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Simulated long-term effects of varying tree retention on wood production, dead wood and carbon stock changes

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Abstract

Boreal forests are an important source of timber and pulp wood, but provide also other products and services. Utilizing a simulation program and field data from a tree retention experiment in a Scots pine forest in central Sweden, we simulated the consequences during the following 100 years of various levels of retention on production of merchantable wood, dead wood input (as a proxy for biodiversity), and carbon stock changes. At the stand level, wood production decreased with increased retention levels, while dead wood input and carbon stock increased. We also compared 12 scenarios representing a land sharing/land sparing gradient. In each scenario, a constant volume of wood was harvested with a specific level of retention in a 100-ha landscape. The area not needed to reach the defined volume was set-aside during a 100-year rotation period, leading to decreasing area of set-asides with increasing level of retention across the 12 scenarios. Dead wood input was positively affected by the level of tree retention whereas the average carbon stock decreased slightly with increasing level of tree retention. The scenarios will probably vary in how they favor species preferring different substrates. Therefore, we conclude that a larger variation of landscape-level conservation strategies, also including active creation of dead wood, may be an attractive complement to the existing management.

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... The value of deadwood has been increasingly recognized, and currently the aim to increase deadwood quantity is imbedded in forest policies in many regions (Jonsson et al., 2016;European Commission, 2022). The permanent retention of trees will inevitably increase the availability of deadwood in managed forests (Roberge et al., 2015;Santaniello et al., 2017). However, the long-term dynamics of deadwood originating from retention trees, and the level of retention required to maintain sufficient quantity and variation of deadwood for the conservation of saproxylic diversity, are poorly known. ...
... the unburned stands, the immediate post-treatment deadwood pulse was weaker, but continuous formation of deadwood remains possible, although at a slow pace due to the low mortality rate of surviving trees. Retention level had a significant effect on deadwood profiles, since a higher retention level provides a larger pool of retention trees that will die and form deadwood Santaniello et al., 2017). However, the amount of formed deadwood was not directly proportionate to retained volume since retention level influenced the mortality rate of retained trees (see also Xing et al., 2018). ...
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Deadwood is essential for species diversity in forests. Forest management has led to the shortage of deadwood in managed forests and, consequently, to the decline of biodiversity. Prescribed burning and tree retention during harvests may promote deadwood formation, but the long-term effectiveness of these methods is not known. We examined patterns of tree mortality and deadwood dynamics following tree retention and prescribed burning in Finnish boreal forests in a large-scale replicated field experiment with two factors: retention level (10 or 50 m3/ha) and burning (burned or unburned). We monitored 2744 trees individually for 20 years. Deadwood input was initially high after the treatments, since nearly all retention trees on the burned sites and about one third of the trees on the unburned sites died within four years. For the rest of the monitoring period, deadwood input was much lower since the mortality rate of retention trees decreased to a level similar to the background mortality rate. After 20 years from the treatments, deadwood volume varied from about 40 m3/ha on the burned sites with 50 m3/ha retention to about 5 m3/ha on the unburned sites with 10 m3/ha retention. Prescribed burning altered deadwood composition e.g. via the complete mortality of fire-susceptible tree species. Still, deadwood diversity was mainly affected by retention level. Lastly, prescribed burning generated high numbers of snags, which fell rather quickly, with an estimated maximal longevity of 49 years. We conclude that the combination of a high retention level and prescribed burning produces high volumes of diverse deadwood, and thereby has the potential to support the conservation of deadwood-associated biodiversity in managed forests. However, the stand-scale continuity of deadwood throughout the forestry rotation period is still uncertain. The application of management methods should be adjusted at the landscape level to ensure the continuity of deadwood habitats.
... However, the latter conclusion is somewhat compromised by the fact that most of the studies allow for reduced harvest volume as a result of extended rotation length. The only exception we found was [18], in which the authors simulated the effects of different levels of tree retention on forest carbon stocks, while requiring that wood production remained the same in all scenarios. When harvest volumes are permitted to decrease with extended rotation length, the results depend on other assumptions, primarily on the size of substitution benefits from using wood in place of non-woody materials. ...
... As previously discussed, most studies allow harvest volume to vary while studying the effects of extending rotation length, with the notable exception of [18], whose authors stated, "we are not aware of any study that keeps the wood production constant, as we did in this study" (p. 43). ...
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We presented a case study and associated method for stand scale assessment of the duration of the climate change mitigation benefit provided by increasing forest harvest age (i.e., the age a stand is harvested). We used stand yield curves and newly developed equations to estimate carbon stocks in various boreal forest ecosystem pools in Ontario, Canada. The proposed method was applied to forest identified as available for harvesting in management plans for three forest management units with a combined area of more than 1900 km2. Our analysis indicated that a 10-year increase in harvest age did not provide a mitigation benefit (reduced carbon stock) in about half the available harvest area (45.5%, 61.9%, and 62.1% of the total available harvest area in the management units). Increasing the harvest age by 10 years resulted in a mitigation benefit lasting longer than 25 years for 15.1%, 16.0%, and 13.0% of the total available harvest area in the management units. The results suggest that increasing harvest age may have limited mitigation potential in Ontario’s managed boreal forests in the short-term but can reduce overall carbon stocks in the longer term.
... However, the latter conclusion is somewhat compromised by the fact that most of the studies allow for reduced harvest volume as a result of extended rotation length. The only exception we found was [18], in which the authors simulated the effects of different levels of tree retention on forest carbon stocks, while requiring that wood production remained the same in all scenarios. When harvest volumes are permitted to decrease with extended rotation length, the results depend on other assumptions, primarily on the size of substitution benefits from using wood in place of non-woody materials. ...
... As previously discussed, most studies allow harvest volume to vary while studying the effects of extending rotation length, with the notable exception of [18], whose authors stated, "we are not aware of any study that keeps the wood production constant, as we did in this study" (p. 43). ...
Article
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We presented a case study and associated method for stand scale assessment of the duration of the climate change mitigation benefit provided by increasing forest harvest age (i.e., the age a stand is harvested). We used stand yield curves and newly developed equations to estimate carbon stocks in various boreal forest ecosystem pools in Ontario, Canada. The proposed method was applied to forest identified as available for harvesting in management plans for three forest management units with a combined area of more than 1900 km2. Our analysis indicated that a 10-year increase in harvest age did not provide a mitigation benefit (reduced carbon stock) in about half the available harvest area (45.5%, 61.9%, and 62.1% of the total available harvest area in the management units). Increasing the harvest age by 10 years resulted in a mitigation benefit lasting longer than 25 years for 15.1%, 16.0%, and 13.0% of the total available harvest area in the management units. The results suggest that increasing harvest age may have limited mitigation potential in Ontario’s managed boreal forests in the short-term but can reduce overall carbon stocks in the longer term.
