmospheric depositions, habitat fragmentation, edge effects, and disturbances
(Nabuurs 1996; Hermy etal. 1999; Bossuyt and Hermy 2000; Gaudio etal. 2008), causing
large shifts in dominance of ground vegetation species as well as the abundance of alien
species (Zerbe and Kreyer 2007).
In order to interpret ground vegetation characteristics and to distinguish the environmen-
tal factors driving its vitality, growth, and abundance; different theoretical indicators (e.g.,
light or soil humidity described by indicator values (Ellenberg 1996)) have been developed.
Ground vegetation has been used as an indicator for classifying forest ecosystem status and
guide for management based on decisions (Carignan and Villard 2002; LaPaix etal. 2009).
Ferris and Humohreyn (1999) divided this indicator function into three main categories,
differentiating (1) compositional diversity (number of plants within a dened area), (2) struc-
tural diversity, and (3) functional diversity. Applying these categories, numerous studies in
natural and near-natural temperate forests have shown that site and stand structures can
be described as spatial and temporal heterogeneous patches or mosaics (Korpel 1995; Bobiec
etal. 2000; Emborg etal. 2000). A higher diversity of the overstory trees does not automati-
cally lead to a higher diversity within the ground vegetation (Gilliam and Roberts 2003;
Gillam 2007; Mölder etal. 2008). Ground vegetation has the important role of quickly recolo-
nizing, covering, and protecting the exposed mineral soil (Pyšek 1993; Honnay etal. 2002;
Royo and Carson 2006). Manifold combinations of ground vegetation and tree regeneration
result from this early successional function (Bazzaz 1996; Brang 2005a; Walker etal. 2007).
6.4.2.2 Interactions between the Different Hierarchical Strata of Forest Ecosystems
For a long time, natural forests without any human impact have been rare or almost non-
existent in the temperate climate zone. Therefore, species composition and abundance
within the ground vegetation layer has also been shaped by human alteration of the tree
layer (Økland etal. 2003; Paquette 2006; Denner 2007). Plant–plant interactions can have
competing or facilitating characteristics (Bazzaz 1996; Wagner etal. 2011). Competition and
facilitation effects across different hierarchical layers within one ecosystem are termed as
inter-hierarchical (see Figure 6.2); those within the same hierarchical layer as intra-hierarchical
(Goldberg and Landa 1991; Casper and Jackson 1997). Competition between individuals of
the same species is dened as intraspecic; competition between individuals of different
species as interspecic (Bazzaz 1996). These interactions between different strata and devel-
opment stages lead to a complex system of competing and facilitating plant actors within
forest ecosystems (Casper and Jackson 1997).
The dominance of overstory trees is obvious for those resources and environmental
factors which are dependent on vertical gradients and growth space (Table 6.2). Under
continuous forest cover, overstory trees thus determine the environmental conditions
and resource availability for ground vegetation as well as for tree regeneration (Sydes
and Grime 1981; Augusto et al. 2003; Økland etal. 2003; Penne etal. 2010). Impacts of
overstory trees are mostly associated with light transmittance (van Oijen et al. 2005;
van Couwenberghe etal. 2010, 2011; Wagner etal. 2011), precipitation interception, and
throughfall (Bredemeier etal. 2011), litter accumulation (Carli and Drescher 2002; Augusto
etal. 2003), ne root density in the humus layer (Ammer and Wagner 2005; Meinen etal.
2009), and mycorrhization (Hunter and Aarssen 1988; Luoma etal. 2006). Despite strongly
reduced resource availability at the forest oor, ground vegetation species show special
adaptations to these conditions, for example, underneath dense beech canopies (Nagaike
etal. 1999; Gilbert and Lechowicz 2004; Silvertown 2004; Gaudio etal. 2008). According to
Härdtle etal. (2003) and Nagaike etal. (1999), the diversity of ground vegetation in such
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135Developing Restoration Strategies for Temperate Forests
systems is not hindered by low light availability. Besides the unfavorable effects of com-
petition, some positive effects of overstory trees are also known, for example, the shelter
function which mitigates extreme climate conditions such as late spring frosts (Hunter and
Aarssen 1988; Nyland 2002). These positive inuences caused by tree species or ground
vegetation are dened as facilitation effects (Padilla and Pugnaire 2006; see Figure 6.2).
The importance of facilitation effects generally increases with increasingly unfavorable or
harsh environmental conditions (Freestone 2006; Paquette and Messier 2011). Within tem-
perate forest ecosystems, facilitation has been particularly observed as a part of early tree
development stages (Jensen 2011).
6.4.2.3 Using Ground Vegetation to Promote or Discriminate
Against Specic Tree Regeneration
The previous sections have shown a complex system of linkages between overstory tree
composition, ground vegetation, and site conditions. In order to integrate ground vegeta-
tion and tree species regeneration into restoration strategies, concise objectives need to be
dened, such as the increase of ground vegetation diversity, specic ground vegetation
assemblages (distributions), or the promotion of ground vegetation that facilitates tree spe-
cies regeneration (Bakker etal. 2000). The dominance of certain ground vegetation groups
is a typical phenomenon of intensively managed forest ecosystems (Paquette etal. 2006;
Gaudio etal. 2008). It can be assumed that in managed forests or forest plantations (even-
aged, single-layered stands; see Table 6.2), the homogenization of site and stand conditions
also results in the homogenization of ground vegetation (Zerbe and Brande 2003; Bauhus
and Schmerbeck 2010). Restrictions on the use of herbicides for competition control limit
the number of active measures to manipulate ground vegetation. Willoughby and Jinks
(2009) compiled a list of ground vegetation types (i.e., grasses or monocotyledons, dicotyle-
dons, pteridophytes, and woody species) that are disproportionally abundant in managed
European forests (i.e., Deschampsia sp., Calamagrostis sp., Carex sp., Pteridium sp., Epilobium
sp., Senecio sp., Urtica sp., and Rubus agg.). All of these are considered potential inhibitors
of successful tree regeneration (Löf and Welander 2004).
Local management strategies to reduce ground vegetation dominance mostly include the
use of mechanical tools such as plows, mulchers, or cultivators (Löf etal. 2012; Ammer etal.
2009; Ammer etal. 2011). These activities primarily inuence soil conditions and microto-
pography and reduce the above- and belowground competitive pressure on tree regenera-
tion (Balandier etal. 2006; Metlen and Fiedler 2006). Other restoration activities focusing on
aboveground conditions are mowing, trampling, grazing, and prescribed burning (Adams
1975; Vanha-Majamaa and Tuittila 1996; Hille and den Ouden 2005; Vandenberghe etal.
2006; Král etal. 2012). Subsequent sowing with near-natural herbaceous plant or tree spe-
cies are other possible restoration methods (Roovers etal. 2005). Light-demanding seed-
lings (e.g., Quercus spp.) need a growth edge compared to the competing ground vegetation
(Lorimer etal. 1994; Davis etal. 1998; Jensen 2011), while shade-tolerant tree species (e.g.,
Abies alba Mill.) can survive high aboveground competitive pressure by dominating ground
vegetation for longer time periods (Leibundgut 1984; Grassi and Giannini 2005).
Compared to aboveground competition (Harmer etal. 2012), the regulation of below-
ground competition between tree species regeneration and ground vegetation by means
of direct belowground measures or overstory management is more complicated. Tree spe-
cies with fast growing taproots and dense ne root networks are competitive under water
stress (Pallardy and Rhoads 1993; van Hees 1997) but most competitive ground vegetation
species readily resprout and survive aboveground damage (Mallik and Gimingham 1985;
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136 Restoration of Boreal and Temperate Forests
Fotelli et al. 2001; Klimešova and Klimeš 2007). Early successional pioneer tree species
show a similar potential of vegetative response if environmental conditions are suitable
(Koop 1987; Mallik 1997). However, even a short window post-cutting without compet-
ing ground vegetation can be sufcient to offer an advantage for tree regeneration. A
more integrated restoration strategy based on silvicultural management options includes
the utilization of pioneer nurse crops and the manipulation of overstory canopy closure
(Augusto etal. 2003; Wagner etal. 2011; Paquette and Messier 2011).
6.4.3 Direct Control of Species Composition by Establishing Artificial Regeneration
Natural regeneration can be augmented with articial regeneration when important species
are lacking or when density or spatial distribution of the natural regeneration is unsatis-
factory. These conditions are also of concern in managed forests and measures to remedy
the conditions are termed enrichment or sowing, or reinforcement planting (Nyland 2002).
There is plenty of experience with enrichment measures in managed forests as restoration
plantings in Europe have involved beech (Ammer etal. 2008a), silverr(Wiedemann 1927),
and oak species (Mortzfeldt 1896). This section will focus on the effects of the old stand on
the regeneration and the effects of the regeneration technique itself, that is, sowing versus
planting.
The ideal planting material is adapted to the soil and site, and suitable for the chosen
method and time of planting. Two types of nursery material are available: bareroot and
container seedlings. Either type may provide good results given appropriate handling and
cultural practices. In general, more intensive measures are necessary in more extreme situ-
ations, such as caused by competing vegetation, herbivores, drought, or high ground water
table. Special preparation methods for the exact planting location and a careful choice of
high-quality planting material might prove necessary.
The planting of wildlings is another way to establish desirable species. Wildlings may
have fewer establishment problems under the canopy of an old stand than standard nurs-
ery stock, as they are already adapted to shade by physiological conditioning under an
overstory (Nörr etal. 2002). Moreover, wildlings may be less prone to browsing damage as
deer often preferentially browse well-watered and fertilized nursery stock (Suchant etal.
2000). Wildlings need careful selection and handling, however, to protect leader shoots
and obtain a sufcient mass of ne roots.
In many cases, a moderate residual canopy can have positive effects on the height incre-
ment of the regeneration (Paquette etal. 2006; Balandier et al. 2007). Moderately dense
canopies may favor tree regeneration over aggressive shade-intolerant graminoids or
forbs, particularly for shade-tolerant and intermediate shade-tolerant tree species (Wagner
etal. 2011). Successful enrichment measures have been reported for irregular shelterwood
and gap-based approaches with predominantly small- to medium-sized canopy openings
(Parker etal. 2001; von Lüpke and Hauskeller-Bullerjahn 2004). The effects of canopy den-
sity on ground vegetation were discussed above.
Sowing has some advantages compared to planting for restoration as the latter does not
always guarantee site-adapted and near-natural root development (Ammer and Mosandl
2007). As successful sowing is also cheaper than planting, it may be worth trying. Sowing
by broadcast, strip, or spot techniques (Nyland 2002) is generally recommended at the
beginning of the growing season in order to reduce the risk of seed predation, fungal
infection, or unfavorable environmental conditions such as excess moisture or heavy frost.
The probability of success increases if seeds are pretreated (e.g., by stratication or incuba-
tion) to obtain prompt and vigorous germination (Stoehr and El-Kassaby 2011). Moreover,
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137Developing Restoration Strategies for Temperate Forests
seeds may be treated with repellents to control predation. Soil scarication can be used
to prepare a site for articial sowing, which may be mechanized, such as practiced for
beechnuts or acorns in drills or spots (Leder etal. 2003), as well as sowing of acorns in hoe
strips (Preuhsler and Pinto da Costa, 1994). However, machine-sowing can cause injuries
in shallow-rooted old stands, particularly in spruce, whereas this is rarely a problem in
pine stands. As the germinants and the seedlings of small-seeded conifers are particu-
larly tiny and prone to environmental stressors, a careful investigation of sowing tech-
niques and appropriate stand conditions in advance of sowing measures is recommended
(Hamm etal. 2014).
6.4.4 Manipulating the Small-Scale Seedling Environment
Almost all manipulation measures described above can be transferred to smaller spatial
scales, but they differ regarding the application of the restoration techniques. The degree
of mechanization decreases if manipulations aim for immediate environmental changes
in the vicinity of individual or small groups of seedlings. For natural or near-natural for-
est conditions, typical gap size distributions resulting from natural disturbance regimes
have been described (Runkle 1985; Mountford 2001) and have shown that small gaps
caused by the loss of single or small groups of overstory trees dominate unmanaged
forest conditions (Lorimer 1989). Manipulating the seedling environment at small scales
starts with changing overstory density by establishing variable numbers of gap creators
and gap shapes (Schütz 2002; Wagner etal. 2011). Particularly in the center of canopy
gaps, competition with an overstory for resources is reduced, resulting in improved
growth and vitality of tree seedlings. As light-demanding tree species will be dispro-
portionately favored with increasing gap size (Huth and Wagner 2006), small parts of
a forest stands can be transferred “back” to earlier successional stages, thus increasing
overall species diversity. In contrast, intermediate and shade-tolerant tree regeneration
shows a high competitive ability and potential for survival in smaller gaps or at the
edges of larger gaps.
Gap creation for restoration can enrich tree species diversity and vertical structures
at small scales (Brokaw and Busing 2000). However, periodical regulation is required to
preserve intensive seedling admixtures and prevent highly competitive tree species from
dominating over time (Petritan etal. 2007). The diversity of small-scale niches must there-
fore be continuously preserved by diverse restoration measures, if a maximum small-scale
structural diversity is the objective (Grubb 1977).
Small-scale manipulations can be based on different development stages throughout
the regeneration cycle (Figure 6.1). To begin with seed trees, seeds and the soil seed
bank, the opportunities to increase the degree of naturalness within these development
stages seem to be limited by natural processes. Promotion and revitalization of poten-
tially rare, native target seed trees in forest ecosystems can be realized with low addi-
tional effort by using release cuttings or coppicing (Karlsson 2000). Most tree species in
temperate forest ecosystems do not build up soil seed banks for long-term storage, but
this can be different for ground vegetation species (Leck et al. 2008). Nevertheless, the
overview of literature by Bossuyt and Honnay (2008) concluded that temperate forest
soil seed banks fulll the following functions with respect to restoration processes:
(1) they provide information on the existing regeneration potential if the overstory
and/or any competing ground vegetation were removed; (2) they give an impression
about the discrepancy between the current forest conditions and the natural potential,
including the dispersal input from surrounding areas; and (3) the spatial variability of
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138 Restoration of Boreal and Temperate Forests
the soil seed bank indicates the actual species-specic diversity and dominance poten-
tial without the inuence of site conditions and interaction processes (Augusto etal.
2001). Restorative manipulations can thus aim to activate the soil seed bank by means
of small-scale disturbances, for example, through the removal of ground vegetation,
partial mixing of the humus and upper mineral soil layers, or the interruption of over-
story canopy closure (Korb etal. 2005). Another option is to transfer humus and litter
samples from natural forest sites to stands that are to be enriched (Bakker etal. 2000;
Rodrigues etal. 2009). Direct sowing on small patches is also possible (Ren etal. 2012).
Such secondary restoration measures as sporadic grazing have been shown to conserve
the soil seed bank (Chaideftou etal. 2011).
Small-scale restoration measures focus on the creation of species-specic safe sites
(Schupp 1995; Smit etal. 2006; Leck etal. 2008) by reducing the germination-hampering lit-
ter layer or ground vegetation, or by limiting the inuence of overstory trees. Unfavorable
soil conditions such as stony surfaces, mineral soil and litter accumulations, or acidic soils
must be modied. Measures for soil improvement (e.g., fertilization or liming) are useful
techniques to facilitate tree germination and to improve overall site conditions (Pabian
etal. 2012). Further, small-scale surface heterogeneity can be manually established by cre-
ating specic microtopography. For example, microclimate within small pits is character-
ized by higher soil humidity and possibly lower light availability (Ulanova 2000), while
mounds dry out faster but provide better light conditions (Carlton and Bazzaz 1998; Du
etal. 2013). Germination on or near downed deadwood or stumps can be favorable for
some species.
Light manipulation via overstory regulation represents the classical approach to pro-
tect advance regeneration. Approaches to manipulate competitors surrounding individual
trees are trampling (manual) and cutting with trimmers or brushcutters; damage to indi-
vidual target trees, such as caused by herbivory, can be reduced by fences or browsing
repellents (Côté etal. 2004; Willoughby and Jinks 2009). Special nurse plants to directly
inuence the seedling environment and to buffer small-scale climate extremes have been
used (Padilla and Pugnaire 2006). Highly specic restoration methods such as the inocu-
lation with mycorrhizae (Allen 1991; Nara 2006; see Section 6.2.4) or the establishment of
legumes (Carpenter etal. 2004; Siddique 2008) are mainly found at very small scales or
used for single plant restoration activities.