... Stands also differed in the site productivity. There were six sites with lower site index (TM3, ETO3, TM10, ETV10, ETV30, and EFF50) and six with high site index (Santaniello et al., 2017). See Table 1 for specific characteristics of the stands. ...
... The H100 (dominant height at 100 years of age) site index for each stand was estimated using standard methods based on site characteristics (altitude, latitude, field and bottom layer vegetation, water availability, and soil texture). Further details are available in (Santaniello et al., 2017). ...
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The excessive simplification of forest structure associated with clear-cutting can carry risks for biodiversity. Tree retention is an alternative practice that maintains greater structural diversity, but its effects on climate change impacts relative to conventional harvesting are largely unexplored. By integrating field measurements from 12 forest stands with modelling approaches, we investigated the post-harvest effects on radiative forcing of tree retention in a Swedish boreal pine forest. In the near-term, impacts from carbon fluxes and surface albedo were of the same order of magnitude but with opposite sign (warming for carbon and cooling for albedo), with a net warming effect. In the long-term, the net effect turns to cooling, as the forest becomes a strong carbon sink. Retention had a significant effect on climate in the near-term, where differences between the various retention levels are more evident. At increasing tree retention, warming impacts from carbon fluxes tend to decrease, but cooling contributions from surface albedo are less pronounced. Balancing these effects, we find a net climate warming that increases with tree retention.
... Ka lageraiel elurikkuse kaitseks säilitatavatel säilikpuudel on vähemalt lühiajaliselt positiivne mõju kliimamuutuste leevendamisele. Säilikpuudes salvestunud süsinik jääb raiejärgselt metsa alles (Santaniello et al., 2017), säilikpuude kasv (ja süsiniku sidumine) suu reneb kohe pärast raiet (Thorpe et al., 2007) erinevalt metsa uuenduse puudest, millel arvestatava puidumahu kasvu saavutamine võtab aastaid aega. Säilikpuud mõjutavad ka raiejärgseid muutusi metsamullas. ...
... viii) Puiduvajaduste katmiseks ja majandusliku tulu säilitamiseks võib metsad jagada erineva intensiivsusega majandatavateks puistuteks (nt Noormets & Nouvellon, 2015;Carpentier et al., 2017;Santaniello et al., 2017). Näiteks Eesti tingimustes võiks majandada intensiivselt põllumaadele rajatud esimese põlvkonna metsi, mille elustikuväärtus on väike, ning väheintensiivselt suure elustikuväärtusega metsi. ...
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The results of scientific studies dealing with the influence of forest management on carbon dynamics are often controversial. Substituting fossil fuels with wood is not always a climate-friendly solution, and besides, it has often a negative impact on biodiversity. The current paper reviews the literature about the influence of different forest management and timber use options on climate change and brings out the accompanying consequences on biodiversity in temperate and boreal climate zones. The forest’s ability to sequestrate and store carbon can be enlarged by appropriate forest management planning and practices. Generally, for mitigation of climate change, the moderate (not intensive) forest management is most favourable, but intensification of management enhances global warming, since forest carbon storage in tree biomass and soil decreases. The mitigation of climate change is just one of the many roles of forest, and climate policy actions cannot come at the expense of species diversity. The complex studies dealing with several forest goals conclude that high carbon store and biodiversity protection do not contradict each other, but the achievement of maximum economic profit at the same time is not possible. The mitigation of climate change and wildlife protection is most effective when it is first of all the forests with a high biodiversity that are managed less intensively. Concerning climate change, the most negative forest biomass use is wood combustion. It is reasonable to burn only such biomass (cut and industrial residues) which cannot be used for producing goods holding carbon for a long time.
... Retention forestry, which creates these characteristics, suggests that forest stands are only partially cut, leaving single trees or groups of trees that age and die on site. Thus, the retention increases the forest dead wood C pool, but decreases the production of merchantable timber (Nunery and Keeton, 2010;Roberge et al., 2015;Santaniello et al., 2017). On the other hand, retention trees have positive impact on diversity of mycorrhiza, which determine the capacity of seedlings to take up water and nutrients (Korkama et al., 2006;Sterkenburg et al., 2019). ...
Article
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The global forest carbon (C) stock is estimated at 662 Gt of which 45% is in soil organic matter. Thus, comprehensive understanding of the effects of forest management practices on forest soil C stock and greenhouse gas (GHG) fluxes is needed for the development of effective forest-based climate change mitigation strategies. To improve this understanding, we synthesized peer-reviewed literature on forest management practices that can mitigate climate change by increasing soil C stocks and reducing GHG emissions. We further identified soil processes that affect soil GHG balance and discussed how models represent forest management effects on soil in GHG inventories and scenario analyses to address forest climate change mitigation potential. Forest management effects depend strongly on the specific practice and land type. Intensive timber harvesting with removal of harvest residues/stumps results in a reduction in soil C stock, while high stocking density and enhanced productivity by fertilization or dominance of coniferous species increase soil C stock. Nitrogen fertilization increases the soil C stock and N2O emissions while decreasing the CH4 sink. Peatland hydrology management is a major driver of the GHG emissions of the peatland forests, with lower water level corresponding to higher CO2 emissions. Furthermore, the global warming potential of all GHG emissions (CO2, CH4 and N2O) together can be ten-fold higher after clear-cutting than in peatlands with standing trees. The climate change mitigation potential of forest soils, as estimated by modelling approaches, accounts for stand biomass driven effects and climate factors that affect the decomposition rate. A future challenge is to account for the effects of soil preparation and other management that affects soil processes by changing soil temperature, soil moisture, soil nutrient balance, microbial community structure and processes, hydrology and soil oxygen concentration in the models. We recommend that soil monitoring and modelling focus on linking processes of soil C stabilization with the functioning of soil microbiota.