6.4.5 Utilizing Deadwood to Improve Regeneration Survival
Deadwood has long been recognized as an integral component of many forest ecosystems
with particular relevance for biodiversity (Jonsson etal. 2005; Stokland etal. 2012), carbon
and nutrient cycling (Cornwell etal. 2009; Kahl etal. 2012), structural integrity (Franklin
etal. 1987; Debeljak 2006), and forest regeneration. Regeneration is particularly facilitated
by downed deadwood (DDW), which consists of woody debris, stumps and overgrown
deadwood (Hagemann et al. 2009), and provides microsites for tree seedling germina-
tion and growth. The role of DDW as “nurse logs” for regeneration is relevant in many
forest types (Figure 6.3a), including temperate (Harmon and Franklin 1989; McGee and
Birmingham 1997; Kuuluvainen and Kalmari 2003), boreal (Hofgaard 1993), and tropical
(Lack 1991; Sanchez etal. 2009) as well as submontane (Korpel 1995; Reif and Przybilla
1995; Zielonka and Niklasson 2001; Motta etal. 2006) and montane forests (Santiago 2000).
Microsites created by DDW are especially common in natural forests where stocks are con-
tinuously replenished by gap creation and stand-replacing disturbances (Debeljak 2006;
Stokland etal. 2012).
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139Developing Restoration Strategies for Temperate Forests
6.4.5.1 How Deadwood Facilitates Regeneration
In order for the tree regeneration to be successfully establish on or near DDW, seeds must
be intercepted and retained by logs providing favorable conditions for germination, estab-
lishment, and growth. By modifying the microclimate, water, and nutrient availability,
the presence of DDW thus affects several phases of the regeneration process (Figure 6.1),
including seed interception and storage (Harmon 1989a), germination (Iijima and Shibuya
2010), and seedling survival (Szewczyk and Szwagrzyk 1996).
6.4.5.2 Seed Interception, Retention and Storage
Decaying wood generally covers <10% of the forest oor (Harmon 1989a; Zielonka 2006).
Seed retention mainly depends on the size and characteristics of the log surface (Chambers
1991; Baier etal. 2007; Bače etal. 2012). Due to a smaller surface area, narrow logs trap sig-
nicantly fewer seeds than large logs (Iijima etal. 2007). Seed retention on DDW generally
increases with progressive decay (Bače etal. 2012), and is higher for moss- or litter-covered
logs compared to logs with smooth bark or without bark (Harmon 1989a; Iijima etal. 2007).
Tree species also inuence seed retention, with better retention on logs with rough bark
such as Picea or Pseudotsuga spp. (Harmon 1989a,b; Iijima and Shibuya 2010), and higher
retention likelihood for smaller seeds (Szewczyk and Szwagrzyk 1996; Iijima etal. 2007).
6.4.5.3 Germination and Seedling Establishment
Deadwood modies species-specic seed germination rates through its surface prop-
erties, decay status, and size. Germination rates increase with log size and progressive
decay, because larger logs feature more stable moisture conditions than smaller logs
(Stokland etal. 2012). Water retention capacity of DDW is generally higher than mineral
soil and increases as decomposition progresses (Sollins et al. 1987; Zielonka 2006). The
thickness of the moisture-retaining moss cover is higher on more decayed logs (Harmon
1989a; Dynesius etal. 2010). However, seedling establishment on DDW may be impeded
by very thick moss layers preventing the extension of radicals into the substrate below
(Harmon and Franklin 1989; LePage etal. 2000), potentially discriminating between spe-
cies with different germinant size, for example, favoring Abies over Picea (Szewczyk and
Szwagrzyk 1996).
FIGURE 6.3
Spruce regeneration on decaying log in the Harz mountain, Germany (a) and yellow birch regenerating on
stump in Quebec, Canada (b).
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140 Restoration of Boreal and Temperate Forests
6.4.5.4 Seedling and Sapling Survival
Particularly for conifers, the establishment and survival of seedlings on DDW is often
better than on soil (Knapp and Smith 1982; Harmon and Franklin 1989; Szewczyk and
Szwagrzyk 1996; Kupferschmid et al. 2006), and it is most pronounced for the genus
Picea (Svoboda etal. 2010; Bače etal. 2012). However, higher seedling densities have also
been observed for hardwoods such as yellow birch (Betula alleghaniensis; see McGee and
Birmingham 1997) and rowan (Stöckli 1995). The increased survival rates of tree seed-
lings on logs is mainly an effect of decreased competition with ground vegetation com-
pared to seedlings on the soil (Figure 6.3; see Ponge etal. 1998; Ran etal. 2010; Bacˇe etal.
2012). Fallen logs can serve as a regeneration substrate until the moss mat becomes thick
enough to smother seedlings (Harmon and Franklin 1989). However, differences in sur-
vival rates cannot be entirely explained by reduced competition, indicating that seedlings
elevated on logs additionally have a lower risk of mortality from soil-borne pathogens
(Harmon and Franklin 1989; Szewczyk and Szwagrzyk 1996; O’Hanlon-Manners and
Kotanen 2004). Especially in harsh environments, DDW also promotes seedling growth
and survival by offering better conditions for the growth of benecial microorganisms
and mycorrhizal fungi (Ponge etal. 1998; Zielonka 2006), increased nitrogen availabil-
ity due to microbial xation and transport from soil to DDW (Zimmerman etal. 1995;
Brunner and Kimmins 2003) and a more favorable moisture regime than soil (Sollins etal.
1987; Ran etal. 2010). In contrast, DDW provides microsites with improved aeration on
waterlogged soils (Santiago 2000).
6.4.5.5 Protection from Browsing Damage
In addition, DDW can protect tree regeneration against herbivore browsing via physi-
cal and visual obstruction (de Chantal and Granström 2007). Similar to other refuges,
deadwood piles originating from wildres, insect outbreaks, or harvesting can impede
herbivore access to regeneration (Forester etal. 2007), thus reducing browsing damage
particularly to hardwood saplings (Grisez 1960; Rumble etal. 1996; Ripple and Larsen 2001;
de Chantal and Granström 2007; Smit etal. 2012). However, DDW refuges are not always
efcient (Fredericksen etal. 1998; Kupferschmid and Bugmann 2005; Forester etal. 2007).
The quality of protection likely depends on the dominating herbivore species as well as
on log pile characteristics such as size or branchiness (de Chantal and Granström 2007),
which is associated with disturbance type (Peterson and Pickett 1995).
6.4.6 Effects of Deadwood Properties
6.4.6.1 Abundance
As a result of climate and tree species, DDW abundance naturally differs among forest
types (Harmon etal. 2004; Christensen etal. 2005). Regardless of forest type, DDW abun-
dance in managed forests is typically drastically reduced compared to natural stands
(Hodge and Peterken 1998; Debeljak 2006; Motta etal. 2006; Meyer and Schmidt 2011), as
harvesting often removes most senescent and dead trees. Forest management also modi-
es DDW decay and size distribution (Stokland etal. 2012). As restoration aims to rehabili-
tate natural structures, processes, and species composition in modied forest ecosystems
(Bradshaw 1997), restoration measures should aim at increasing DDW abundance particu-
larly in coniferous and mixed forests where DDW provides an important regeneration
substrate (Bače etal. 2012). In addition to DDW abundance, factors such as origin, type,
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141Developing Restoration Strategies for Temperate Forests
size, and decay status also inuence the relevance of DDW for tree regeneration and other
ecological forest functions such as biodiversity (Harmon etal. 2004).
6.4.6.2 Origin and Type
Natural stand-level disturbances create large amounts of DDW immediately (storm)
or several decades (insects, wildre) following disturbance (Jonášová and Prach 2004;
Hagemann etal. 2009; Jonášová etal. 2010), while small-scale tree mortality results in the
more or less continuous creation of all sizes and types of DDW (Harmon etal. 2004). In
contrast, harvesting leaves mostly crown material and stumps (Hagemann et al. 2009;
Stokland et al. 2012). Like logs, stumps also offer microsites with reduced competition
and favorable growing conditions (Motta etal. 2006; Bače etal. 2011). Regardless of ori-
gin, stumps may even be superior to logs as seedling establishment occurs earlier and at
higher densities, likely due to better seed retention in surface depressions and faster decay
(Nakagawa etal. 2001; Bače etal. 2011). Even standing deadwood can indirectly affect tree
regeneration by accommodating birds which disperse the seeds of many tree species, such
as spruce, rowan or beech (Jonášová and Prach 2004). The cause of tree death can also
inuence regeneration density, with higher seedling densities observed on logs uprooted
or broken by wind compared to logs originating from bark beetle attacks (Bače etal. 2012).
Bark beetles facilitate the entry of brown-rot fungi (Stokland etal. 2012), and DDW decayed
by brown-rot fungi is less suitable for seedling establishment (Bače etal. 2012).
6.4.6.3 Size
It is well known that large-diameter DDW is particularly important for biodiversity, espe-
cially for saproxylic beetles, fungi and lichen (Jonsson etal. 2005; Müller and Bütler 2010;
Stokland etal. 2012). As larger logs offer more surface area for seed retention and seedling
establishment (Iijima etal. 2007; Bače etal. 2012), an increased abundance of large-diam-
eter DDW also favors the natural regeneration of conifers. Moreover, the retention and
creation of large DDW piles are recommended for protecting regeneration in areas with
high browsing pressure (de Chantal and Granström 2007).
6.4.6.4 Decay Status
The suitability of DDW as a substrate for regeneration changes over time as decompo-
sition alters its physical and chemical properties. This is reected in changing seedling
abundance, survival rates, and even physiological traits such as photosynthetic capac-
ity (Ran etal. 2010; Bače etal. 2012). Seedling density generally increases as decay with
progresses (Szewczyk and Szwagrzyk 1996; Zielonka 2006), but may slightly decreases in
the last decay stages due to increased competition among seedlings and other vegetation
(Zielonka and Niklasson 2001; Zielonka and Piatek 2004). For example, the highest number
of spruce seedlings is typically found on 30–60-year-old logs, but seedling establishment
may start as early 10 years after tree death (Zielonka 2006).
6.4.7 Deadwood and Forest Restoration
Although DDW is not the most important factor in forest regeneration (Szewczyk and
Szwagrzyk 1996), it plays an extremely large role in coniferous forests where trees regen-
erate predominantly on logs (Franklin etal. 1987; Svoboda etal. 2010). In order to facili-
tate natural regeneration in these forest types, DDW abundance could be increased by a
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142 Restoration of Boreal and Temperate Forests
range of passive or active restoration measures (Table 6.5; Stöckli 1995; Ježek 2004; Vanha-
Majamaa etal. 2007; Svoboda etal. 2010; Meyer and Schmidt 2011; Stokland etal. 2012).
However, the effects of such measures on tree regeneration will only become visible in
the medium- or long-term because DDW accumulation following abandonment of for-
est activities is a very slow process (Bobiec 2002; Vandekerkhove etal. 2009; Meyer and
Schmidt 2011) and it takes decades for newly generated DDW to become a suitable regen-
eration substrate (Zielonka 2006). Increased DDW abundance can also contribute to more
natural stand structures, as the strong association between DDW and seedling establish-
ment for some tree species results in nonrandom (i.e., linear or clumped) spatial patterns
of regeneration (Svoboda etal. 2010). However, measures to increase DDW availability
need to be supplemented by measures regulating canopy closure to ensure the successful
growth of seedlings established on decaying wood (Zielonka 2006; Svoboda etal. 2010).
References
Abe, S., T. Masaki, and T. Nakashizuka. 1995. Factors inuencing sapling composition in canopy
gaps of a temperate deciduous forest. Vegetatio 120: 21–32.
Adams, S.N. 1975. Sheep and cattle grazing in forests: A review. Journal of Applied Ecology 12 (1): 143–52.
TABLE 6.5
Restoration Measures for Increasing Deadwood Abundance
Restoration Measures Effects on Deadwood Abundance and Quality
a. Passive measures
Abandonment of forest activities Gradual creation of snags and DDW by natural
mortality (senescence, small-scale or large-scale
disturbances)
Abandonment of salvage logging Retention of disturbance-generated snags and DDW
with given variability of decay, size, and species
distribution
Retention of live (over-)mature trees Gradual creation of snags and DDW as trees are left to
die naturally over time, diversication of decay and
size distribution
Retention of standing dead trees Gradual creation of DDW as snags are left to fall
naturally over time, diversication of decay and size
distribution
Retention of logging debris Immediate creation of fresh DDW of various size
classes and species
b. Active measures
Creation of snags and high stumps (girdling, topping,
crown blow-up)
Immediate creation of fresh snags (and downed
crown material) of various size classes, species and
with desired spatial distribution
Creation of DDW (felling, pulling down, breaking,
uprooting)
Immediate creation of fresh DDW of various size
classes and species and with desired spatial
distribution
Introduction of DDW (log sections) Immediately increased availability of DDW with
desired decay, size and species distribution as
substrate for regeneration
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
143Developing Restoration Strategies for Temperate Forests
Allen, M.F. 1991. The Ecology of Mycorrhizae. Cambridge studies in ecology. Cambridge University
Press, Cambridge, New York.
Allen, C.D., M. Savage, D.A. Falk, K.F. Suckling, T.W. Swetnam, T. Schulke, P.B. Stacey, P. Morgan,
M.Hoffmann, and J. T. Klingel. 2002. Ecological restoration of ponderosa pine ecosystems:
Abroad perspective. Ecological Applications 12(5): 1418–33.
Ammer, C. 2003. Growth and biomass partitioning of Fagus sylvatica L. and Quercus robur L. seed-
lings in response to shading and small changes in the R/FR-ratio of radiation. Annales of Forest
Science 60: 163–71.
Ammer, C., P. Balandier, N. Bentsen, L. Coll, and M. Löf. 2011. Forest vegetation management under
debate: An introduction. European Journal of Forest Research 130: 1–5.
Ammer, C., E. Bickel, and C. Kölling. 2008a. Converting Norway spruce stands with beech—A review
of arguments and techniques. Austrian Journal of Forest Science 125: 3–26.
Ammer, C., M. Blaschke, and P. Muck. 2009. Germany. In: Willoughby, I., P. Balandier, N.S. Bentsen,
N. McCarthy, and J. Claridge (eds.), Forest Vegetation Management in Europe—Current Practice
and Future Requirements. COST Ofce, Brussels, pp. 43–50.
Ammer, C. and R. Mosandl. 2007. Which grow better under the canopy of Norway spruce planted or
sown seedlings of European beech? Forestry 80 (4): 385–95.
Ammer, C., R. Mosandl, H. El Kateb. 2002. Direct seeding of beech (Fagus sylvatica L.) in Norway
spruce (Picea abies [L.] Karst.) stands—Effects of canopy density and ne root biomass on seed
germination. Forest Ecology and Management 159: 59–72.
Ammer, C., B. Stimm, B., and R. Mosandl. 2008b. Ontogenetic variation in the relative inuence of
light and belowground resources on European beech seedling growth. Tree Physiology 28: 721–8.
Ammer, C. and S. Wagner. 2005. An approach for modelling the mean ne-root biomass of Norway
spruce stands. Trees 19: 145–53.
Aronson, J. and S. Alexander. 2013. Ecosystem restoration is now a global priority: Time to roll up our
sleeves. Restoration Ecology 21 (3): 293–96.
Ashley, M.V. 2010. Plant parentage, pollination, and dispersal: How DNA microsatellites have altered
the landscape. Critical Reviews in Plant Sciences 29: 148–61.
Augspurger, C.K. and Wilkinson, H.T. 2007. Host specicity of pathogenic Pythium species:
Implications for tree species diversity. Biotropica 39: 702–8.
Augusto, L., J.-L. Dupouey, J.-F. Picard, and J. Ranger. 2001. Potential contribution of the seed bank in
coniferous plantations to the restoration of native deciduous forest vegetation. Acta Oecologica
22 (2): 87–98.
Augusto, L., J.-L Dupouey, and J. Ranger. 2003. Effects of tree species on understory vegetation and
environmental conditions in temperate forests. Annales of Forest Science 60: 823–31.
Baasch, A., S. Tischew, and H. Bruelheide. 2009. Insights into succession processes by temporally
repeated habitat models: Results from a long-term study in a post-mining landscape. Journal of
Vegetation Science 20: 629–38.
Bače, R., M. Svoboda, and P. Janda. 2011. Density and height structure of seedlings in subalpine spruce
forests of Central Europe: Logs vs. stumps as a favourable substrate. Silva Fennica 45 (5): 1065–78.
Bače, R., M. Svoboda, V. Pouska, P. Janda, and J. Červenka. 2012. Natural regeneration in Central-
European subalpine spruce forests: Which logs are suitable for seedling recruitment? Forest
Ecology and Management 266 (15): 254–62.
Bacilieri, R., T. Labbe, and A. Kremer 1994. Intraspecic genetic structure in a mixed population of
Quercus petraea (Matt.) Liebl. and Q. robur L. Heredity 73: 130–41.
Baier, R., J. Meyer, and A. Göttlein. 2007. Regeneration niches of Norway spruce (Picea abies [L.]