... However, retaining large numbers of trees in all harvested compartments could lead to an increase in the area harvested to meet wood demands because the wood production per area will decrease as the number of trees retained increases (Yoshida et al., 2005;Santaniello et al., 2017). This could explain why a minimum retention amount in each harvested compartment has been proposed in previous studies, e. g., 5-10% and 10 snags/ha (Newton, 1994), and applied in practice to managed forests in many regions, e.g., northern Europe Kuuluvainen et al., 2019). ...
Article
The area of tree plantations has been expanding globally. While plantations generally support less biodiversity than natural forests, the habitat function of plantations can be enhanced by management. Retention forestry is a promising method to mitigate the negative impacts of harvesting on forest-dependent species through retaining some vital habitat structures for organisms. Bats are highly dependent on forests and have an important pest-control function; however, their response to retention forestry remains unknown. We surveyed bat activity at clear-cut sites, sites with dispersed broad-leaved tree retention (medium-level retention: 50 trees/ha, high-level retention: 100 trees/ha), and unharvested Todo fir (Abies sachalinensis) plantations in Hokkaido, northern Japan. We analyzed the effects of these treatments on genus richness and the activity of three groups preferring different degrees of habitat openness (cluttered-space species, open-space species, and edge species). Genus richness and the activity of cluttered-space species were higher at retention sites than at clear-cut sites. Similarly, the activity of edge species was higher at high-level retention sites than at clear-cut sites and comparable to that at unharvested plantations. Unexpectedly, the pattern of open-space species was similar to that of edge species. The increase in bat activity due to high-level retention was predicted to be 3.4 and 6.1 times that of medium-level retention for cluttered-space and edge species, respectively. Our results imply that dispersed broad-leaved tree retention in conifer plantations mitigates the negative impacts of harvesting on cluttered-space and edge species, and high-level retention is more effective. Thus, retaining large numbers of trees in a few harvested compartments and clear-cutting in others can be more effective for conserving bat activity than retaining a smaller number of trees in each of many compartments. For biodiversity conservation in plantation landscapes, it would be worthwhile to consider not only the common strategy of low retention in each of many harvested compartments but also a management strategy that retains many trees in a few compartments.
... The test pieces of TP-04, TP-05, TP-06, TP-07, TP-08, and TP-09 were manufactured assuming the material of laser-cut mashrabiya [43]. Table 3 shows the composition of each test piece manufactured with the difference between the different retention periods of raw materials and surface materials [44]. For the composition of the test piece, PVC sheet, F/F, and veneer were processed for LLT, MDF, and HB, each having a different retention period, respectively. ...
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Dubai has the reputation of a continuously growing city, with skyscrapers and mega residential projects. Many new residential projects with poor choices of material and ventilation have led to a faster rise in sick building syndrome (SBS) in Dubai than in any other country, and the IAQ (indoor air quality) has become more critical. Volatile organic compounds (VOCs) and formaldehyde (HCHO) affect the health of residents, producing the phenomenon known as SBS (sick building syndrome). It has been reported that wood materials used for furniture and wooden windows and doors are a significant source of indoor air pollution in new houses. This paper aims to identify the factor elements emitting harmful chemical substances, such as VOCs and HCHO, from wooden mashrabiya (traditional Arabic window) by examining the characteristics of the raw and surface materials through test pieces. As a methodology, a small chamber system was used to test the amount of hazardous chemicals generated for each test piece. For Total volatile organic compounds (TVOC) and HCHO, the blank concentration before the injection and the generation after seven days were measured. The results showed that to reduce TVOC, it is necessary to secure six months or more as a retention period for raw materials and surface materials. The longer the retention period, the smaller the TVOC emission amount. In the case of mashrabiya, an HCHO low-emitting adhesive and maintenance for one month or more are essential influencing factors. It was proven that using raw materials with a three-month or more retention period and surface materials with a one-month or more retention period is safe for indoor mashrabiya. This study is the first study in the Middle East to identify factors and characteristics that affect the emission of hazardous chemicals from wood composite materials, such as wood mashrabiya, that affect indoor air quality in residential projects in Dubai. It analyzes the correlation between emission levels and the retention period of raw and surface materials, in order to provide a new standard for indoor air pollutants.
... Baseline data show that old hard pine wood is a valuable habitat for epixylic lichens (Santaniello et al. 2017a). Modelling approaches include wood production, deadwood accumulation, and climate-related issues on carbon stocks and albedo (Santaniello et al. 2017b;Cherubini et al. 2018). ...
Article
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Retention approaches in forest management are today common in several North European countries, integrated into the clearcutting practice as a way to promote biodiversity and maintain ecosystem functions. Individual green trees and retention patches (tree groups) are retained at final harvest, and deadwood is left at site or created. Here, we review research on retention in Sweden, Finland, Norway, the Baltic States, and NW Russia, with special focus on biodiversity. Following the first publication in 1994, about 180 peer-reviewed articles have been published. We present results from a systematic search of the retention literature, separated into the following topics: buffer zones, retention patches, high stumps, other types of deadwood, European aspen Populus tremula, and cost-efficiency. Russian literature is synthesized separately since studies from this region have so far almost exclusively been published in the Russian language. Furthermore, we describe six ongoing large-scale, replicated experiments with varying retention levels, five in Finland and one in Sweden, and summarize their main results. Among main conclusions for practice from the literature and experiments are that retention patches as large as 0.5 ha and 10-m-wide buffers to watercourses are not enough to maintain pre-harvest species composition but survival of forest species is still larger than on conventional clearcuts. Deadwood on clearcuts may present important habitats to saproxylic species, including rare and red-listed ones and a prioritization of tree species per stand is recommended. We identify several important future research directions including switch of focus towards the landscape as well as the species population level. Surveys in parts of European Russia where retention has been unintentionally implemented already for a century would indicate possible future trajectories of biodiversity and their drivers in other regions of Northern Europe. A stronger link to ecological theory would help in study designs and in the formulation of predicted outcomes.
... Some silvicultural practices, such as partial harvesting [21] or the retention of riverine and remnant linear forests [22,23], maintain deadwood at the landscape scale [24]. However, the artificial supply of snags could also have positive effects on associated wildlife at the stand level [25][26][27]. ...