Karst.) saplings in small canopy gaps in mixed mountain forests of the Bavarian Limestone
Alps. European Journal of Forest Research 126: 11–22.
Bakker, J.P., A.P. Grootjans, M. Hermy, and P. Poschlod. 2000. How to dene targets for ecological
restoration?—Introduction. Applied Vegetation Science 3 (1): 3–6.
Balandier, P., C. Collet, J.H. Miller, P.E. Reynolds, and S.M. Zedanker. 2006. Designing forest vegeta-
tion management strategies based on the mechanisms and dynamics of crop tree competition
by neighbouring vegetation. Forestry 79 (1): 3–27.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
144 Restoration of Boreal and Temperate Forests
Balandier, P., H. Sinoquet, E. Frak, R. Giuliani, M. Vandame, S. Descamps, L. Coll, B. Adam,
B.Prevosto, and T. Curt. 2007. Six-year time course of light-use efciency, carbon gain and
growth of beech saplings (Fagus sylvatica) planted under a Scots pine (Pinus sylvestris) shelter-
wood. Tree Physiology 27: 1073–82.
Barbier, S., F. Gosselin, and P. Balandier. 2008. Inuence of tree species on understory vegetation
diversity and mechanisms involved—A critical review for temperate and boreal forests. Forest
Ecology and Management 254 (1): 1–15.
Barnes, B.V., D.R. Zak, S.R. Denton, and S.H. Spurr. 1998. Forest Ecology, 4th edn. John Wiley & Sons,
New York.
Baskin, C.C. and Baskin, J.M. 2001. Seeds. Ecology, biogeography, and evolution of dormancy and
germination. Nordic Journal of Botany 20: 598.
Bauhus, J. 1996. C and N mineralization in an acid forest soil along a gap-stand gradient. Soil Biology
and Biochemistry 28 (7): 923–32.
Bauhus, J. and J. Schmerbeck. 2010. Silvicultural options to enhance and use forest plantation biodi-
versity. In: Bauhus, P. van der Meer, and M. Kanninen (eds.), Ecosystem Goods and Services from
Plantation Forests. Earthscan, London–Washington, DC, pp. 96–139.
Bayer, D., S. Seifert, and H. Pretzsch. 2013. Structural crown properties of Norway spruce (Picea abies
[L.] Karst.) and European beech (Fagus sylvatica [L.]) in mixed versus pure stands revealed by
terrestrial laser scanning. Trees 27 (4): 1035–47.
Bazzaz, F.A. 1996. Plants in Changing Environments: Linking Physiological, Population, and Community
Ecology. Cambridge University Press, Cambridge, New York, Melbourne.
Beckage, B. and J.S. Clark. 2003. Seedling survival and growth of three forest tree species: The role of
spatial heterogeneity. Ecology 84: 1849–61.
Beckman, N.G., C. Neuhauser, and H.C. Mueller-Landau. 2012. The interacting effects of clumped
seed dispersal and distance- and density-dependent mortality on seedling recruitment pat-
terns. Journal of Ecology 100: 862–73.
Bengtsson, J., S.G. Nilsson, A. Franc, and P. Menozzi. 2000. Biodiversity, disturbances, ecosystem
function and management of European forests. Forest Ecology and Management 132 (1): 39–50.
Beyer, F., D. Hertel, and C. Leuschner. 2013. Fine root morphological and functional traits in Fagus
sylvatica and Fraxinus excelsior saplings as dependent on species, root order and competition.
Plant Soil 373: 143–56.
Birkedal, M., A. Fischer, M. Karlsson, M. Löf and P. Madsen 2009. Rodent impact on establishment
of direct-seeded Fagus sylvatica, Quercus robur and Quercus petraea on forest land. Scandinavian
Journal of Forest Research 24: 298–307.
Birkedal, M., M. Löf, G.E. Olsson, and U. Bergsten. 2010. Effects of granivorous rodents on direct
seeding of oak and beech in relation to site preparation and sowing date. Forest Ecology and
Management 259 (12): 2382–89.
Blanco-Garcia, A. and R. Lindig-Cisneros. 2005. Incorporating restoration in sustainable forestry
management: Using pine-bark mulch to improve native species establishment on tephra
deposits. Restoration Ecology 13 (4): 703–09.
Bobiec, A. 2002. Living stands and dead wood in the Białowieża forest: Suggestions for restoration
management. Forest Ecology and Management 165 (1–3): 125–40.
Bobiec, A., H. van der Burgt, K. Meijer, C. Zuyderduyn, J. Haga, and B. Vlaanderen. 2000. Rich
deciduous forests in Białowieża as a dynamic mosaic of developmental phases: Premises for
nature conservation and restoration management. Forest Ecology and Management 130 (1–3):
159–75.
Boerner, R.E.J., G. Brent, P. DeMars, and P.N. Leicht. 1996. Spatial patterns of mycorrhizal infective-
ness of soils long a successional chronosequence. Mycorrhiza 6: 79–90.
Bolte, A. and A. Bilke. 1998. Wirkung der bodenbelichtung auf die ausbreitung von Calamagrostis
epigejos in den kiefernforsten Norddeutschlands. Forst und Holz 53: 232–36.
Bonnet-Masimbert, M. 1987. Floral induction in conifers: A review of available techniques. Forest
Ecology and Management 19: 135–46.
Bossema, I. 1979. Jays and oaks: An eco-ethological study of a symbiosis. Behaviour 70 (1/2): 1–117.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
145Developing Restoration Strategies for Temperate Forests
Bossuyt, B. and M. Hermy. 2000. Restoration of the understorey layer of recent forest bordering
ancient forest. Applied Vegetation Science 3 (1): 43–50.
Bossuyt, B. and O. Honnay. 2008. Can the seed bank be used for ecological restoration? An overview
of seed bank characteristics in European communities. Journal of Vegetation Science 19 (6): 875–84.
Bradshaw, A.D. 1997. What do we mean by restoration? In: Urbanska, K.M., N.R. Webb, and P.J.
Edwards (eds.), Restoration Ecology and Sustainable Development, Cambridge University Press,
Cambridge, UK, pp. 8–14.
Bradshaw, A.D. 2002. Introduction and philosophy. In: Perrow, M.R., and Davy, A.J. (eds.), Handbook of
Ecological Restoration, Vol. 1. Principles of Restoration, Cambridge University Press, Cambridge,
UK, pp. 3–9.
Brand, D.G. 1991. The establishment of boreal and sub-boreal conifer plantations: An integrated anal-
ysis of environmental conditions and seedling growth. Forest Science 37: 68–100.
Brang, P. 2005a. Spatial distribution of natural regeneration on large windthrow areas created by the
hurricane Lothar in 1999. Schweizerische Zeitschrift für Forstwesen 156 (12): 467–76.
Brang, P. 2005b. Virgin forests as a knowledge source for central European silviculture: Reality or
myth? Forest Snow and Landscape Research 79 (1–2): 19–32.
Bredemeier, M., S. Cohen, D.L. Godbold, E. Lode, V. Pichler, and P. Schleppi. 2011. Forest Management
and the Water Cycle: An Ecosystem-Based Approach. Ecological Studies 212. Dordrecht, New York:
Springer.
Brockway, D.G. and K.W. Outcalt. 1998. Gap-phase regeneration in longleaf pine wiregrass ecosys-
tems. Forest Ecology and Management 106: 125–39.
Brokaw, N.V.L. 1985. Gap-phase regeneration in a tropical forest. Ecology 66: 682–87.
Brokaw, N. and R.T. Busing. 2000. Niche versus chance and tree diversity in forest gaps. Trends in
Ecology and Evolution 15 (5): 183–88.
Brown, J.M.B. 1951. Inuence of shade on the height growth and habit of beech. Forestry Commission.
Report on forest research for the year ending: 62–67.
Brunner, I., E. Graf Pannatier, B. Frey, A. Rigling, W. Landolt, S. Zimmermann, and M. Dobbertin.
2009. Morphological and physiological responses of Scots pine ne roots to water vegetation
dynamics in northeastern USA. Ecology 85: 519–30.
Brunner, A. and J.P. Kimmins. 2003. Nitrogen xation in coarse woody debris of Thuja plicata and
Tsuga heterophylla forests on northern Vancouver Island. Canadian Journal of Forest Research
33(9): 1670–82.
Buchert, G.P. 1992. Genetic diversity—An indicator of sustainability. Advances Boreal Mixedwood
Management 10: 190–3.
Buiteveld, J., G.G. Vendramin, S. Leonardi, K. Kamer and T. Geburek. 2007. Genetic diversity and dif-
ferentiation in European beech (Fagus sylvatica L.) stands varying in management history. Forest
Ecology and Management 247: 98–106.
Bullock, J.M. and R.T. Clarke. 2000. Long distance seed dispersal by wind: Measuring and modelling
the tail of the curve. Oecologia 124: 506–21.
Bullock, J.M. and R. Nathan. 2008. Plant dispersal across multiple scales: Linking models and reality.
Journal of Ecology 96: 567–8.
Busing, R.T. 1994. Canopy cover and tree regeneration in old-growth cove forests of the Appalachian
Mountains. Vegetatio 115: 19–27.
Busing, R.T., R.D. White, M.E. Harmon, and P.S. White. 2009. Hurricane disturbance in a temperate decid-
uous forest: Patch dynamics, tree mortality, and coarse woody detritus. Plant Ecology 201: 351–63.
Cain, M.D. 1991. The inuence of woody and herbaceous competition on early growth of naturally
regenerated loblolly and shortleaf pines. Southern Journal of Applied Forestry 15: 179–85.
Callaway, R.M. 1995. Positive interactions among plants. Botanical Review 61 (4): 306–49.
Cameron, A.D. 1996. Managing birch woodlands for the production of quality timber. Forestry
69:357–71.
Canham, C.D., J.S. Denslow, W.J. Platt, J.R. Runkle, T.A. Spies, and P.S. White. 1990. Light regimes
beneath closed canopies and tree-fall gaps in temperate and tropical forests. Canadian Journal of
Forest Research 20 (5): 620–31.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
146 Restoration of Boreal and Temperate Forests
Carignan, V. and M.A. Villard. 2002. Selecting indicator species to monitor ecological integrity:
Areview. Environmental Monitoring and Assessment 78 (1): 45–61.
Carli, A. and A. Drescher. 2002. Die verbesserung der humusauage durch laubbäume—das beispiel
sekundärer chtenforste in der SE-Steiermark. Mitteilungen des Naturwissenschaftlichen Vereines
für Steiermark 132: 153–68.
Carlton, G.C. and F.A. Bazzaz. 1998. Resource congruence and forest regeneration following an
experimental hurricane blowdown. Ecology 79 (4): 1305–19.
Carpenter, F.L., J.D. Nichols, and E. Sandi. 2004. Early growth of native and exotic trees planted on
degraded tropical pasture. Forest Ecology and Management 196 (2–3): 367–78.
Casper, B.B. and R.B. Jackson. 1997. Plant competition underground. Annual Review of Ecology
Systematics 28 (1): 545–70.
Castro, J., R. Zamora, J.A. Hodar, and J.M. Gomez. 2002. Use of shrubs as nurse plants: A new tech-
nique for reforestation in Mediterranean mountains. Restoration Ecology 10 (2): 297–305.
Cater, T.C. and F.S. Chapin. 2000. Differential effects of competition or microenvironment on boreal
tree seedling establishment after re. Ecology 81 (4): 1086–99.
Cattarino, L., C. McAlpine, and J.R. Rhodes. 2013. The consequences of interactions between dispersal
distance and resolution of habitat clustering for dispersal success. Landscape Ecology 28: 1321–34.
Chaideftou, E., C.A. Thanos, E. Bergmeier, A.S. Kallimanis, and P. Dimopoulos. 2011. The herb layer
restoration potential of the soil seed bank in an overgrazed oak forest. Journal of Biological
Research 15: 47–57.
Chambers, J.C., J.A. MacMahon, and J.H. Haefner. 1991. Seed entrapment in alpine ecosystems:
Effects of soil particle size and diaspore morphology. Ecology 72 (5): 1668–77.
Chandler, L.M. and J.N. Owens. 2004. The pollination mechanism of Abies amabilis. Canadian Journal
of Forest Research 34: 1071–80.
Chrimes, D., L. Lundqvist, and O. Atlegrim. 2004. Picea abies sapling height growth after cutting
Vaccinium myrtillus in an uneven-aged forest in northern Sweden. Forestry 77: 61–66.
Christensen, M. and J. Emborg. 1996. Biodiversity in natural versus managed forest in Denmark.
Forest Ecology and Management 85 (1–3): 47–51.
Christensen, M., K. Hahn, E.P. Mountford, P. Ódor, T. Standovár, D. Rozenbergar, and J. Diaci 2005.
Dead wood in European beech (Fagus sylvatica) forest reserves. Forest Ecology and Management
210 (1–3): 267–82.
Ciccarese, L., A. Mattsson, and D. Pettenella. 2012. Ecosystem services from forest restoration.
Thinking ahead. New Forests 43 (5–6): 543.
Clark, D.A. and D.B. Clark, 1984. Spacing dynamics of a tropical rain forest tree: Evaluation of the
Janzen–Connell model. The American Naturalist 124: 769–88.
Clark, J.S., E. Macklin, and L. Wood, 1998. Stages and spatial scales of recruitment limitation in
Southern Appalachian forests. Ecological Monographs 68: 213–35.
Clark, J.S., M. Silman, R. Kern, E. Macklin, and J. Hille Ris Lambers. 1999. Seed dispersal near and far:
Patterns across temperate and tropical forests. Ecology 80: 1475–94.
Coates, K.D. and P.J. Burton. 1997. A gap-based approach for development of silvicultural systems to
address ecosystem management objectives. Forest Ecology and Management 99 (3): 337–54.
Coates, K.D. and P.J. Burton, 1999. Growth of planted tree seedlings in response to ambient light
levels in northwestern interior cedar–hemlock forests of British Columbia. Canadian Journal of
Forest Research 29 (9): 1374–82.
Cole, R.J., K.D. Holl, C.L. Keene, and R.A. Zahawi. 2011. Direct seeding of late-successional trees to
restore tropical montane forest. Forest Ecology and Management 261 (10): 1590–97.
Connell, J.H. 1971. On the role of natural enemies in preventing competitive exclusion in some
marine animals and in rain forest trees. In: Den Boer, P.J., and G. Gradwell (eds.), Dynamics
of Populations. Center for Agricultural Publication and Documentation, Wageningen, The
Netherlands, pp. 298–312.
Connell, J.H. 1978. Diversity in tropical rain forests and coral reefs. Science 199 (4335): 1302–10.
Connell, J.H. 1989. Some processes affecting the species composition in forest gaps. Ecology 70 (3):
560.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
147Developing Restoration Strategies for Temperate Forests
Cornwell, W.K., Cornelissen, J.H.C., S.D. Allison, J. Bauhus, P. Eggleton, C.M. Preston, F. Scarff, J.T.
Weedon, C. Wirth, and A.E. Zanne. 2009. Plant traits and wood fates across the globe: Rotted,
burned, or consumed? Global Change Biology 15 (10): 2431–49.
Côté, SD., T.P. Rooney, J.-P. Tremblay, C. Dussault, and D.M. Waller. 2004. Ecological impacts of deer
overabundance. Annual Review of Ecology, Evolution, and Systematics 35 (1): 113–47.
Crone, E.E., E.J.B. McIntire, and J. Brodie. 2011. What denes mast seeding? Spatio-temporal patterns
of cone production by whitebark pine. Journal of Ecology 99: 438–44.
Curran, L.M. and M. Leighton. 2000. Vertebrate responses to spatiotemporal variation in seed pro-
duction of mast-fruiting Dipterocarpaceae. Ecological Monographs 70 (1): 101–28.
Dale, V.H., L.A. Joyce, S. McNulty, R.P. Neilson, M.P. Ayres, M.D. Flannigan, P.J. Hanson etal. 2001.
Climate change and forest disturbances. BioScience 51 (9): 723–34.
D’Antonio, C. and L.A. Meyerson. 2002. Exotic plant species as problems and solutions in ecological
restoration: A synthesis. Restoration Ecology 10 (4): 703–13.
Davis, M.A., K.J. Wrage, and P.B. Reich. 1998. Competition between tree seedlings and herbaceous
vegetation: Support for a theory of resource supply and demand. Journal of Ecology 86 (4): 652–61.
Debeljak, M. 2006. Coarse woody debris in virgin and managed forest. Ecological Indicators 6 (4): 733–42.
de Chantal, M. and A. Granström. 2007. Aggregations of dead wood after wildre act as browsing
refugia for seedlings of Populus tremula and Salix caprea. Forest Ecology and Management 250
(1–2): 3–8.