Article
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Standing deadwood is an important attribute of old-growth boreal forests and it provides essential microhabitats for deadwood-associated species. In managed boreal forests, short rotations tend to limit the amount and diversity of standing deadwood. This study evaluates if the anthropogenic supply of deadwood attributes through tree girdling or by providing nest boxes may favor deadwood-associated species. We studied the short-term response of saproxylic beetles, foraging woodpeckers, and secondary cavity users to snag and cavity supply in 50 to 70-year-old black spruce stands. In spring 2015, we girdled 8000 black spruce according to two spatial distributions (uniform and clustered), and we also installed 450 nest boxes of six different sizes at three distances from the forest edge. Using trunk window traps, we captured significantly more beetles in sites with girdled trees than in control sites in both 2015 and 2016. We also recorded a trend of a greater abundance of beetles in clusters of girdled trees than within uniformly distributed girdled trees. Trypodendron lineatum (Oliver) dominated beetle assemblages, representing 88.5% of all species in 2015 and 74.6% in 2016. The number of beetles captured was 7× higher in 2015 than in 2016. In contrast, we observed greater amounts of woodpecker foraging marks in fall 2016 than in either fall 2015 or spring 2016. Woodpeckers foraged significantly more in clusters of girdled trees than within uniformly distributed girdled trees. Woodpeckers' foraging mark presence was positively associated with the proportion of recent cuts at 1 km around the study sites. Five Boreal Chickadee (Poecile hudsonicus Forster) pairs used nest boxes and occupied smaller box sizes that were located away from the forest edge. Our study showed that structural enrichment can be effective in rapidly attracting deadwood-associated species within managed forest stands.
... Increasing retention results in higher amount and more diverse quality of CWD (Santaniello et al. 2016(Santaniello et al. , 2017b, and retention tree groups also add structural variation to managed forests (Kruys et al. 2013). The location (site type) and size (level of retention) of retention tree groups are important determinants of the muchneeded continuity of large-sized CWD for saproxylic species. ...
Article
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Intensive forest management has been applied in most Fennoscandian forests for a period of almost one felling rotation. This paradigm has produced even-aged and even-structured forests of different successional stages that cover about 90% of forest land. At the same time, wildfires have been nearly eliminated in most of the Fennoscandian nature. Consequently, hundreds of species are red-listed because of forest management. To support these species, forest management requires improvements. Variable retention forestry and habitat restoration have been suggested to mitigate negative effects of forest management on biodiversity, and these have been practiced to some extent during the past few decades. Here, we review experimental results on the effects of variable retention and two restoration measures (prescribed burning and artificial addition of coarse woody debris) on different species groups in Fennoscandia. Our key findings are as follows: (i) Many species respond positively to felling within a few years, apparently due to released and often ephemeral resources, such as fresh residue and stumps. Species associated with shady conditions are negatively impacted, but any retention supports many of these, and their species composition remains almost unaffected with 50–70% retention of the initial tree volume. (ii) These effects remain detectable for at least 10–30 years or, according to some studies, nearly 100 years, e.g., in polypore fungi. (iii) Initial effects of prescribed burning on most species groups (apart from pyrophiles) are negative, but within 10–15 years post-fire sites begin to support many rare and threatened deadwood-dependent species. Epiphytic lichens, however, remain negatively affected. (iv) Artificial addition of deadwood (mostly high stumps) supports a wide spectrum of deadwood-dependent species, but the species composition differs from that of naturally died trees. (v) Moisture and micro-habitat variation are crucial for forest species at harvested sites, at least in forests dominated by Norway spruce. We conclude that felling method as such is of little importance for threatened forest species, although retention mitigates many negative effects. These species require microclimatic continuity, and maintenance and active increase of legacies, such as deadwood of different qualities (species, downed/standing, snag/log/stump, decay stage), very old trees, and tree species mixtures.
... However, CCF resulted in a large increase in structural diversity compared to even-aged management, in particular through high proportions of old and mature broadleaf-rich forests, and a much higher density of large-diameter trees. In addition, retention patches clearly improved the conditions for biodiversity compared to even-aged management, which is in line with conclusions from observations and earlier simulations of retention patches [35,[66][67][68]. Our findings support earlier research that found that selection cutting and retention forestry increase the structural diversity, and thus provide for a better continuity of ecosystem functions of forests compared to evenaged forestry [20,36,42]. ...
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Research Highlights: We show the difference in the long-term effects on economic and ecological forest values between four forest management scenarios of a large representative forest landscape. The scenarios were largely formulated by stakeholders representing the main views on how to manage north-European forests. Background and Objectives: Views on how to balance forest management between wood production and biodiversity differ widely between different stakeholder groups. We aim to show the long-term consequences of stakeholder-defined management scenarios, in terms of ecological and economic forest values. Materials and Methods: We simulated management scenarios for a forest landscape in Sweden, based on the management objectives and strategies of key stakeholders. We specifically investigated the difference in economic forest values coupled to wood supply and ecological indicators coupled to structural biodiversity between the scenarios over a 100-year period. The indicators were net present value, harvest, growing stock and increment, along with deadwood volume, the density of large trees, area of old forests and mature broadleaf-rich forests. Results: We show that the scenarios have widely different outcomes in terms of the studied indicators, and that differences in indicator outcome were largely due to different distributions in management regimes, i.e., the proportion of forest left unmanaged or under even-aged management or continuous cover forest, as well as specific retention practices. Retention and continuous cover forestry mitigate the negative effects that clear-cut forestry has upon biodiversity. Conclusions: We found that an increase in the forest area under the continuous cover forestry regime could be a cost-efficient way to increase structural diversity in managed boreal forests. On the other hand, no single management regime performed best with respect to all indicators, which means that a mixture of several management regimes is needed to balance conflicting objectives. We also show that the trade-off between economic and ecological indicators was not directly proportional, meaning that an increase in structural biodiversity may be obtained at a proportionally low cost with appropriate management planning.
... Some silvicultural practices, such as partial harvesting (Santaniello et al. 2017) or retention of both live and dead large trees in riverine and remnant linear forests (Remm et al. 2006; can allow a relative intake of deadwood at the landscape scale (Moussaoui et al. 2016). Nevertheless, those techniques are not always implemented in management strategies due to several economic or logistical restrictions, thus leading to a possible local lack of old-growth forest attributes ). ...