Deiller, A.-F., J.-M.N. Walter, and M. Trémolières. 2003. Regeneration strategies in a temperate hard-
wood oodplain forest of the Upper Rhine: Sexual versus vegetative reproduction of woody
species. Forest Ecology and Management 180 (1–3): 215–25.
Denner, M. 2007. Auswirkungen des ökologischen Waldumbaus in der Dübener Heide und im Erzgebirge auf
die Bodenvegetation: Ermittlung phytozönotischer Indikatoren für naturschutzfachliche Bewertungen
(Effects of ecological forest conversion in Dübener Heide and Erzgebirge on the ground
vegetation—Determination of phytocoenotic indicators for nature conservation evaluations).
Forstwissenschaftliche Beiträge Tharandt 29. Stuttgart: Ulmer.
Denslow, J.S. 1987. Tropical rainforest gaps and tree species diversity. Annual Review of Ecology and
Systematics 18 (1): 431–51.
Dobrowolska, D., S. Hein, A. Oosterbaan, S. Wagner, J. Clark, and J.P. Skovsgaard. 2011. A review of
European ash (Fraxinus excelsior L.): Implications for silviculture. Forestry 84: 133–48.
Doody, C.N. and C. O’Reilly. 2008. Drying and soaking pretreatments affect germination in pedun-
culate oak. Annales of Forest Science 65 (509).
Dorland, E. and J.H. Willems. 2006. High light availability alleviates the costs of reproduction in
Ophrys insectifera (Orchidaceae). Journal Europäischer Orchideen 38 (2): 501–18.
Downie, B. and J.D. Bewley. 2000. Soluble sugar content of white spruce (Picea glauca) seeds during
and after germination. Physiologia Plantarum 110: 1–12.
Du, S., W. Duan, L. Wang, L. Chen, Q. Wie, M. Li, and L. Wang. 2013. Microsite characteristics of
pit and mound and their effects on the vegetation regeneration in Pinus koraiensis dominated
broadleaved mixed forest. Chinese Journal of Applied Ecology 24 (3): 633–38.
Dynesius, M., H. Gibb, and J. Hjältén. 2010. Surface covering of downed logs: Drivers of a neglected
process in dead wood ecology. PLoS ONE 5 (10): e13237.
Ellenberg, H. 1996. Vegetation Mitteleuropas mit den Alpen in ökologischer, dynamischer und historischer
Sicht: 170 Tabellen. 5., stark veränd. und verb. (Vegetation of Central Europe and the Alps with
respect to ecology, dynamic and history: 170 tables. 5th Edition) Au. UTB 8104. Stuttgart: Ulmer.
Elliott, S.D., D. Blakesley, and K. Hardwick. 2013. Restoring Tropical Forests: A Practical Guide. Kew
Publications, London.
Emborg, J., M. Christensen, and J. Heilmann-Clausen. 2000. The structural dynamics of Suserup
Skov, a near-natural temperate deciduous forest in Denmark. Forest Ecology and Management
126 (2): 173–89.
Facelli, J.M. 2008. Specialized strategies I: Seedlings in stressful environments. In: M.A. Allessio Leck,
V.T. Parker, and R.L. Simpson (eds.), Seedling Ecology and Evolution. Cambridge University
Press, Cambridge.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
148 Restoration of Boreal and Temperate Forests
Facelli, J.M. and S.T.A. Pickett. 1991. Plant litter: Light interception and effects on an oldeld plant
community. Ecology, 72, 1024–31.
Farnsworth, E.J. 2008. Physiological and morphological changes during early seedling growth: Roles
of phytohormones. In: Leck, M.A., V.T. Parker, and R.L. Simpson (eds.), Seedling Ecology and
Evolution. Cambridge University Press, Cambridge, UK, 150–71.
Fedriani, J.M., P. Rey, J.L. Garrido, J. Guitian, C.M. Herrera, M. Mendrano, A. Sanchez-Lafuente, and
X. Cerdá. 2004. Geographical variation in the potential of mice to constrain an ant-seed disper-
sal mutualism. Oikos 105: 181–91.
Fenner, M. and K. Thompson. 2005. The Ecology of Seeds, 2nd edn. Cambridge University Press,
Cambridge, UK.
Ferris, R. and J.W. Humohreym. 1999. A review of potential biodiversity indicators for application in
British forests. Forestry 72 (4): 313–28.
Finkeldey, R. and M. Ziehe. 2004. Genetic implications of silvicultural regimes. Forest Ecology and
Management 197: 231–44.
Finzi, A.C. and C.D. Canham. 2000. Sapling growth in response to light and nitrogen availability in a
southern New England forest. Forest Ecology and Management 131: 153–65.
Fischer, H., O. Bens, and R. Hüttl. 2002. Changes in humus form, humus stock and soil organic mat-
ter distribution caused by forest transformation in the north eastern lowlands of Germany.
Forstwissenschaftliches Centralblatt 121: 322–34.
Fischer, A. and H. Fischer. 2012. Restoration of temperate forests: A European approach. In: van
Andel, J. and J. Aronson (eds.), Restoration Ecology: The New Frontier, 2nd ed. Vol. 12. Blackwell
Publishing Ltd., Chichester, UK, pp. 145–160.
Fischer, H. and S. Wagner. 2009. Silvicultural responses to predicted climate change scenarios.
Westnik—Journal of Forest Ecology and Forest Management, Mari El. 2: 12–23.
Flaig, H. and H. Mohr. 1990. Auswirkungen eines erhöhten Ammoniumangebots auf die
Keimpanzen der gemeinen Kiefer (Pinus sylvestris L.). Allgemeine Forst Jagdzeitung 162: 35–42.
Forester, J.D., D.P. Anderson, and M.G. Turner. 2007. Do high-density patches of coarse wood
and regenerating saplings create browsing refugia for aspen (Populus tremuloides Michx.) in
Yellowstone National Park (USA)? Forest Ecology and Management 253 (1–3): 211–19.
Forget, P.M., J.E. Lambert, P.E. Hulme and S.B. Vander Wall (eds.) 2005. Seed Fate: Predation, Dispersal
and Seedling Establishment. CAB International, Wallingford, UK.
Foster, J.R. and W.A. Reiners. 1986. Size distribution and expansion of canopy gaps in a northern
Appalachian spruce-r forest. Vegetatio 68: 109–14.
Fotelli, M.N., A. Gessler, A.D. Peuke, and H. Rennenberg. 2001. Drought affects the competitive inter-
actions between Fagus sylvatica seedlings and an early successional species, Rubus fruticosus:
Responses of growth, water status and delta13C composition. New Phytologist 151 (2): 427–35.
Fox, J.W. 2013. The intermediate disturbance hypothesis should be abandoned. Trends in Ecology and
Evolution (Amst.) 28 (2): 86–92.
Franklin, J.F., H.H. Shugart, and M.E. Harmon. 1987. Tree death as an ecological process. Bioscience
37 (8): 550–6.
Fredericksen, T.S., B. Ross, W. Hoffmann, M. Lester, J. Beyea, M.L. Morrison, and B.N. Johnson. 1998.
Adequacy of natural hardwood regeneration on forestlands in northeastern Pennsylvania.
Northern Journal of Applied Forestry 15: 130–34.
Freestone, A.L. 2006. Facilitation drives local abundance and regional distribution of rare plant in a
harsh environment. Ecology 87 (11): 2728–35.
Frelich, L.E. 2002. Forest Dynamics and Disturbance Regimes. Cambridge University Press, Cambridge.
Fries, C., O. Johansson, B. Petterson, and P. Simonsson. 1997. Silvicultural models to maintain and
restore natural stand structures in Swedish boreal forests. Forest Ecology and Management 94:
89–103.
Galatowitsch, S.M. 2012. Ecological restoration. Sinauer Associates, Sunderland, Massachusetts, USA.
Gaudio, N., P. Balandier, and A. Marquier. 2008. Light-dependent development of two competitive
species (Rubus idaeus, Cytisus scoparius) colonizing gaps in temperate forest. Annales of Forest
Science 65(1): 104.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
149Developing Restoration Strategies for Temperate Forests
Gayer, K. 1886. The Mixed Forest. Parey Verlag, Berlin.
Geburek Th. and J. Turok. 2005. Conservation and Management of Forest Genetic Resources in Europe.
Arbora Publishers, Zvolen, Slovakia, 693p.
George, L.O. and F.A. Bazzaz. 1999. The fern understory as an ecological lter: Emergence and estab-
lishment of canopy-tree seedlings. Ecology 80: 833–45.
Gholz, H.L. and L. Boring. 1991. Characterizing the site: Environment, associated vegetation and site
potential. In: Duryea, M.L. and P. Daugherty (eds.), Regeneration Manual for the Southern Pines.
Springer, New York, pp. 163–82.
Gilbert, B. and M.J. Lechowicz. 2004. Neutrality, niches, and dispersal in a temperate forest under-
story. Proceedings of the National Academy Sciences U.S.A. 101 (20): 7651–56.
Gillam, F.S. 2007. The ecological signicance of the herbaceous layer in temperate forest ecosystems.
BioScience 57 (10): 845.
Gilliam, F.S. and M.R. Roberts. 2003. The Herbaceous Layer in Forests of Eastern North America. Oxford
University Press, New York.
González-Rodríguez, V. and R. Villar. 2012. Post-dispersal seed removal in four Mediterranean oaks:
Species and microhabitat selection differ depending on large herbivore activity. Ecological
Research 27 (3): 587–94.
González-Varo, J.P., J.V. López-Bao, and J. Guitián. 2013. Functional diversity among seed dispersal
kernels generated by carnivorous mammals. Journal of Animal Ecology 82: 562–71.
Goldammer, J.G. 2013. Prescribed Burning in Russia and Neighbouring Temperate-Boreal Eurasia. Kesssel
Publishing House, Remagen-Oberwinter.
Goldberg, D.E. 1990. Components of resource competition in plant communities. In: Grace, J.B., and
D. Tilman (eds.), Perspectives of Plant Competition. Academic Press, New York, NY, pp. 27–49.
Goldberg, D.E. and K. Landa. 1991. Competitive effect and response: Hierarchies and correlated
traits in the early stages of competition. Journal of Ecology 79 (4): 1013–1030.
Gómez, J.M., D. García, and R. Zamora. 2003. Impact of vertebrate acorn- and seedling-predators on
a Mediterranean Quercus pyrenaica forest. Forest Ecology and Management 180: 125–34.
Goodall-Copestake, W., M.L. Hollingsworth, P.M. Hollingsworth, G. Jenkins, and E. Collin. 2005.
Molecular markers and ex situ conservation of the European elms (Ulmus spp.). Biological
Conservation 122: 537–46.
Gordon, A.M., J.A. Simpson, and P.A. Williams. 1995. Six-year response of red oak seedlings planted
under a shelterwood in central Ontario. Canadian Journal of Forest Research 25: 603–13.
Goulet, F. 1995. Frost heaving of forest tree seedlings: A review. New Forests 9 (1): 67–94.
Gracia, M., F. Montané, J. Piqué, and J. Retana. 2007. Overstory structure and topographic gradients
determining diversity and abundance of understory shrub species in temperate forests in cen-
tral Pyrenees (NE Spain). Forest Ecology and Management 242 (2–3): 391–97.
Grassi, G. and R. Giannini. 2005. Inuence of light and competition on crown and shoot morpho-
logical parameters of Norway spruce and silver r saplings. Annales of Forest Science 62 (3):
269–74.
Gray, A.N., T.A. Spies, and M.J. Easter. 2002. Microclimatic and soil moisture responses to gap forma-
tion in coastal Douglas-r forests. Canadian Journal of Forest Research 32 (2): 332–43.
Greene, D.F. and E.A. Johnson. 1996. Wind dispersal of seeds from a forest into a clearing. Ecology
77: 595–609.
Grime, J.P. 1979. Plant Strategies and Vegetation Processes. John Wiley & Sons, Bath.
Grisez, T.J. 1960. Slash helps protect seedlings from deer browsing. Journal of Forestry 58: 385–87.
Groot, A. 1999. Effects of shelter and competition on the early growth of planted white spruce (Picea
glauca). Canadian Journal of Forest Research 29: 1002–14.
Grubb, P.J. 1977. The maintenance of species-richness in plant communities: The importance of the
regeneration niche. Biological Review 52 (1): 107–45.
Guitián, J. and I. Munilla. 2010. Responses of mammal dispersers to fruit availability: Rowan (Sorbus
aucuparia) and carnivores in mountain habitats of northern Spain. Acta Oecologica 36 (2): 242.
Guo, L., J. Chen, X. Cui, B. Fan, and H. Lin. 2013. Application of ground penetrating radar for coarse
root detection and quantication: A review. Plant Soil 362: 1–23.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
150 Restoration of Boreal and Temperate Forests
Gustafsson, L., L. Kouki, and A. Sverdrup-Thygeson. 2010. Tree retention as a conservation mea-
sure in clear-cut forests of northern Europe: A review of ecological consequences. Scandinavian
Journal of Forest Research 25: 295–308.
Hagemann, U., G. van der Kelen, and S. Wagner. 2013. Comparative assessment of natural regenera-
tion quality in two northern hardwood stands. Northern Journal of Applied Forestry 30 (1): 5–15.
Hagemann, U., M. Moroni, and F. Makeschin. 2009. Deadwood abundance in Labrador high-boreal
black spruce forests. Canadian Journal of Forest Research 39 (1): 131–42.
Hahn, K. and R.P. Thomsen. 2007. Ground ora in Suserup Skov: Characterized by forest continuity
and natural gap dynamics or edge-effect and introduced species? Ecological Bulletins 52: 167–81.
Halpern, C.H.B., S.A. Evans, C.R. Nelson, D. McKenzie, D.A. Liguori, D.E. Hibbs, and M.G. Halaj.
1999. Response of forest vegetation to varying levels and patterns of green-tree retention: An
overview of a long-term experiment. Northwest Science (Special Issue) 73: 27–44.
Hamm, T., J. Weidig, F. Huth, W. Kulisch, and S. Wagner. 2014. Wachstumsreaktionen junger
weißtannen-voraussaaten auf begleitvegetation und strahlungskonkurrenz. Allgemeine Forst-
und Jagdzeitung 185 (3/4): 45–59.
Härdtle, W., T. Aßmann, R. Diggelen, and G. Oheimb. 2009. Renaturierung und management von
heiden. In: S. Zerbe and G. Wiegleb (eds.), Renaturierung von Ökosystemen in Mitteleuropa,
Spektrum Akademischer Verlag, Heidelberg, pp. 317–47.
Härdtle, W., G. von Oheimb, and C. Westphal. 2003. The effects of light and soil conditions on the spe-
cies richness of the ground vegetation of deciduous forests in northern Germany (Schleswig-
Holstein). Forest Ecology and Management 182 (1–3): 327–38.
Harmer, R., A. Kiewitt, and G. Morgan. 2012. Can overstorey retention be used to control bramble
(Rubus fruticosus L. agg.) during regeneration of forests? Forestry 85: 135–44.
Harmon, M.E. 1989a. Effects of bark fragmentation on plant succession on conifer logs in the Picea-
Tsuga forests of Olympic National Park. The American Midland Naturalist 121 (1): 112–24.
Harmon, M.E. 1989b. Retention of needles and seeds on logs in Picea sitchensis—Tsuga heterophylla
forests of coastal Oregon and Washington. Canadian Journal of Botany 67 (6): 1833–37.
Harmon, M.E. and J.F. Franklin. 1989. Tree seedlings on logs in Picea-Tsuga forests of Oregon and
Washington. Ecology 70 (1): 48.
Harmon, M.E., J.F. Franklin, J.F. Swanson, P. Sollins, S.V. Gregory, J.D. Lattin, N.H. Anderson etal.
2004. Ecology of woody debris in temperate ecosystems. Advances in Ecological Research Classic
Papers 34: 59–234.
Harper, J.L. 1977. Population Biology of Plants. Academic Press, London.
Hartshorn, G.S. 1989. Application of gap theory to tropical forest management: Natural regeneration
on strip clear-cuts in the Peruvian Amazon. Ecology 70 (567–9).
Hattemer, H.H. 2005. Phenotypic and genetic variation. In: Geburek, T., Turok, J. (ed.), Conservation and
Management of Forest Genetic Resources in Europe. Arbora Publishers, Zvolen, Slovakia, pp. 129–48.
Havranek, W.M. and V. Benecke. 1978. The inuence of soil moisture on water potential, transpira-
tion and photosynthesis of conifer seedlings. Plant and Soil 49: 91–103.
Haywood, J.D. 2000. Mulch and hexazinone herbicide shorten the time longleaf pine seedlings are in
the grass stage and increase height growth. New Forests 19 (3): 279–90.
Hermy, M., O. Honnay, L. Firbank, C. Grashof-Bokdam, and J.E. Lawesson. 1999. An ecological com-
parison between ancient and other forest plant species of Europe, and the implications for for-
est conservation. Biological Conservation 91 (1): 9–22.