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Ambient air pollution is the primary environmental health risk concern worldwide that causes seven million preventable deaths per year and the loss of healthy years of life; it threatens the sustaining of the environment through acidification and eutrophication. Almost all of the global population breathes air that exceeds the latest health-based guideline levels set by the World Health Organization, with low- and middle-income countries experiencing the highest exposure. Key sources of air pollution are road transport vehicles, domestic heating and industrial installations, and transboundary emissions. These sources produce the main ambient air pollutants of concern to which the population is exposed: particulate matter, ground-level ozone, nitrogen dioxide, carbon monoxide, and sulphur dioxide. Air quality models constitute a complementary approach to monitoring and characterising air pollution. Spatial and temporal variability of air pollution is mainly investigated across urban areas or those hosting industrial activities, especially in developed countries, where the highest concentration of air pollutants is expected. Understanding these spatial and temporal variabilities is essential for both the implementation of air quality policies and the definition of effective measures to mitigate air pollution and its effects. This Special Issue aims to showcase selected and original research articles concerning air quality characterisation and modelling. It includes 16 manuscripts covering a wide range of modelling topics, geographical scopes, and the characterisation of different fractions of air pollution. Among modelling approaches are emission inventories, simulation scenarios, dispersion models, source contribution techniques, and, more particularly, cluster analysis and linear and non-linear regressions, to cite a few. In some manuscripts, air quality indexes or coefficients are used to characterise air quality; others, such as the thermal sensation index or a particular decomposition of the Gini coefficient, are not as frequently used. The geographical scope was diverse, both in urban agglomerations and rural areas, with air quality studies in several countries. Among the studied facets of air pollution were outdoor and indoor pollution, thermal comfort, or the quantification of suspendable road dust. Other included studies examined the role of administrations in air quality, evaluating the effectiveness of local emission reduction plans or carbon trading policies. We hope the air quality characterisation and modelling community will find this special issue to be an informative and useful collection of articles and serve as an impetus to spur much more research on the topic.
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1. In a landscape consisting primarily of intensive forestry interspersed with some protected areas, multifunctional forestry with retention trees can play a crucial role in nature conservation. Accurate mapping of retention trees is important for guiding landscape-level conservation and forest management and improving landscape connectivity. Sizeable dead and living retention trees play a particularly important ecological role but even their large-scale inventory is often intensive through field work and/or inaccurate. We aimed to detect and classify retention trees using the novel nationwide Finnish airborne laser scanning (ALS) data (~5 pulses/m2) in conjunction with unrectified colour-infrared (CIR) aerial imagery. 2. Applying photogrammetric principles, we added spectral information from the CIR imagery to the ALS-derived point cloud. For a training dataset of 160 retention trees from 19 stands and a geographically separate validation dataset of 79 trees from eight stands, we segmented trees via individual tree detection (ITD), removed most trees belonging to the regenerating vegetation layer, and classified trees into living conifers, living broadleaves and dead trees by linear discriminant analysis. 3. The detection rate via ITD differed considerably for dead and living trees, with 41.7% of all dead and 83.8% of all living trees being detected with relatively low commission error rates. Dead trees with smaller diameters and heights were more likely missed, while grouping caused living tree omission. For classification into living conifers, living broadleaves and dead trees, an overall accuracy of 67.3% was achieved in training and 71.2% in validation using only ALS-derived metrics. When adding spectral metrics, the overall accuracies were 79.6% and 61.0% for training and validation respectively. 4. Our findings imply that wall-to-wall large-scale high density ALS data can be used to detect retention trees rather accurately—even larger dead trees—and that metrics derived solely from ALS data can accurately classify detected retention trees into living conifers, living broadleaves and dead trees. Considering the ecological value of retention trees, our results are promising and indicate that ALS data of the studied pulse density are a cost-effective option for large area mapping of retention trees in countries with such data available.
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Background Over the last 25 years, the prominent forest certification system established by the Forest Stewardship Council (FSC) has used by many companies worldwide for claiming responsible forest management. The objectives of the Russian National FSC standard to decrease the size of clearcuts and the retention of forest elements such as residual seed trees need on-site validation to proof the effectiveness of FSC. To assess the ecological impacts of harvesting practices and benefits of FSC certification, we geospatially compared logging activities with and without FSC certification. Within a sample area covering approximately 3,000 km ² in the east of the Russian Arkhangelsk Region, we used available data on tree cover loss and satellite images to assess secondary impacts of clearcuttings on adjacent remnant forests and to quantify the logging intensity. Additionally, the size and structure as well as the density of skidding trails of ten specific clearcuttings located within the sample area were surveyed using satellite images and in the field observation to delineate the boundaries of clearcuts and forested remnants within the clearcuts. Results We found a significant increase of small-scale tree cover loss in the proximity of the clearcuts. Patchy dieback is possibly linked to the scale and intensity of logging in the surroundings. On the investigated clearcuts, FSC failed to reduce the size, to increase the retention of forest remnants including seed trees on logged areas, and to maintain larger tracts of undisturbed ground and soil compared to clearcuts that were logged before they received FSC-certification. Conclusions Trees and forest remnants remaining inside an increasingly stressed forest ecosystem matrix may not resist further harvesting-related and climate change-induced stresses and disturbances. Large-scale clearcuttings seem to have negative impacts even in adjacent forests and undermine the ecological effectiveness of FSC certification in the study area. The Russian FSC standard is not clearly setting effective guidelines that induce a change in clearcutting practices in order to reduce ecological risks.
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Forests are widely recognized as major providers of ecosystem services, including timber, other forest products, recreation, regulation of water, soil and air quality, and climate change mitigation. Extensive tracts of boreal forests are actively managed for timber production, but actions aimed at increasing timber yields also affect other forest functions and services. Here, we present an overview of the environmental impacts of forest management from the perspective of ecosystem services. We show how prevailing forestry practices may have substantial but diverse effects on the various ecosystem services provided by boreal forests. Several aspects of these processes remain poorly known and warrant a greater role in future studies, including the role of community structure. Conflicts among different interests related to boreal forests are most likely to occur, but the concept of ecosystem services may provide a useful framework for identifying and resolving these conflicts.
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The performance of growth models implemented in the Swedish Forest Planning System Heureka was evaluated. Four basal area growth models were evaluated by comparing their predictions to data from five-year growth records for 1711 permanent sample plots of the National Forest Inventory (NFI-data). Also, two alternative implementations of Heureka, including a combined stand- and tree-level basal area growth model and a single tree-level model, respectively, were evaluated using data from 57 blocks in a thinning experiment (GG-data) involving Scots pine (Pinus sylvestris L.) and Norway spruce (Picea abies (L.) Karst) in which the trees were monitored for 30 years after the first thinning. The predicted volume growth was also compared to observed values. Growth models based on data from 1970's and 1980's overestimated growth in the NFI test plots from the early 2000's by about 3%. Stand-level models had larger precision than tree-level models. Basal area growth was underestimated in dense NFI-plots and overestimated in non-thinned GG-plots, illustrating an un-solved modelling problem. Basal area growth was overestimated by 2-5% also in the GG-plots over the whole observation period. Volume growth was however accurately predicted for pine and underestimated by 2% for spruce. The relative prediction error did not increase with increasing length of prediction period. Thinning response models calibrated with GG-data worked well in the total application and produced growth levels for different thinning alternatives in line with observations.