Hertel, O., C.A. Skjøth, S. Reis, A. Bleeker, R.M. Harrison, J.N. Cape, D. Fowler etal. 2012. Governing
processes for reactive nitrogen compounds in the European atmosphere, Biogeosciences, 9: 4921–54.
Hietala, A.M., L. Mehli, N.E. Nagy, H. Kvaalen, and N. La Porta. 2005. Rhizoctonia solani AG 2-1 as
a causative agent of cotyledon rot on European beech (Fagus sylvatica). Forest Pathology 35 (6):
397–410.
Hill, J.K., K.C. Hamer, J. Tangah, and M. Dawood. 2001. Ecology of tropical butteries in rainforest
gaps. Oecologia 128 (2): 294–302.
Hille, M. and J. den Ouden. 2005. Fuel load, humus consumption and humus moisture dynamics in
Central European Scots pine stands. International Journal of Wildland Fire 14: 153–59.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
151Developing Restoration Strategies for Temperate Forests
Hille, M. and J. Ouden. 2004. Improved recruitment and early growth of Scots pine (Pinus sylvestrisL.)
seedlings after re and soil scarication. European Journal of Forest Research 123 (3): 213–18.
Hilton G, J. Packham. 2003. Variation in the masting of common beech (Fagus sylvatica L.) in northern
Europe over two centuries (1800–2001). Forestry 76: 319–28.
Hodge, S.J. and G.F. Peterken. 1998. Deadwood in British forests: Priorities and a strategy. Forestry
71 (2): 99–112.
Hofgaard, A. 1993. Structure and regeneration patterns in a virgin Picea abies forest in northern
Sweden. Journal of Vegetation Science 4 (5): 601–08.
Holl, K.D. and T.M. Aide. 2011. When and where to actively restore ecosystems? Forest Ecology and
Management 261: 1558–63.
Holmsgaard, E. and H.C. Olsen. 1966. Experimental induction of owering in beech. Forstliches
Forsogsraes. Danemark 30: 3–17.
Honnay, O., B. Bossuyt, K. Verheyen, J. Butaye, H. Jacquemyn, and M. Hermy. 2002. Ecological per-
spectives for the restoration of plant communities in European temperate forests. Biodiversity
and Conservation 11: 213–42.
Hosius, B., L. Leinemann, M. Konnert, and F. Bergman. 2006. Genetic aspects of forestry in the Central
Europe. European Journal of Forest Research 125: 407–17.
Hulme, P.E. and T. Borelli. 1999. Variability in post-dispersal predation in deciduous woodland:
Relative importance of location, seed species, burial and density. Plant Ecology 145: 149–56.
Hulme, P.E. and M.K. Hunt. 1999. Rodent post-dispersal seed predation in deciduous woodland:
Predator response to absolute and relative abundance of prey. Journal of Animal Ecology 68: 417–28.
Hüning, Chr., S. Tischew, and G. Karste. 2008. Erfolgskontrolle der renaturierungsmaßnahmen auf
der brockenkuppe im Nationalpark Harz. Hercynia N.F 41: 201–17.
Hunter, M.L. 1999. Maintaining Biodiversity in Forest Ecosystems. Cambridge University Press,
Cambridge, UK, New York, NY, USA.
Hunter, A.F. and L.W. Aarssen. 1988. Plants helping plants: New evidence indicates that benecence
is important in vegetation. BioScience 38 (1): 34–40.
Huss, J. and A. Stephani. 1978. Lassen sich angekommene buchennaturverjüngungen durch früh-
zeitige auichtung, durch düngung oder unkrautbekämpfung rascher aus der gefahrenzone
bringen? Allgemeine Forst- und Jagdzeitung 149 (8): 133–45.
Hutchinson, G.E. 1978. An Introduction to Population Ecology. Yale University Press, New Haven.
Huth, F. 2009. Untersuchungen zur verjüngungsökologie der sand-birke (Betula pendula Roth). phd.
Technische Universität Dresden, Fakultät Forst-, Geo- und Hydrowissenschaften, 383p.
Huth, F. and S. Wagner. 2006. Gap structure and establishment of Silver birch regeneration (Betula
pendula Roth.) in Norway spruce stands (Picea abies L. Karst.). Forest Ecology and Management
229 (1–3): 314–24.
Huth, F. and S. Wagner. 2013. Ecosystem services and continuous cover forests—A silvicultural anal-
ysis. Schweizerische Zeitschrift für Forstwesen 164 (2): 27–36.
Hüttl, R.F. and A.D. Bradshaw. 2001. Ecology of postmining landscapes. Ecological Engineering Special
Issue 17 (2–3).
Hüttl, R.F.J. and E. Weber. 2001. Forest ecosystem development in post-mining landscapes: A case
study of the Lusatian lignite district. Naturwissenschaften 88: 322–29.
Hynynen, J., P. Niemistö, A. Vihera-Aarnio, A. Brunner, S. Hein, and P. Velling. 2010. Silviculture of
birch (Betula pendula Roth and Betula pubescens Ehrh.) in northern Europe. Forestry 83: 103–19.
Iijima, H. and M. Shibuya. 2010. Evaluation of suitable conditions for natural regeneration of Picea
jezoensis on fallen logs. Journal of Forest Research 15 (1): 46–54.
Iijima, H., M. Shibuya, and H. Saito. 2007. Effects of surface and light conditions of fallen logs on the emer-
gence and survival of coniferous seedlings and saplings. Journal of Forest Research 12 (4): 262–69.
Janos, D.P. 1992. Heterogeneity and scale in tropical vesicular-arbuscular mycorrhiza formation. In:
Read, D.J., D.H. Lewis, A.H. Fitter, and I.J. Alexander (eds.), Mycorrhizas in Ecosystems. CAB,
Wallingford, pp. 276–82.
Jansen, P.A., F. Bongers, and L. Hemerik, L. 2004. Seed mass and mast seeding enhance dispersal by
a neotropical scatter-hoarding rodent. Ecological Monographs 74: 569–89.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
152 Restoration of Boreal and Temperate Forests
Janzen, D.H. 1970. Herbivores and the number of tree species in tropical forests. The American
Naturalist 104: 501–28.
Jensen, T.S. 1985. Seed-seed predator interactions of European beech (Fagus sylvatica) and forest
rodents (Clethrionomys glareolus and Apodemus avicollis). Oikos 44: 149–56.
Jensen, A.M., M. Löf, and E.S. Gardiner. 2011. Effects of above- and below-ground competition from
shrubs on photosynthesis, transpiration and growth in Quercus robur L. seedlings. Environmental
and Experimental Botany 71 (3): 367–75.
Ježek, K. 2004. Contribution of regeneration on dead wood to the spontaneous regeneration of a
mountain forest. Journal of Forest Science 50: 405–14.
Jobidon, R. 1994. Light threshold for optimal black spruce (Picea mariana) seedling growth and devel-
opment under brush competition. Canadian Journal of Forest Research 24: 1629–35.
Johansson, K., O. Langvall, and J. Bergh. 2012. Optimization of environmental factors affecting initial
growth of Norway spruce seedlings. Silva Fennica 46 (1): 27–38.
Jonášová, M. and K. Prach. 2004. Central-European mountain spruce (Picea abies (L.) Karst.) forests:
Regeneration of tree species after a bark beetle outbreak. Ecological Engineering 23 (1): 15–27.
Jonášová, M., E. Vávrová, and P. Cudlín. 2010. Western Carpathian mountain spruce forest after a
windthrow: Natural regeneration in cleared and uncleared areas. Forest Ecology and Management
259 (6): 1127–34.
Jonsson, B.G., N. Kruys, and T. Ranius. 2005. Ecology of species living on dead wood—Lessons for
dead wood management. Silva Fennica 39 (2): 289–309.
Josa, R., M. Jorba, and V. Ramon. 2012. Opencast mine restoration in a Mediterranean semi-arid envi-
ronment: Failure of some common practices. Ecological Engineering 42: 183–91.
Jump, A. and J. Penuelas. 2007. Extensive spatial genetic structure revealed by AFLP but not SSR
molecular markers in the wind-pollinated tree, Fagus sylvatica. Molecular Ecology 16: 925–36.
Kahl, T., M. Mund, J. Bauhus, and E.-D. Schulze. 2012. Dissolved organic carbon from European
beech logs: Patterns of input to and retention by surface soil. Ecoscience 19 (4): 364–73.
Karlsson, C. 2000. Seed production of Pinus sylvestris after release cutting. Canadian Journal of Forest
Research 30: 982–9.
Karlsson, M. 2001. Doctoral diss. Vol. 196. Southern Swedish Forest Research Centre, SLU. Acta
Universitatis agriculturae Sueciae, Silvestria. Natural Regeneration of Broadleaved Tree Species
in Southern Sweden; p. 1–44.
Kauppi, S., M. Romantschuk, R. Strömmer, and A. Sinkkonen. 2012. Natural attenuation is enhanced
in previously contaminated and coniferous forest soils. Environmental Science and Pollution
Research 19 (1): 53–63.
Keidel, S., P. Meyer, and N. Bartsch. 2008. Regeneration eines naturnahen Fichtenwaldökosystems im
Harz nach großächiger Störung. Forstarchiv 79: 187–96.
Kelly, D. and V.L. Sork. 2002. Mast seeding in perennial plants: Why, how, where? Annual Review
Ecology Systematics 33: 427–47.
Kerr, G. 1999. The use of silvicultural systems to enhance the biological diversity of plantation forests
in Britain. Forestry 72: 191–205.
Kimmins, J.P. 1987. Forest Ecology. Macmillan Publishing Company, New York, 531 pp.
Kitajima, K. and J.A. Myers. 2008. Seedling ecophysiology: Strategies towards achievement of posi-
tive carbon balance. In: Leck, M.A., V.T. Parker, and R.L. Simpson (eds.), Seedling Ecology and
Evolution. Cambridge University Press, Cambridge, UK, pp. 172–188.
Kliejunas, J.T., W.J. Otrosina, and J.R. Allison. 2005. Uprooting and trenching to control annosus root
disease in a developed recreation site: 12-year results. Western Journal of Applied Forestry 20 (3):
154–9.
Klimešova, J. and L. Klimeš. 2007. Bud banks and their role in vegetative regeneration—A litera-
ture review and proposal for simple classication and assessment. Perspectives in Plant Ecology,
Evolution and Systematics 8 (3): 115–29.
Knapp, A.K. and W.K. Smith. 1982. Factors inuencing understory seedling establishment of
Engelmann spruce (Picea engelmannii) and subalpine r (Abies lasiocarpa) in southeast Wyoming.
Canadian Journal of Botany 60 (12): 2753–61.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
153Developing Restoration Strategies for Temperate Forests
Knudsen, I.M.B., K.A. Thomsen, B. Jensen, and K.M. Poulsen. 2004. Effects of hot water treatment,
biocontrol agents, disinfectants and a fungicide on storability of English oak acorns and control
of the pathogen, Ciboria batschiana. Forest Pathology 34: 47–64.
Kohyama, T. 1987. Stand dynamics in a primary warm temperate rain forest analyzed by the diffu-
sion equation. Botanical Magazine, Tokyo 100, 305–317.
Koizumi, A., N. Oonuma, Y. Sasaki, and K. Takahashi. 2007. Difference in uprooting resistance among
coniferous species planted in soils of volcanic origin. Journal of Forest Research 12: 237–242.
Koop, H. 1987. Vegetative reproduction of trees in some European natural forests. Vegetatio 72 (2):
103–10.
Korb, J.E., J.D. Springer, S.R. Powers, and M.M. Moore. 2005. Soil seed banks in Pinus ponderosa for-
ests in Arizona: Clues to site history and restoration potential. Applied Vegetation Science 8 (1):
103–12.
Korpel, S. 1995. Old growth Forests of the West Carpathians. Gustav Fischer, Stuttgart, Jena, New York.
Kozlov, M.V., E. Haukioja, A.V. Bakhtiarov, D.N. Stroganov, and S.N. Zimina. 2000. Root versus can-
opy uptake of heavy metals by birch in an industrially polluted area: Contrasting behaviour of
nickel and copper. Environmental Pollution 107 (3): 413–20.
Kozlowski, T.T. (ed.), 1974. Fire and Ecosystems: Physiological Ecology. Academic Press, New York.
Král, K., J. Trochta, and T. Vrška. 2012. Can re and secondary succession assist in the regeneration
of forests in a national park? In: Jongepierová, I., P. Pešout, J.W. Jongepier, and K. Prach (eds.),
Ecological Restoration in the Czech Republic, Nature Conservation Agency of the Czech Republic,
Prague, pp. 24–26.
Krautzer, B. and B. Klug. 2009. Renaturierung von subalpinen und alpinen Ökosystemen (Restoration
of subalpine and alpine ecosystems). In: Zerbe, S. and G. Wiegleb, (eds.), Renaturierung
von Ökosystemen in Mitteleuropa (Restoration of Ecosystems in Central Europe). Spektrum
Akademischer Verlag, Heidelberg, pp. 209–34.
Kubin, E. and L. Kemppainen. 1994. Effect of soil preparation of boreal spruce forest on air and soil
temperature conditions in forest regeneration areas. Acta Forestalia Fennica 244: 1–56.
Kuiters, A.T., G.M.J. Mohren, and S.E. Van Wieren. 1996. Ungulates in temperate forest ecosystems.
Forest Ecology and Management 88: 1–5.
Kupferschmid, A.D., P. Brang, W. Schönenberger, and H. Bugmann. 2006. Predicting tree regenera-
tion in Picea abies snag stands. European Journal of Forest Research 125: 163–179.
Kupferschmid, A.D. and H. Bugmann. 2005. Effect of microsites, logs and ungulate browsing on
Picea abies regeneration in a mountain forest. Forest Ecology and Management 205 (1–3): 251–65.
Küßner, R., P. Reynolds, and F.W. Bell 2000. Growth response of Picea mariana seedlings to competi-
tion for radiation. Scandinavian Journal of Forest Research 15 (3): 334–342.
Kutscher, M., M. Bachmann, and A. Göttlein. 2009. Renaissance der Saat im Alpenraum? (Renaissance
of sowing in the Alps)? Waldbau—Planung, Pege, Perspektiven, LWF aktuell 68.
Kuuluvainen, T. and R. Kalmari. 2003. Regeneration microsites of Picea abies seedlings in a windthrow
area of a boreal old-growth forest in southern Finland. Annales Botanici Fennici 40 (6): 401–13.
Kuuluvainen, T. and T. Pukkala. 1989. Effect of Scots pine seed trees on the density of ground vegeta-
tion and tree seedlings. Silva Fennica 23 (2): 159–67.
Lack, A.J. 1991. Dead logs as a substrate for rain forest trees in Dominica. Journal of Tropical Ecology
7 (03): 401.
LaMontagne, J.M. and S. Boutin. 2009. Quantitative methods for dening mast-seeding years across
species and studies. Journal of Vegetation Science 20: 745–53.
LaPaix, R., B. Freedman, and D. Patriquin. 2009. Ground vegetation as an indicator of ecological
integrity. Environmental Review 17: 249–65.
Lässig, R., S. Egli, O. Odermatt, W. Schönenberger, B. Stöckli, and T. Wohlgemuth. 1995. Beginn
der Wiederbewaldung auf Windwurfächen (Reforestation by natural regeneration after
Windthrow). Schweizerische Zeitschrift für Forstwesen 146 (11): 893–911.
Lässig, R. and S.A. Mocalov. 2000. Frequency and characteristics of severe storms in the Urals and
their inuence on the development, structure and management of the boreal forests. Forest
Ecology and Management 135, 1–3: 179–94.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
154 Restoration of Boreal and Temperate Forests
Lautenschlager, R.A. 1995. Competition between forest brush and planted white spruce in north-
central Maine. Northern Journal of Applied Forestry 12: 163–7.
Lautenschlager, R.A. 1999. Environmental resources interactions affect raspberry growth and its
competition with white spruce. Canadian Journal of Forest Research 29: 906–16.
Leck, M.A., V.T. Parker, and R. Simpson. 2008. Seedling Ecology and Evolution. Cambridge University
Press, Cambridge.
Leder, B., S. Wagner, J. Wollmerstadt, and C. Ammer. 2003. Bucheckern-Voraussaat unter
Fichtenschirm—Ergebnisse eines Versuchs des Deutschen Verbandes Forstlicher Forschung-
sanstalten/Sektion Waldbau. Direct Seeding of European Beech (Fagus sylvatica L.) in Pure
Norway Spruce Stands (Picea abies [L.] Karst.)—Results of an Experiment by the German Union
of Forest Research Organizations/Silviculture Division. Forstwissenschaiches Centralblatt 122
(3): 160–74.