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The rotation length is a key component of even-aged forest management systems. Using Fennoscandian forestry as a case, we review the socioecological implications of modifying rotation lengths relative to current practice by evaluating effects on a range of ecosystem services and on biodiversity conservation. The effects of shortening rotations on provisioning services are expected to be mostly negative to neutral (e.g. production of wood, bilberries, reindeer forage), while those of extending rotations would be more varied. Shortening rotations may help limit damage by some of today’s major damaging agents (e.g. root rot, cambium-feeding insects), but may also increase other damage types (e.g. regeneration pests) and impede climate mitigation. Supporting (water, soil nutrients) and cultural (aesthetics, cultural heritage) ecosystem services would generally be affected negatively by shortened rotations and positively by extended rotations, as would most biodiversity indicators. Several effect modifiers, such as changes to thinning regimes, could alter these patterns.
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Kuuluvainen, T. & Aakala, T. 2011. Natural forest dynamics in boreal Fennoscandia: a review and classification. Silva Fennica 45(5): 823–841. The aim here was to review and summarize the findings of scientific studies concerning the types of forest dynamics which occur in natural forests (i.e. forests with negligible human impact) of boreal Fennoscandia. We conducted a systematic search for relevant studies from selected reference databases, using search terms describing the location, structure and proc-esses, and degree of naturalness of the forest. The studies resulting from these searches were supplemented with other known works that were not indexed in the databases. This procedure yielded a total of 43 studies. The studies were grouped into four types of forest dynamics according to the information presented on the characteristics of the native disturbance-succession cycle: 1) even-aged stand dynamics driven by stand-replacing disturbances, 2) cohort dynamics driven by partial disturbances, 3) patch dynamics driven by tree mortality at intermediate scales (> 200 m 2) and 4) gap dynamics driven by tree mortality at fine scales (< 200 m 2). All four dynamic types were reported from both spruce and pine dominated forests, but their commonness differed. Gap dynamics was most commonly reported in spruce forests, and cohort dynamics in pine forests. The studies reviewed provide the best obtainable overall picture of scientific findings concerning the characteristics and variability of the unmanaged boreal forest dynamics in Fennoscandia. The results demonstrate that the unmanaged Fennoscandian forests are characterized by more diverse and complex dynamics than has traditionally been acknowledged.
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Abstract: In Sweden, where forests cover more than 60% of the land area, silviculture and the use of forest products by industry and society play crucial roles in the national carbon balance. A scientific challenge is to understand how different forest management and wood use strategies can best contribute to climate change mitigation benefits. This study uses a set of models to analyze the effects of different forest management and wood use strategies in Sweden on carbon dioxide emissions and removals through 2105. If the present Swedish forest use strategy is continued, the long-term climate change mitigation benefit will correspond to more than 60 million tons of avoided or reduced emissions of carbon dioxide annually, compared to a scenario with similar consumption patterns in society but where non-renewable products are used instead of forest-based products. On average about 470 kg of carbon dioxide emissions are avoided for each cubic meter of biomass harvested, after accounting for carbon stock changes, substitution effects and all emissions related to forest management and industrial processes. Due to Sweden’s large export share of forest-based products, the climate change mitigation effect of Swedish forestry is larger abroad than within the country. The study also shows that silvicultural methods to increase forest biomass production can further reduce net carbon dioxide emissions by an additional 40 million tons of per year. Forestry’s contribution to climate change mitigation could be significantly increased if management of the boreal forest were oriented towards increased biomass production and if more wood were used to substitute fossil fuels and energy-intensive materials.
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To address the challenges of biodiversity conservation and commodity production, a framework has been proposed that distinguishes between the integration (“land sharing”) and separation (“land sparing”) of conservation and production. Controversy has arisen around this framework partly because many scholars have focused specifically on food production rather than more encompassing notions such as land scarcity or food security. Controversy further surrounds the practical value of partial trade-off analyses, the ways in which biodiversity should be quantified, and a series of scale effects that are not readily accounted for.We see key priorities for the future in (1) addressing these issues when using the existing framework, and (2) developing alternative, holistic ways to conceptualise challenges related to food, biodiversity, and land scarcity.
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Restoration by imitating natural disturbances is widely practised in boreal forests to increase the availability of habitats for specialized species. We studied the abundance and species richness of saproxylic beetles on different types of created dead wood during 2 years after restoration. The study was conducted on areas of a large-scale experiment in which Norway spruce (Picea abies (L.) Karst.) forests were restored by controlled burning and partial harvesting with down wood retention in southern Finland. More beetle species were attracted to spruces than to birches and more species were attracted to burnt trees than to unburnt trees killed by girdling. Birch-living species consistently benefited from fire, but on spruce, the abundance of cambium consumers and their associates was negatively affected by fire. Trees at harvested sites attracted more beetles in the first year, but the volume of down wood retention had only minor effects. Beetle assemblages were strongly altered by burning and harvesting. We conclude that burning and harvesting are efficient tools to promote species richness within a short time period, but there is a risk that the dead wood resource may be rapidly exhausted. Moreover, many saproxylic species of spruce forests may not be adapted to open habitats formed by stand-replacing disturbances.
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We investigated the transformation of a large (135 000 ha) forest landscape in boreal Sweden from the end of the 19th century to the end of the 20th century. Historical documents were used to obtain quantitative data on fire influence, historical logging, the development of forest management, and the ecological changes of the forest landscape over the last century. The imprint of the fire-regenerated preindustrial forest is still discernible in the present landscape, although very important ecological structures; e.g., old trees and multiple-storied stands, have been removed and fundamental processes, e.g., forest fire, have ceased. The 19th century boreal forest landscape was shaped by recurrent forest fires and was characterized by continuous multistoried old-growth forest, containing also a deciduous component that no longer exists. Our data indicate that many of the interpretations of previous natural landscape properties used as base-line conditions in forest management must be seriously questioned. Historical records and their limitations when used for reconstruction of forest stand structure are discussed.