Lefèvre, F., 2004. Human impacts on forest genetic resources in the temperate zone: An updated
review. Forest Ecology and Management 197: 257–71.
Leibundgut, H. 1982. European Old-Growth Forests. P. Haupt, Bern, Stuttgart.
Leibundgut, H. 1984. Die natürliche Waldverjüngung. 2. überabeitete und erw. Au. Bern: P. Haupt.
Leishman, M.R. and M. Westoby. 1994. The role of large seeds in seedling establishment in dry soil
conditions—Experimental evidence from semi-arid species. Journal of Ecology 82: 249–258.
LePage, P.T., C.D. Canham, K.D. Coates, and P. Bartemucci. 2000. Seed abundance versus substrate
limitation of seedling recruitment in northern temperate forests of British Columbia. Canadian
Journal of Forest Research 30: 415–27.
Leuschner, C. 1994. Walddynamik auf Sandböden in der Lüneburger Heide (NW-Deutschland).
Phytocoenologia 22: 289–324.
Levey, D.J. 1988. Tropical wet forest treefall gaps and distributions of understory birds and plants.
Ecology 69: 1076–89.
Leyer, I., E. Mosner, and B. Lehmann. 2012. Managing oodplain-forest restoration in European
river landscapes combining ecological and ood-protection issues. Ecological Applications 22
(1): 240–49.
Li, H.J. and Z.B. Zhang. 2007. Effects of mast seeding and rodent abundance on seed predation and
dispersal by rodents in Prunus armeniaca (Rosaceae). Forest Ecology and Management 242: 511–7.
Lindenmayer, D., E. Knight, L. McBurney, D. Michael, and S.C. Banks. 2010. Small mammals and
retention islands: An experimental study of animal response to alternative logging practices.
Forest Ecology and Management 260: 2070–78.
Lindenmayer, D. and J.F. Franklin. 2002. Conserving Forest Biodiversity: A Comprehensive Multiscaled
Approach. Island Press, Washington.
Lindenmayer, D.B., J.F. Franklin, A. Lõhmus, S.C. Baker, J. Bauhus, W. Beese, A. Brodie etal. 2012.
Amajor shift to the retention approach for forestry can help resolve some global forest sustain-
ability issues. Conservation Letters 5 (6): 421–31.
Löf, M. 2000. Establishment and growth in seedlings of Fagus sylvatica and Quercus robur: Inuence of
interference from herbaceous vegetation. Canadian Journal of Forest Research 30: 855–64.
Löf, M., A. Thomsen, and P. Madsen. 2004. Sowing and transplanting of broadleaves (Fagus sylvatica
L., Quercus robur L., Prunus avium L. and Crataegus monogyna Jacq.) for afforestation of farm-
land. Forest Ecology and Management 188 (1–3): 113–23.
Löf, M., D.C. Dey, R.M. Navarro, and D.F. Jacobs. 2012. Mechanical site preparation for forest restora-
tion. New Forests 48: 825–48.
Löf, M., D. Rydberg, and A. Bolte. 2006. Mounding site preparation for forest restoration: Survival
and short term growth response in Quercus robur L. seedlings. Forest Ecology and Management
232 (1–3): 19–25.
Löf, M. and N.T. Welander. 2004. Inuence of herbaceous competitors on early growth in direct
seeded Fagus sylvatica L. and Quercus robur L. Annales of Forest Science 61: 781–8.
Lorimer, C.G. 1989. Relative effects of small and large disturbances on temperate hardwood forest
structure. Ecology 70 (3): 565.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
155Developing Restoration Strategies for Temperate Forests
Lorimer, C.G., J.W. Chapman, and W.D. Lambert. 1994. Tall understorey vegetation as a factor in the
poor development of oak seedlings beneath mature stands. Ecology 82 (2): 227–37.
Lundqvist, L. 1995. Simulation of sapling population dynamics in uneven-aged Picea abies forests.
Annals of Botany 76, 371–80.
Luoma, D.L., C.A. Stockdale, R. Molina, and J.L. Eberhart. 2006. The spatial inuence of Pseudotsuga
menziesii retention trees on ectomycorrhiza diversity. Canadian Journal of Forest Research 36 (10):
2561–73.
Madsen, P. 1995. Effects of soil water content, fertilization, light, weed competition and seed bed type
on natural regeneration of beech (Fagus sylvatica). Forest Ecology and Management 72: 251–64.
Malanson, G.P. and M.P. Armstrong. 1996. Dispersal probability and forest diversity in a fragmented
landscape. Ecological Modelling 87: 91–102.
Mallik, A.U. and C.H. Gimingham. 1985. Ecological effects of heather burning II. Effects on seed
germination and vegetative regeneration. Journal of Ecology 73 (2): 633–44.
Mallik, A.U. and F. Pellissier. 2000. Effects of Vaccinium myrtillus on spruce regeneration: Testing the
notion of coevolutionary signicance of allelopathy. Journal of Chemical Ecology 26: 2197–209.
Mallik, A.U., F.W. Bell, and Y. Gong. 1997. Regeneration behavior of competing plants after clear
cutting: Implications for vegetation management. Forest Ecology and Management 95 (1): 1–10.
Manso, R., M. Fortin, R. Calama, and M. Pardos. 2013. Modelling seed germination in forest tree
species through survival analysis. The Pinus pinea L. case study. Forest Ecology and Management
289: 9–21.
Matveinen-Huju, K., J. Niemelä, H. Rita, and R.B. O’Hara. 2006. Retention-tree groups in clear-cuts:
Do they constitute ‘life-boats’ for spiders and carabids? Forest Ecology and Management 230 (1–3):
119–35.
McComb, B.C. 2007. Wildlife Habitat Management: Concepts and Applications in Forestry. Boca Raton,
New York: CRC Press/Taylor & Francis Group.
McGee, G.G. and J.P. Birmingham. 1997. Decaying logs as germination sites in northern hardwood
forests. Forest Ecology and Management 14 (4): 178–82.
McWilliams, W.H., S.L. Stout, T.W. Bowersox, and L.H. McCormick. 1995. Adequacy of advance tree-
seedling regeneration in Pennsylvania’s forests. Northern Journal of Applied Forestry 12 (4): 187–91.
Meinen, C., D. Hertel, and C. Leuschner. 2009. Biomass and morphology of ne roots in temper-
ate broad-leaved forests differing in tree species diversity: Is there evidence of below-ground
overyielding? Oecologia 161 (1): 99–111.
Messier, C.C., K.J. Puettmann, and K.D. Coates. 2013. Managing Forests as Complex Adaptive Systems:
Building Resilience to the Challenge of Global Change. The Earthscan forest library. Routledge
Taylor & Francis Group, London and New York.
Metlen, K.L. and C.E. Fiedler. 2006. Restoration treatment effects on the understory of ponderosa pine/
Douglas-r forests in western Montana, USA. Forest Ecology and Management 222 (1–3): 355–69.
Meyer, P. and M. Schmidt. 2011. Accumulation of dead wood in abandoned beech (Fagus sylvatica L.)
forests in northwestern Germany. Forest Ecology and Management 261 (3): 342–52.
Millar, C.I., N.L. Stephenson, and S.L. Stephens. 2007. Climate change and forests of the future:
Managing in the face of uncertainty. Ecological Applications 17 (8): 2145–51.
Millerón, M., U. Lopez de Heredia, Z. Lorenzo, J. Alonso, and A. Dounavi. 2013. Assessment of spa-
tial discordance of primary and effective seed dispersal of European beech (Fagus sylvatica L.)
by ecological and genetic methods. Molecular Ecology 22: 1531–45.
Mitchell, S.J. 2013. Wind as a natural disturbance agent in forests: A synthesis (Review). Forestry
86 (2): 147–57.
Mitchell, R.J., J.F. Franklin, B.J. Palik, K.K. Kirkman, L.L. Smith, R.T. Engstrom, and M.L. Hunter, Jr.
2004. Natural disturbance-based silviculture for restoration and maintenance of biological diversity.
Final Report to the National Commission on Science for Sustainable Forestry.
Mitchell, A.K., R. Koppenaal, G. Goodmanson, R. Benton, and T. Bown. 2007. Regenerating montane
conifers with variable retention systems in a coastal British Columbia forest: 10-Year results.
Forest Ecology and Management 246 (2–3): 240–50.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
156 Restoration of Boreal and Temperate Forests
Modry, M., D. Hubeny, and K. Rejsek. 2004. Differential response of naturally regenerated European
shade tolerant tree species to soil type and light availability. Forest Ecology and Management 188:
185–95.
Mölder, A., M. Bernhardt-Römermann, and W. Schmidt. 2008. Herb-layer diversity in deciduous for-
ests: Raised by tree richness or beaten by beech? Forest Ecology and Management 256 (3): 272–81.
Moncur, M.W. and O. Hasan. 1994. Floral induction in Eucalyptus nitens. Tree Physiology 14: 1303–12.
Morris, L.A., S.A. Moss, and W.S. Garbett. 1993. Competitive interference between selected herba-
ceous and woody plants and Pinus taeda L. during two growing season following planting.
Forest Science 39: 166–87.
Mortzfeldt, U. 1896. Über horstweisen Vorverjüngungsbetrieb. Zeitschrift für Forst- und Jagdwesen
28: 2–31.
Mosandl, R. and A. Kleinert. 1998. Development of oaks (Quercus petraea (Matt.) Liebl.) emerged
from bird-dispersed seeds under old-growth pine (Pinus silvestris L.) stands. Forest Ecology and
Management 106: 35–44.
Motta, R., R. Berretti, E. Lingua, and P. Piussi. 2006. Coarse woody debris, forest structure and regen-
eration in the Valbona Forest Reserve, Paneveggio, Italian Alps. Forest Ecology and Management
235 (1–3): 155–63.
Mountford, E.P. 2001. Natural Canopy Gap Characteristics in European Beech Forests. Nat-Man
Project Report.
Mueller-Dombois, D. and H. Ellenberg. 1974. Aims and Methods of Vegetation Ecology. Wiley and Sons,
New York, 547p.
Müller, J. and R. Bütler. 2010. A review of habitat thresholds for dead wood: A baseline for manage-
ment recommendations in European forests. European Journal of Forest Research 129 (6): 981–92.
Müller-Starck, G., M. Ziehe, and R. Schubert. 2005. Genetic diversity parameters associated with via-
bility selection, reproductive efciency, and growth in forest tree species. In: Scherer-Lorenzen,
M., Korner, C., Schulze, E.-D. (eds.), Forest Diversity and Function: Temperate and Boreal Systems.
Springer, Berlin, pp. 87–108.
Nabuurs, G.J. 1996. Quantication of herb layer dynamics under tree canopy. Forest Ecology and
Management 88 (1–2): 143–48.
Nagaike, T., T. Kamitani, and T. Nakashizuka. 1999. The effect of shelterwood logging on the diver-
sity of plant species in a beech (Fagus crenata) forest in Japan. Forest Ecology and Management 118
(1–3): 161–71.
Nakagawa, M., A. Kurahashi, M. Kaji, and T. Hogetsu. 2001. The effects of selection cutting on regen-
eration of Picea jezoensis and Abies sachalinensis in the sub-boreal forests of Hokkaido, northern
Japan. Forest Ecology and Management 146 (1–3): 15–23.
Nara, K. 2006. Ectomycorrhizal networks and seedling establishment during early primary succes-
sion. New Phytologist 169: 169–76.
Nathan, R. and H.C. Muller-Landau. 2000. Spatial patterns of seed dispersal, their determinants and
consequences for recruitment. Trends in Ecology and Evolution 15: 278–85.
Netherer, S. and A. Schopf. 2010. Potential effects of climate change on insect herbivores in European
forests—General aspects and the pine processionary moth as specic example. Forest Ecology
and Management 259 (4): 831–8.
Nicolini, E., D. Barthélémy and P. Heuret. 2000. Inuence de la densité du couvert forestier sur le
développement architectural de jeunes chênes sessiles, Quercus petraea (Matt.) Liebl. (Fagaceae),
en régénération forestière. Canadian Journal of Botany 78: 1–14.
Nopp-Mayr, U., I. Kempter, G. Muralt, and G. Gratzer. 2012. Seed survival on experimental dishes in
a central European old-growth mixed-species forest—effects of predator guilds, tree masting
and small mammal population dynamics. Oikos 121 (3): 337–46.
Nörr, R., M. Ganz, and A. Waechter. 2002. Wildlinge. Allgemeine Forstzeitschrift/Der Wald 5: 225–27.
Nyari, L. 2010. Genetic diverstiy, differentiation and spatial genetic structures in differently man-
aged adult European beech (Fagus sylvatica L.) stands and their regeneration. Forstarchiv 81:
156–64.
Nyland, R.N. 1996. Silviculture Concepts and Applications. McGraw-Hill, New York, NY.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
157Developing Restoration Strategies for Temperate Forests
Nyland, R.D. 2002. Silviculture: Concepts and Applications, 2nd ed. McGraw-Hill, New York.
O’Hanlon-Manners, D.L. and P.M. Kotanen. 2004. Logs as refuges from fungal pathogens for seeds
of Eastern hemlock (Tsuga canadensis). Ecology 85 (1): 284–89.
Oheimb, G.V., H.J. Ellenberg, J. Heuveldop, and W.-U. Kriebitzsch. 1999. Einuß der Nutzung unter-
schiedlicher Waldökosysteme auf die Artenvielfalt und -zusammensetzung der Gefäßpanzen
in der Baum-, Strauch- und Krautschicht unter besonderer Berücksichtigung von Aspekten des
Naturschutzes und des Verbißdruckes durch Wild. Mitteilungen der Bundesforschungsanstalt für
Forst- und Holzwirtschaft Hamburg 195: 279–450.
Økland, T., K. Rydgren, R.H. Økland, K.O. Storaunet, and J. Rolstad. 2003. Variation in environmen-
tal conditions, understorey species number, abundance and composition among natural and
managed Picea abies forest stands. Forest Ecology and Management 177 (1–3): 17–37.
Oliet, J. and D. Jacobs. 2012. Restoring forests: Advances in techniques and theory. New Forests 43
(5–6): 535–41.
Olson, B.E. and R.T. Wallander. 2002. Does ruminal retention time affect leafy spurge seed of varying
maturity? Journal Range Management 55: 65–69.
Olsthoorn, A.F., H.H. Bartelink, J.J. Gardiner, H. Pretzsch, H.J. Hekhuis, and A. Franc. 1999.
Management of mixed-species forest: Silviculture and economics. Wageningen, the Netherlands:
IBN Scientic Contributions 15.
Orlikowski, L.B. and G. Szkuta. 2004. First notice of Phytophthora ramorum on Calluna vulgaris, Photinia
fraseri and Pieris japonica in Polish container-grown ornamental nurseries. Phytopathologia
Polonica 33: 87–92.
Otto, J. 1996. Waldökologie, UTB, Stuttgart, 1994.
Ouden, J., P.A. Jansen, R. Smit, P.M. Forget, J.E. Lambert, R.E. Hulme, and S.B. Vander Wall, S.B., 2005.
Jays, mice and oaks: Predation and dispersal of Quercus robur and Q. petraea in North-western
Europe. In: Forget, P.M., Lambert, J., Vander Wall, S.B. (eds.), Seed Fate: Predation, Dispersal and
Seedling Establishment. CABI Publishing, Wallingford, pp. 223–40.
Övergaard, R., P. Gemmel, and M. Karlsson. 2007. Effects of weather conditions on mast year fre-
quency in beech (Fagus sylvatica) in Sweden. Forestry 80 (5): 555–65.
Owen, M.D.K. 1994. Impact of crop tolerance to specic herbicides on weed management systems:
Corn and soybeans. Proceeding of the North Central Weed Science Society. 49: 167–8.
Owens, J.N. 1995. Constraints to seed production: Temperate and tropical forest trees. Tree Physiology
15: 477–84.
Owens, J.N. and M.D. Blake. 1985. Forest tree seed production. A review of literature and recommen-
dations for future research. Environment Canada, Canadian Forest Service, Information Report
PI-X-53, 161 p.
Owens, J.N. and D.D. Fernando. 2007. Pollination and seed production in western white pine.
Canadian Journal of Forest Research 37 (2): 260–75.
Pabian, S.E., N.M. Ermer, W.M. Tzilkowski, and M.C. Bittingham. 2012. Effects of liming on forage
availability and nutrient content in a forest impacted by acid rain. PLoSONE 7 (6): e39755.
Pacala, S.W., C.D. Canham, J. Saponara, J.A. Silander, Jr., R.K. Kobe, and E. Ribbens. 1996. Forest
models dened by eld measurements: II. Estimation, error analysis and dynamics. Ecological
Monographs 66: 1–43.