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An increased use of wood products and an adequate management of forests can help to mitigate climate change. However, planning horizons and response time to changes in forest management are usually long and the respective GHG effects related to the use of wood depend on the availability of harvested wood. Therefore, an integral long-term strategic approach is required to formulate the most effective forest and wood management strategies for mitigating climate change.The greenhouse gas (GHG) dynamics related to the production, use and disposal of wood products are manifold and show a complex time pattern. On the one hand, wood products can be considered as a carbon pool, as is the forest itself. On the other hand, an increased use of wood can lead to the substitution of usually more energy-intense materials and to the substitution of fossil fuels when the thermal energy of wood is recovered. Country-specific import/export flows of wood products and their alternative products as well as their processing stage have to be considered if substitution effects are assessed on a national basis.We present an integral model-based approach to evaluate the GHG impacts of various forest management and wood use scenarios. Our approach allows us to analyse the complex temporal and spatial patterns of GHG emissions and removals including trade-offs of different forest management and wood use strategies. This study shows that the contributions of the forestry and timber sector to mitigate climate change can be optimized with the following key recommendations: (1) the maximum possible, sustainable increment should be generated in the forest, taking into account biodiversity conservation as well as the long-term preservation of soil quality and growth performance; (2) this increment should be harvested continuously; (3) the harvested wood should be processed in accordance with the principle of cascade use, i.e. first be used as a material as long as possible, preferably in structural components; (4) waste wood that is not suitable for further use should be used to generate energy. Political strategies to solely increase the use of wood as a biofuel cannot be considered efficient from a climate perspective; (5) forest management strategies to enhance carbon sinks in forests via reduced harvesting are not only ineffective because of a compensatory increase in fossil fuel consumption for the production of non-wooden products and thermal energy but also because of the Kyoto-“cap” that limits the accountability of GHG removals by sinks under Article 3.3 and 3.4, at least for the first commitment period; (6) the effect of substitution through the material and energy use of wood is more significant and sustained as compared with the stock effects in wood products, which tend towards new steady-state flow equilibria with no further increase of C stocks; (7) from a global perspective, the effect of material substitution exceeds that of energy recovery from wood. In the Swiss context, however, the energy recovery from wood generates a greater substitution effect than material substitution.
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Mathematical programming and computers have been used for several decades to solve complex and long term forest management planning problems. The ever increasing demand on the forest ecosystem to produce wood and other goods and services poses a corresponding demand on a forest decision support system. As a response to meet new requirements the development of the Heureka system was initiated at SLU in 2002 and a first version of the system was released in 2009. Based on a common kernel, a number of applications of the system for different problem areas and users have been developed. The three main applications are made up by an interactive stand simulator, a tool for long term forest level planning containing an optimization module, and a simulator for regional analyses. The system contains models for growth projections, simulation of treatments, estimation of recreation values and carbon sequestration, and habitat suitability. It is also possible to make projections under different climate scenarios. In addition the system includes a number of supporting applications for importing data from different sources, for field inventory, and for comparing and ranking alternative management plans. © 2011 Publisher of the Mathematical and Computational Forestry & Natural-Resource Sciences.
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The question of how to meet rising food demand at the least cost to biodiversity requires the evaluation of two contrasting alternatives: land sharing, which integrates both objectives on the same land; and land sparing, in which high-yield farming is combined with protecting natural habitats from conversion to agriculture. To test these alternatives, we compared crop yields and densities of bird and tree species across gradients of agricultural intensity in southwest Ghana and northern India. More species were negatively affected by agriculture than benefited from it, particularly among species with small global ranges. For both taxa in both countries, land sparing is a more promising strategy for minimizing negative impacts of food production, at both current and anticipated future levels of production.
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The terrestrial carbon sink has been large in recent decades, but its size and location remain uncertain. Using forest inventory data and long-term ecosystem carbon studies, we estimate a total forest sink of 2.4 ± 0.4 petagrams of carbon per year (Pg C year–1) globally for 1990 to 2007. We also estimate a source of 1.3 ± 0.7 Pg C year–1 from tropical land-use change, consisting of a gross tropical deforestation emission of 2.9 ± 0.5 Pg C year–1 partially compensated by a carbon sink in tropical forest regrowth of 1.6 ± 0.5 Pg C year–1. Together, the fluxes comprise a net global forest sink of 1.1 ± 0.8 Pg C year–1, with tropical estimates having the largest uncertainties. Our total forest sink estimate is equivalent in magnitude to the terrestrial sink deduced from fossil fuel emissions and land-use change sources minus ocean and atmospheric sinks.
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Anthropogenic GHG emissions add a fast reinforcing feedback cycle to global carbon dynamics which continues to influence GHG concentrations in the Earth’s atmosphere. When looking at forest carbon cycles there is potential in utilizing another feedback cycle, namely the carbon cycle involving harvested wood products. To assess the potential of the mitigation options arising from these carbon flows, the forest-based sector in Austria was modelled to assess causal links, dependencies and dynamics involved in GHG-relevant processes. Carbon dynamics were investigated in forests and forest soil carbon, the forest product chain and life-cycle analyses for substitution of conventional products with wood products in a cascade of different modelling approaches and paradigms, and the results synthesized. It was found that material use of products from domestic timber sources has the highest climate change mitigation efficiency when originating from sustainably managed forests regarding biomass stocks. The emissions saved through building up a carbon stock from harvested wood products and through emissions substitution can be as high as »20 years of total annual Austrian emissions in 90 years. Additional conservation measures while sustaining sawnwood production and the related GHG benefits at a high level had the highest contribution to an overall carbon sink.