Padilla, F.M. and F.I. Pugnaire. 2006. The role of nurse plants in the restoration of degraded environ-
ments. Frontiers in Ecology and Environment 4 (4): 196–202.
Pairon, M.C., M. Jonard, and A.L. Jacquemart. 2006. Modelling seed dispersal of black cherry, an
invasive forest tree: How microsatellites may help? Canadian Journal of Forest Research 36:
1385–94.
Pallardy, S.G. and J.L. Rhoads. 1993. Morphological adaptations to drought in seedlings of deciduous
angiosperms. Canadian Journal of Forest Research 23 (9): 1766–74.
Palmer, M.A. and S. Filoso. 2009. Restoration of ecosystems services for environmental markets.
Science 325 (5940): 575–76.
Panferov, O. and A. Sogachev. 2008. Inuence of gap size on wind damage variables in a forest.
Agricultural and Forest Meteorology 148 (11): 1869–81.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
158 Restoration of Boreal and Temperate Forests
Paquette, A., A. Bouchard, and A. Cogliastro. 2006. Survival and growth of under-planted trees:
Ameta-analysis across four biomes. Ecological Applications 16 (4): 1575–89.
Paquette, A. and C. Messier. 2011. The effect of biodiversity on tree productivity: From temperate to
boreal forests. Global Ecology and Biogeography 20 (1): 170–80.
Parker, W.C., D.C. Dey, S.G. Newmaster, K.A. Elliott, and E. Boysen. 2001. Managing succession in
conifer plantations: Converting young red pine (Pinus resinosa Ait.) plantations to native forest
types by thinning and underplanting. The Forestry Chronicle 77 (4): 721–34.
Paulsen, T. and G. Högstedt. 2002. Passage through bird guts increase germination and seedling
growth of Sorbus aucuparia. Functional Ecology 16: 608–12.
Penne, C., B. Ahrends, M. Deurer, and J. Böttcher. 2010. The impact of the canopy structure on the
spatial variability in forest oor carbon stocks. Geoderma 158 (3–4): 282–97.
Perala, D.A. and A.A. Alm. 1990. Regeneration silviculture of birch—A review. Forest Ecology and
Management 32:39–77.
Perea, R., A. San Miguel, and L. Gil. 2011. Leftovers in seed dispersal: Ecological implications of par-
tial seed consumption for oak regeneration. Journal of Ecology 99: 194–201.
Pérez-Ramos, I.M. and T. Marañón. 2008. Factors affecting post-dispersal seed predation in two coex-
isting oak species: Microhabitat, burial and exclusion of large herbivores. Forest Ecology and
Management 255 (8–9): 3506–14.
Peterken, G.F. and F.M.R. Huges. 1995. Restoration of oodplain forests in Britain. Forestry 68 (3):
187–202.
Peterson, C.J. and S.T. Pickett. 1995. Forest reorganization: A case study in an old-growth forest cata-
strophic blowdown. Ecology 76 (3): 763.
Petritan, A.M., B. von Lüpke, and I.C. Petritan. 2007. Effects of shade on growth and mortality of
maple (Acer pseudoplatanus), ash (Fraxinus excelsior) and beech (Fagus sylvatica) saplings. Forestry
80 (4): 397–412.
Piha, A., T. Kuuluvainen, H. Lindberg, and I. Vanha-Majamaa. 2013. Can scar-based re history
reconstructions be biased? An experimental study in boreal Scots pine. Canadian Journal of
Forest Research 43 (7): 669–75.
Ponder, F., Jr. 1997. Survival and growth of hardwood seedlings following preplanting-root treat-
ments and treeshelters. In: Pallardy, S.G., R.A. Cecich, H.G. Garrett, and P.S. Johnson (eds.),
Proceedings of the 11th Central Hardwood Forest Conference. General Technical Report. NC-188.
USDA Forest Service North Central Forest Experiment Station, St. Paul., pp. 332–40.
Ponge, J.-F., O. Zackrisson, N. Bernier, M.-C. Nilsson, and C. Gallet. 1998. The forest regeneration
puzzle. BioScience 48 (7): 523–30.
Pons, J. and J.G. Pausas. 2008. Modelling jay (Garrulus glandarius) abundance and distribution for
oak regeneration assessment in Mediterranean landscapes. Forest Ecology and Management 256:
578–84.
Poorbabaei, H. and A. Poor-Rostam. 2009. The effect of shelterwood silvicultural method on the
plant species diversity in a beech (Fagus orientalis Lipsky) forest in the north of Iran. Journal of
Forest Science 55 (8): 387–94.
Preuhsler, T., P. da Costa, and E. Maria. 1994. Growth of mixed-species regeneration below Pinus
shelter. Symposium of working groups of S4.01: Mensuration, Growth and Yield: MIXED
STANDS—Research Plots.Measurement and Results. In IUFRO 25–29 April, 207–17. Lousá/
Coimbra Portugal.
Priewasser, K., P. Brang, H. Bachofen, H. Bugmann, and T. Wohlgemuth. 2013. Impacts of salvage-
logging on the status of deadwood after windthrow in Swiss forests. European Journal of Forest
Research 132 (2): 231–40.
Putman, R.J. 1996. Ungulates in temperate forest ecosystems: Perspectives and recommendations for
future research. Forest Ecology and Management 88 (1–2): 205–14.
Pyšek, P. 1993. What do we know about Calamagrostis villosa?—A review of the species behaviour in
secondary habitats. Preslia 65: 1–20.
Pyšek, P., V. Jarošík, P.E. Hulme, J. Pergl, M. Hejda, U. Schaffner, and M. Vilà. 2012. A global
assessment of invasive plant impacts on resident species, communities and ecosystems: The
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
159Developing Restoration Strategies for Temperate Forests
interaction of impact measures, invading species’ traits and environment. Global Change Biology
18 (5): 1725–37.
Ran, F., C. Wu, G. Peng, H. Korpelainen, and C. Li. 2010. Physiological differences in Rhododendron
calophytum seedlings regenerated in mineral soil or on fallen dead wood of different decaying
stages. Plant Soil 337 (1–2): 205–15.
Rapp, J.M., E.J.B. McIntire, and E.E. Crone. 2013. Sex allocation, pollen limitation and masting in
whitebark pine. Journal of Ecology 101: 1345–52.
Raymond, P., S. Bédard, V. Roy, C. Larouche, and R. Tremblay. 2009. The irregular shelterwood sys-
tem: Review, classication, and potential application to forests affected by partial disturbances.
Journal of Forestry 107 (8): 405–13.
Reed, B.C., J.F. Brown, and D. Vanderzee. 1994. Measuring phenological variability from satellite
imagery, Journal of Vegetation Science 5 (5): 703–14.
Reich, P.B., D.S. Ellsworth and M.B. Walters. 1998. Leaf structure (specic leaf area) modulates pho-
tosynthesis–nitrogen relations: Evidence from within and across species and functional groups.
Functional Ecology 12: 948–58.
Reif, A. and M. Przybilla. 1995. On the regeneration of spruce (Picea abies) in the montane zone of the
Bavarian Forest National Park. Hoppea 56: 467–514.
Remmert, H. (ed.), 1991. The Mosaic-Cycle Concept of Ecosystems. Ecological Studies. Springer Berlin
Heidelberg, Berlin, Heidelberg.
Ren, H., H. Lu, J. Wang, N. Liu, and Q. Guo. 2012. Forest restoration in China: Advances, obstacles,
and perspectives. Tree and Forestry Science and Biotechnology 6 (1): 7–16.
Rey Benayas, J.M., A.C. Newton, A. Diaz, and J.M. Bullock. 2009. Enhancement of biodiversity and
ecosystem services by ecological restoration: A meta-analysis. Science 325 (5944): 1121–24.
Ribbens, E., J.A. Silander, and S.W. Pacala. 1994. Seedling recruitment in forests: Calibrating models
to predict patterns of tree seedling dispersion. Ecology 75: 1794–1806.
Richardson, D.M. 1998. Forestry trees as invasive aliens. Conservation Biology 12 (1): 18–26.
Ricklefs, R.E. 1977. Environmental heterogeneity and plant species diversity: A hypothesis. The
American Naturalist 111 (978): 376–81.
Ripple, W.J. and E.J. Larsen. 2001. The role of postre coarse woody debris in aspen regeneration.
Western Journal of Applied Forestry 16: 61–4.
Roberts, E.H. 1973. Predicting the storage life of seeds. Seed Science and Technology 1: 499–514.
Rodrigues, R.R., R.A. Lima, S. Gandol, and A.G. Nave. 2009. On the restoration of high diversity for-
ests: 30 years of experience in the Brazilian Atlantic Forest. Biological Conservation 142 (6): 1242–51.
Röhrig, E., N. Bartsch, A. Dengler, and B. von Lüpke. 2006. Waldbau auf ökologischer Grundlage: 91
Tabellen. 7., vollst. aktual. Au (Silviculture on an ecological foundation). UTB Forst- und
Agrarwissenschaften, Ökologie, Biologie 8310. Stuttgart: UTB.
Roovers, P., H. Gulinck, and M. Hermy. 2005. Experimental assessment of initial revegetation on
abandoned paths in temperate deciduous forest. Applied Vegetation Science 8 (2): 139–48.
Rosenvald, R. and A. Lõhmus. 2008. For what, when, and where is green-tree retention better than
clear-cutting? A review of the biodiversity aspects. Forest Ecology and Management 255 (1): 1–15.
Rosenvald, R., A. Lõhmus, A. Kiviste, R. Rosenvald, A. Lõhmus, and A. Kiviste. 2008. Preadaptation
and spatial effects on retention-tree survival in cut areas in Estonia. Canadian Journal of Forest
Research 38 (10): 2616–25.
Ross, S.D. 1989. Temperature inuences on reproductive development in conifers. In: MacIver, D.C.,
R.B. Street, and A.N. Auclair (eds.), Forest Renewal and Forest Production: Forest Climate, ‘86 Symp.
Can. Gov. Printing Cent., Ottawa, Ont., pp. 40–43.
Ross, S.D. and R.P. Pharis. 1985. Promotion of owering in tree crops: Different mechanisms and
techniques, with special reference to conifers. In: Cannell M.G.R., and J.E. Jackson (eds.),
Attributes of Trees as Crop Plants. Inst. Terrestrial Ecology, Monks Wood Exp. Stn., Abbots Ripton,
Huntingdon, UK, pp. 383–97.
Rother, D.C., Jordanob, P., Rodriguesc, R.R., and M.A. Pizod. 2013. Demographic bottlenecks in
tropical plant regeneration: A comparative analysis of causal inuences. Perspectives in Plant
Ecology, Evolution and Systematics 15: 86–96.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
160 Restoration of Boreal and Temperate Forests
Rowell, A. and P.F. Moore. 2000. Global Review of Forest Fires. Gland: IUCN The World Conservation
Union; Forests for Life Programme Unit WWF International.
Royo, A.A. and W.P. Carson. 2006. On the formation of dense understory layers in forests worldwide:
Consequences and implications for forest dynamics, biodiversity, and succession. Canadian
Journal of Forest Research 36 (6): 1345–62.
Royo, A.A. and T.E. Ristau. 2012. Stochastic and deterministic processes regulate spatio-temporal
variation in seed bank diversity. Journal of Vegetation Science 24: 724–34.
Rüdinger, M.C.D., J. Glaeser, I. Hebel, and A. Dounavi 2008. Genetic structures of common ash
(Fraxinus excelsior) populations in Germany at sites differing in water regimes. Canadian Journal
of Forest Research 38: 1199–1210.
Rumble, M.A., T. Pella, J.C. Sharps, A.V. Carter, and J.B. Parrish. 1996. Effects of logging slash on
aspen regeneration in grazed clearcuts. Prairie Naturalist 28: 199–210.
Runkle, J.R. 1982. Patterns of disturbance in some old-growth mesic forests of eastern North America.
Ecology 63 (5): 1533.
Runkle, J.R. 1985. Disturbance regimes in temperate forests. In: Pickett, S.T.A. and P.S. White (eds.),
The Ecology of Natural Disturbance and Patch Dynamics. Academic Press, New York, pp. 17–33.
Runkle, J.R. 1989. Synchrony of regeneration, gaps, and latitudinal differences in tree species diver-
sity. Ecology 70: 546–7.
Ruscoe, W.A., J.S. Elkinton, D. Choquenot, and R.B. Allen. 2005. Predation of beech seed by mice:
Effects of numerical and functional responses. Journal of Animal Ecology 74: 1005–19.
Rust, S. and P.S. Savill 2000. The root system of Fraxinus excelsior and Fagus sylvatica and their com-
petitive relationships. Forestry. 73: 499–508.
Ryan, K.C. 2002. Dynamic interactions between forest structure and re behavior in boreal ecosys-
tems. Silva Fennica 36 (1): 13–39.
Sagheb-Talebi, K. and J.P. Schütz. 2002. The structure of natural oriental beech (Fagus orientalis) for-
ests in the Caspian region of Iran and potential for the application of the group selection sys-
tem. Forestry 75 (4): 465–72.
Sagnard, F., C. Pichot, G.G. Vendramin, and B. Fady. 2011. Effects of seed dispersal, adult tree and
seedling density on the spatial genetic structure of regeneration at ne temporal and spatial
scales. Tree Genetics and Genomes 7, 37–48.
Sanchez, E., R. Gallery, and J.W. Dalling. 2009. Importance of nurse logs as a substrate for the regen-
eration of pioneer tree species on Barro Colorado Island, Panama. Journal of Tropical Ecology
25(04): 429.
Santiago, L.S. 2000. Use of coarse woody debris by the plant community of a Hawaiian montane
cloud forest. Biotropica 32 (4a): 633–41.
Schirmer, W., T. Diehl and C. Ammer. 1999. Zur entwicklung junger eichen unter kiefernschirm.
Forstarchiv 70: 57–65.
Schliemann, S.A. and J.G. Bockheim. 2011. Methods for studying treefall gaps: A review. Forest
Ecology and Management 261 (7): 1143–51.
Schmidt, W., 2006. Temporal variation in beech masting (Fagus sylvatica L.) in a limestone beech forest
(1981–2004). Allgemeine Forst- und Jagdzeitung 177: 9–19.
Schmiedel, D., F. Huth, and S. Wagner. 2013. Using data from seed dispersal modelling to manage
invasive tree species: The example of Fraxinus pennsylvanica in Europe. Environment Management
52 (4): 851–60.
Schröder, T., R. Kehr, R., Z. Prochazkova, and J.R. Sutherland. 2004. Practical methods for estimat-
ing the infection rate of Quercus robur acorn seedlots by Ciboria batschiana. Forest Pathology 34:
187–96.
Schupp, E.W. 1995. Seed-seedling conicts, habitat choice, and patterns of plant recruitment. American
Journal of Botany 82 (3): 399.
Schupp, E.W., P. Jordano, and J.M. Gómez. 2010. Seed dispersal effectiveness revisited: A conceptual
review. New Phytologist 188: 333–53.
Schurr, F.M., O. Steinitz, and R. Nathan. 2008. Plant fecundity and seed dispersal in spatially het-
erogeneous environments: Models, mechanisms and estimation. Journal of Ecology 96: 628–41.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
161Developing Restoration Strategies for Temperate Forests
Schütz, J.-P. 1999. Praktische bedeutung der überführung für die umsetzung der plenteridee. Forst
und Holz 54 (104–8).
Schütz, J.-P. 2002. Silvicultural tools to develop irregular and diverse forest structures. Forestry 75 (4):
329–37.
Seidl, R., M.J. Schelhaas, M. Lindner, and M.J. Lexer. 2009. Modelling bark beetle disturbances in a
large scale forest scenario model to assess climate change impacts and evaluate adaptive man-
agement strategies. Regional Environmental Change 9: 101–19.
Sheffer, E., C.D. Canham, J. Kigel, and A. Perevolotsky. 2013. Landscape-scale density-dependent
recruitment of oaks in planted forests. More is not always better. Ecology 94: 1718–28.
Sheil, D. 2001. Long-term observations of rain forest succession, tree diversity and responses to dis-
turbance. Plant Ecology 155 (2): 183–99.
Shibata, M. and T. Nakashizuka. 1995. Seed and seedling demography of four co-occurring Carpinus
species in a temperate deciduous forest. Ecology 76: 1099–108.
Siddique, I., V.L. Engel, J.A. Parrotta, D. Lamb, G.B. Nardoto, J.P.H.B. Ometto, L.A. Martinelli, and
S. Schmidt. 2008. Dominance of legume trees alters nutrient relations in mixed species forest
restoration plantings within seven years. Biogeochemistry 88 (1): 89–101.
Siles, G., P.J. Rey, and J.M. Alcántara. 2010. Post-re restoration of Mediterranean forests: Testing
assembly rules mediated by facilitation. Basic Applied Ecology 11 (5): 422–31.
Silvertown, J. 2004. Plant coexistence and the niche. Trends in Ecology and Evolution (Amst.) 19 (11):
605–11.
Sipe, T.W. and F.A. Bazzaz. 1994. Gap partitioning among maples (Acer) in Central New England:
Shoot architecture and photosynthesis. Ecology 75 (8): 2318.
Sipe, T.W. and F.A. Bazzaz. 1995. Gap partitioning among maples (Acer) in Central New England:
Survival and growth. Ecology 76: 1587–1602.
Smit, C., D.P. Kuijper, D. Prentice, M.J. Wassen, and J.P. Cromsigt. 2012. Coarse woody debris facili-
tates oak recruitment in Białowieża Primeval Forest, Poland. Forest Ecology and Management 284:
133–41.
Smit, C., M. Gusberti, and H. Müller-Schärer. 2006. Safe for saplings; safe for seeds? Forest Ecology and
Management 237 (1–3): 471–77.
Smith, K.T., W.C. Shortle, J. Jellison, J. Connolly, J., and J. Schilling. 2007. Concentrations of Ca and
Mg in early stages of sapwood decay in red spruce, eastern hemlock, red maple, and paper
birch. Canadian Journal of Forest Research 37: 957–65.
Sollins, P., S.P. Cline, T. Verhoeven, D. Sachs, and G. Spycher. 1987. Patterns of log decay in old-
growth Douglas-r forests. Canadian Journal of Forest Research 17 (12): 1585–95.
Sonohat, G., H. Sinoquet, V. Kulandaivelu, D. Combes, and F. Lescourret. 2006. Three-dimensional
reconstruction of partially 3D-digitized peach tree canopies. Tree Physiology 26(3): 337–51.
Soons, M.B. 2006. Wind dispersal in freshwater wetlands: Knowledge for conservation and restora-
tion. Applied Vegetation Science 9: 2721–278.
Sork, V.L., J. Bramble, and O. Sexton. 1993. Ecology of mast-fruiting in three species of North
American deciduous oaks. Ecology 74: 528–41.
Stimm, B. and K. Böswald. 1994. Die häher im visier. Zur Ökologie und waldbaulichen Bedeutung
der Samenausbreitung durch Vögel (The jay in focus: Ecology and silvicultural relevance of
seed dispersal by birds). Forstwissenschaftliches Centralblatt 113: 204–23.
Stimm, B. and T. Knoke. 2004. Hähersaaten: ein Literaturüberblick zu waldbaulichen und ökono-
mischen Aspekten (Sowing by jays: A literature review to silviculture and forest economy).
Forst Holz 59: 531–4.
St. John, T. 1997. Arbuscular mycorrhizal inoculation in nursery practice. In: Landis, T.D., South, D.B.
(technical coordinators.), National Proceedings, Forest and Conservation Nursery Associations. US
Department of Agriculture, Forest Service, Portland (OR), Pacic Northwest Research Station
General Technical Report PNW-GTR-389. pp. 152–58.
Stöckli, B. 1995. Decaying wood for natural regeneration in montane forests. Forest and Timber 16: 8–15.
Stoehr, M.U. and Y.A. El-Kassaby. 2011. Challenges facing the forest industry in relation to seed dor-
mancy and seed quality. Methods in Molecular Biology 773: 3–15.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
162 Restoration of Boreal and Temperate Forests
Stokland, J.N., J. Siitonen, and B.G. Jonsson. 2012. Biodiversity in Dead Wood. Ecology, biodiversity,
and conservation. Cambridge University Press, New York.
Stoyan, D. and S. Wagner. 2001. Estimating the fruit dispersion of anemochorous forest trees.
Ecological Modeling 145: 35–47.
Streiff, R., T. Labbe, R. Bacilieri, H. Steinkellner, J. Glössl, and A. Kremer. 1998. Within population
genetic structure in Quercus robur L. and Quercus petraea (Matt.) Liebl. assessed with isozymes
and microsatellites. Molecular Ecology 7: 317–28.
Suchant, R., R. Baritz, and F. Armbruster. 2000. Werden Wildlinge weniger verbissen? Allgemeine
Forst- u.Jagd-Zeitung 5: 251–54.
Svoboda, M., S. Fraver, P. Janda, R. Bače, and J. Zenáhlíková. 2010. Natural development and regen-
eration of a Central European montane spruce forest. Forest Ecology and Management 260 (5):
707–14.
Sydes, C. and J.P. Grime. 1981. Effects of tree leaf litter on herbaceous vegetation in deciduous wood-
land: I. Field investigations. Journal of Ecology 69 (1): 237–48.
Szewczyk, J. and J. Szwagrzyk. 1996. Tree regeneration on rotten wood and on soil in old-growth
stand. Vegetatio 122 (1): 37–46.
Tabaku, V. and P. Meyer. 1999. Lückenmuster albanischer und mitteleuropäischer Buchenwälder
unterschiedlicher Nutzungsintensität. Forstarchiv 70: 87–97.
Tappeiner, J.C. and R.G. Wagner. 1987. Principles of silvicultural prescriptions for vegetation manage-
ment. In: J.D. Walstad and P.J. Kuch (eds.), Forest Vegetation Management for Conifer Production.
John Wiley, New York, N.Y. pp. 399–429.
Tasker, E.M. and R.A. Bradstock. 2006. Inuence of cattle grazing practices on forest understorey
structure in north-eastern New South Wales. Austral Ecology 31 (4): 490–502.
Temperli, C.W. 2012. Climate change, large-scale disturbances and adaptive forest management.
Diss. No. 20899, ETH Zürich.
Thomas, S.C. and J. MacLellan. 2004. Boreal and temperate forests. In: Owens J.N., and H.G. Lund
(eds.), Forests and Forest Plants. Encyclopedia of Life Support Systems (EOLSS); UNESCO, Eolss
Publishers, Oxford, UK, pp. 152–75.
Thomasius, H. and P.A. Schmidt. 2004. Forest, forest management and environment. In: BuchwaldK.,
and W. Engelhardt (eds.), Environmental Protection—Basics and Practice. Economica 10, Bonn, 435p.
Thomsen, K.A., E.D. Kjær. 2002. Variation between single tree progenies of Fagus sylvatica in seed
traits, and its implications for effective population numbers. Silvae Genetica 51: 183–90.
Tilmann, D. 1982. Resource competition and community structure. Princeton Monographs in
Population Biology 17. Princeton University Press, Princeton, NJ.
Trabucchi, M., C. Puente, F.A. Comin, G. Olague, and S.V. Smith. 2012. Mapping erosion risk at
the basin scale in a Mediterranean environment with opencast coal mines to target restoration
actions. Regional Environmental Change 12 (4): 675–87.
Trotsiuk, V., M.L. Hobi, and B. Commarmot. 2012. Age structure and disturbance dynamics of the
relic virgin beech forest Uholka (Ukrainian Carpathians). Forest Ecology and Management 265:
181–90.
Ulanova, N.G. 2000. The effects of windthrow on forests at different spatial scales: A review. Forest
Ecology and Management 135 (1–3): 155–67.
Urbanska, K.M., N.R. Webb, and P.J. Edwards, (eds.) 1997. Restoration Ecology and Sustainable
Development. Cambridge University Press, Cambridge, UK.
van Couwenberghe, R., 2011. Effets des facteurs environnementaux sur la distribution et l’abondance
des espèces végétales forestières aux échelles locales et régionales. Ecosystems. AgroParisTech,
French. Available at: https://pastel.archives-ouvertes.fr/pastel-00604628].
van Couwenberghe, R., C. Collet, E. Lacombe, J.-C. Pierrat, and J.-C. Gégout. 2010. Gap partitioning
among temperate tree species across a regional soil gradient in windstorm-disturbed forests.
Forest Ecology and Management 260 (1): 146–54.
Vandekerkhove, K., L. de Keersmaeker, N. Menke, P. Meyer, and P. Verschelde. 2009. When nature
takes over from man: Dead wood accumulation in previously managed oak and beech wood-
lands in North-western and Central Europe. Forest Ecology and Management 258 (4): 425–35.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
163Developing Restoration Strategies for Temperate Forests
Vandenberghe, C., F. Freléchoux, F. Gadallah, and A. Buttler. 2006. Competitive effects of herbaceous
vegetation on tree seedling emergence, growth and survival: Does gap size matter? Journal of
Vegetation Science 17 (4): 481–88.
Van Der Meer, P.J., P. Dignan, and A.G. Saveneh. 1999. Effect of gap size on seedling establishment,
growth and survival at three years in mountain ash (Eucalyptus regnans F. Muell.) forest in
Victoria, Australia. Forest Ecology and Management 117 (1–3): 33–42.
Vanha-Majamaa, I. and E.-S. Tuittila. 1996. Seedling establishment after prescribed burning of a clear-
cut and a partially cut mesic boreal forest in southern Finland. Silva Fennica 31 (1): 31–45.
Vanha-Majamaa, I., S. Lilja, R. Ryömä, J.S. Kotiaho, S. Laaka-Lindberg, H. Lindberg, P. Puttonen,
P. Tamminen, T. Toivanen, and T. Kuuluvainen. 2007. Rehabilitating boreal forest structure
andspecies composition in Finland through logging, dead wood creation and re: The EVO
experiment. Forest Ecology and Management 250 (1–2): 77–88.
van Hees, A.F. 1997. Growth and morphology of pedunculate oak (Quercus robur L.) and beech (Fagus
sylvatica L.) seedlings in relation to shading and drought. Annales of Forest Science 54 (1): 9–18.
van Oijen, D., M. Feijen, P. Hommel, J. Ouden, and R. Waal. 2005. Effects of tree species composition
on within-forest distribution of understorey species. Applied Vegetation Science 8 (2): 155–66.
Vanselow, K. 1949. Theorie und Praxis der natürlichen Verjüngung im Wirtschaftswald (Theory and
Practice of Natural Regeneration in Managed Forests). 2nd ed., Neumann Verlag, Radebeul,
Berlin.
Verheyen, K., G.R. Guntenspergen, B. Biesbrouck, and M. Hermy. 2003. An integrated analysis of the
effects of past land use on forest herb colonization at the landscape scale. Journal of Ecology 91
(5): 731–42.
von Lüpke, B. 1987. Einüsse von altholzüberschirmung und bodenvegetation auf das wachstum
junger buchen und traubeneichen (Effect of canopy structure and ground vegetation on growth
of young beeches and oaks). Forstarchiv 58: 18–24.
von Lüpke, B. and K. Hauskeller-Bullerjahn. 2004. Beitrag zur modellierung der jungwuchsentwick-
lung am beispiel von traubeneichen-buchen-mischverjüngung. Allgemeine Forst- u.Jagd-Zeitung
175: 61–69.
Wada, N. and E. Ribbens. 1997. Japanese maple (Acer palmatum var. Matsumurae, Aceraceae)
recruitment patterns: Seeds, seedlings, and saplings in relation to conspecic adult neighbors.
American Journal of Botany 84: 1294–300.
Wagner, S. 1999. Ökologische Untersuchungen zur Initialphase der Naturverjüngung in Eschen-
Buchen-Mischbeständen. Schriftenreihe der Forstlichen Fakultät der Uni Göttingen und der
Niedersächsischen Forstlichen Versuchsanstalt Göttingen, Sauerländer’s Verlag.
Wagner, S., C. Collet, P. Madsen, T. Nakashizuka, R.D. Nyland, and K. Sagheb-Talebi. 2010. Beech
regeneration research: From ecological to silvicultural aspects. Forest Ecology and Management
259: 2172–82.
Wagner, S., H. Fischer, and F. Huth. 2011. Canopy effects on vegetation caused by harvesting and
regeneration treatments. European Journal of Forest Research 130 (1): 17–40.
Walker, L.R., J. Walker, and R.J. Hobbs. 2007. Linking Restoration and Ecological succession. Springer
series on environmental management. New York, NY: Springer.
Walters, M.B. and P.B. Reich. 1997. Growth of Acer saccharum seedlings in deeply shaded understo-
ries of northern Wisconsin: Effects of nitrogen and water availability. Canadian Journal of Forest
Research 27: 237–47.
Walters, M.B. and P.B. Reich. 2000. Seed size, nitrogen supply, and growth rate affect tree seedling
survival in deep shade. Ecology 81: 1887–901.
Wang, C.W. and T.B. Smith. 2002. Closing the seed dispersal loop. Trends in Ecology and Evolution 17:
379–85.
Watt, A.S. 1923. On the ecology of British beechwoods with special reference to their regeneration.
Journal of Ecology 11: 1–48.
Watt, A.S. 1925. On the Ecology of British Beechwoods with Special Reference to Their Regeneration:
Part II, Sections II and III The development and structure of beech communities on the Sussex
Downs (continued). Journal of Ecology 13: 27–73.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016
164 Restoration of Boreal and Temperate Forests
Watt, A.S. 1947. Pattern and process in the plant community. Journal of Ecology 35: 1–22.
Weiland, J.E., B.R. Beck, and A. Davis. 2013. Pathogenicity and virulence of Pythium species obtained
from forest nursery soils on Douglas-r seedlings. Plant Disease 2013. 97: 744–8.
Wenny, D.G. 2000. Seed dispersal, seed predation, and seedling recruitment of a Neotropical mon-
tane tree. Ecological Monographs 70: 331–51.
Wiedemann, E. 1927. Über den künstlichen gruppenweisen Voranbau von Tanne und Buche.
Allgemeine Forst- u.Jagd-Zeitung 103: 433–52.
Willoughby, I. and R.L. Jinks. 2009. The effect of duration of vegetation management on broadleaved
woodland creation by direct seeding. Forestry 82 (3): 343–59.
Willson, M.F. 1993. Dispersal mode, seed shadows, and colonization patterns. Vegetatio 107/108:
261–80.
Wojczulanis, B. 2002. Forest Ecosystems of the Karkonosze National Park. Agencja Fotograczno-
Wydawnicza, Mazury.
Wolf, H. 2003. EUFORGEN. Technical guidelines for genetic conservation and use for Silver r (Abies
alba). International plant Genetic resources institute, Rome, Italy. Available at: http://www.
euforgen.org/publications/publication/silver-r-emabies-albaem/.
Yamamoto, S.-I. 1992. The gap theory in forest dynamics. The Botanical Magazine, Tokyo 105: 375–83.
Yamamoto, S.-I. 1995. Gap characteristics and gap regeneration in subalpine old-growth coniferous
forests, central Japan. Ecological Research 10: 31–39.
Zeibig, A., J. Diaci, and S. Wagner. 2005. Gap disturbance patterns of a Fagus sylvatica virgin for-
est remnant in the mountain vegetation belt of Slovenia. Forest Snow and Landscape Research
79:69–80.
Zerbe, S. 1998. Potential natural vegetation: Validity and applicability in landscape planning and
nature conservation. Applied Vegetation Science 1: 165–72.
Zerbe, S. 2002. Restoration of natural broad-leaved woodland in Central Europe on sites with conif-
erous forest plantations. Forest Ecology and Management 167 (1–3): 27–42.
Zerbe, S. and A. Brande. 2003. Woodland degradation and regeneration in Central Europe during the
last 1,000 years—A case study in NE Germany. Phytocoenologia 33 (4): 683–700.
Zerbe, S. and D. Kreyer. 2007. Inuence of different forest conversion strategies on ground vegetation
and tree regeneration in pine (Pinus sylvestris L.) stands: A case study in NE Germany. European
Journal of Forest Research 126 (2): 291–301.
Zerbe, S. and G. Wiegleb (eds.), 2009. Renaturierung von Ökosystemen in Mitteleuropa. Spektrum
Akademischer Verlag, Heidelberg.
Zielonka, T. 2006. When does dead wood turn into a substrate for spruce replacement? Journal of
Vegetation Science 17(6): 739–46.
Zielonka, T. and M. Niklasson. 2001. Dynamics of dead wood and regeneration pattern in natural
spruce forest in the Tatra Mountains, Poland. Ecological Bulletin 49: 159–63.
Zielonka, T. and G. Piątek. 2004. The herb and dwarf shrubs colonization of decaying logs in subal-
pine forest in the Polish Tatra Mountains. Plant Ecology 172 (1): 63–72.
Zimmerman, J.K., W.M. Pulliam, D.J. Lodge, V. Quiñones-Orla, N. Fetcher, S. Guzmán-Grajales, J.A.
Parrotta etal. 1995. Nitrogen immobilization by decomposing woody debris and the recovery
of tropical wet forest from hurricane damage. Oikos 72 (3): 314.
Zywiec, M. and T. Zielonka. 2013. Does a heavy fruit crop reduce the tree ring increment? Results
from a 12-year study in a subalpine zone. Trees 27: 1365–73.
Downloaded by [Ulrike Hagemann] at 00:24 04 April 2016