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Green tree retention is often applied in forests otherwise harvested by clearcutting. Its aim is to support biodiversity by contributing to a continuity of living trees and large-diameter dead wood in the new generation of a forest. However, high levels of mortality can undermine the aims of tree retention and pose a concern for forest managers. Therefore, knowledge about the mortality of retention trees over the long term is needed. We calculated cumulative tree mortality for the seven most common tree species up to 20 years after clearcutting based on a chronosequence of dead and living trees in 583 tree groups on 206 clearcuts distributed over a wide area in boreal central Sweden. For all tree taxa combined and for the three most common tree taxa (Scots pine, Norway spruce and two birch species) we modeled tree mortality based on structural and environmental variables measured for each tree group and characteristics of the clearcut using generalized linear mixed effects models. The cumulative mortality averaged over all clearcut ages was 12% for Scots pine, 25% for Norway spruce and 16% for birch. Only 10% of all retention tree groups had a mortality >50%. Key factors reducing mortality for all tree taxa combined were tree density, tree volume of a retention group and the position at a former stand edge abutting open habitat, while a high wind exposure increased tree mortality. For the three most common species (pine, spruce, birch), the same factors as for all taxa combined were of importance, except tree density that resulted in species specific responses. For pine and spruce, the presence of seed trees on the clearcut reduced mortality. Increased mortality was additionally observed on wet soils. Mortality increased with tree height in birch and with diameter and slenderness ratio in spruce. Generally, a focus on retaining trees in groups with large tree volumes and tree density in less wind exposed positions and on forest edges will decrease the mortality after clearcutting and thus also reduce dead wood input.
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Tree stump harvesting could significantly increase the amount of bioenergy feedstock that forestry can supply to substitute for fossil alternatives. However, the climate mitigation potential of using stumps for bioenergy has been debated due to their often long residence time in the forest caused by slow decomposition. This study evaluated the climate effect over time of utilising stumps for bioenergy using ecosystem forest carbon modelling and time-dependent LCA methodology, including uncertainties in soil carbon changes. Different climate impact metrics were used (global mean temperature change, global warming potential and cumulative radiative forcing) and evaluations were made for single harvest as well as continuous supply over a landscape. Stump harvesting scenarios for spruce forests across Sweden were simulated and the forest net carbon balance was estimated as the difference compared with a reference scenario where the stumps were left to decompose in the forest.
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For efficient conservation, we need to consider both what kinds of habitat species require and the landscape-level supply of these habitats. We examined the relative importance of stand and dead wood types for wood-dependent lichens in two managed boreal forest landscapes in Sweden. We found 20 species and modelled their abundance based on stand type and dead wood characteristics using hierarchical Bayesian models or point estimates. Stands <60 years both have a large total extent and a large proportion of dead wood, resulting in the main part of the populations of most wood-dependent lichens occurring there. Older managed stands and unmanaged mires harbour smaller proportions of the populations. Stumps and snags, and to some extent logs, had high abundances of many species of wood-dependent lichens in managed forest landscapes, while dead branches were used by few species. Measures taken to produce more snags should benefit wood-dependent lichens in managed landscapes.
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Structural diversity of forests is important for biodiversity. In managed forests, structural diversity can be maintained by retaining living and dead trees, and by creating dead wood during logging operations. In Sweden, a small percentage of the trees is currently retained on each clear-cut. Since retention decreases revenues from forest harvesting, it is important to understand the consequences of retention for both forestry economy and biodiversity conservation. Thus, in this study we compared effects of retaining percentages ranging from 5% to 50% of the initial number of trees in 12 Scots pine-dominated stands in central Sweden. The retained trees in each stand consisted of equal proportions of green living trees, felled trees, high-cut trees and girdled trees. We estimated costs associated with tree retention and, as indicators of biodiversity conservation values, dead wood volumes, number of dead wood types, and dead wood diversity. We also estimated the damage caused by the logging operations on old dead wood. Revenue declined with increases in retention level, due mainly to associated reductions in harvested volumes, but partly to increases in logging costs. Both harvester and forwarder performance were lower at high than at low retention levels. The volume of dead wood increased with increases in retention level, since the number of retained trees killed per stand was proportional to the retention level. The number of dead wood types and dead wood diversity increased continuously up to the highest retention level of almost 50%. Moreover, old dead wood that was deemed particularly valuable for biodiversity was not destroyed at retention levels above 30%. In conclusion, dead wood destruction decreased with increasing retention level and costs increased proportionally to the retained volume. There were no signs of saturation of dead wood diversity as retention level increased. Therefore, mainly economic restrains will determine the retention level.
Article
The study presents a method to evaluate the response of forest ecosystems to increased biomass extraction based on the integrated ecosystem model ForSAFE. It evaluates the effects of residue removal, intensification of thinnings and a shorter rotation period on a forest site in Southern Sweden. The evaluation includes multiple ecosystem indicators for productivity, carbon storage, wood production, water use and water quality. Such integrated assessments can contribute to identify negative or positive impacts affecting ecosystem services provided by forests. Results show that increased biomass extraction reduces the carbon stored in the forests, but at the same time reduces the loss of nitrogen and carbon through leaching. Within one rotation, residue removal affects the carbon stock in the soil, but it does not affect forest productivity and therefore tree carbon stock. Contrarily, the intensification of thinnings and shorter rotation periods reduce carbon stored in trees. In all cases, the amount of wood available for products increases, but the additional harvest from increased thinnings and earlier clear cutting does not compensate for the loss of carbon in trees. A positive consequence of removing the decomposing material from the site is the reduced amount of nutrients lost with runoff. Both leached nitrogen and dissolved organic carbon decrease with intensification. In addition, a positive effect of increased thinnings and a shorter rotation period is a reduced evapotranspiration, i.e. reduced water use. The effect on acidification differed depending on the time frame considered and the applied management scenario, due to different dominating processes regulating acidity. To avoid acidification, management intensification should include measures to prevent loss of base cations in the soil. Overall, under the studied conditions, the risk for negative effects seems to be smaller for residue extraction than for management changes including additional tree harvest.
Article
Aim Restoration of habitats may be used as a conservation tool when ecosystems have lost their natural structure, dynamics or functioning over large areas. Controlled and planned use of fire could be an effective way to restore habitats of many threatened species in boreal forests where fire suppression has been effective. We asked whether the large‐scale landscape context affects the occurrence of rare and threatened species in forest habitats that have been burned to restore their fire‐related structures. Location Boreal forests in southern Finland. Methods We designed a large‐scale field experiment that included nine Pinus sylvestris forests (5–10 ha each) in southern Finland. Sites were located in two regions: (1) in eastern region with shorter management history and (2) in western region where intensive forestry has continued longer. We evaluated whether restoration of dead/burned wood is beneficial for rare and conservation‐dependent species and measured the recovery of pyrophilous and red‐listed insects (beetles and flatbugs) in burned forests, using standardized sampling effort. Altogether, 956 individuals of 29 red‐listed and pyrophilous species were sampled. Results Rare species colonized areas quickly, but there was a clear difference in species richness between the regions. The eastern forests harboured higher species richness after restoration. In these sites, the average species richness was 13.7 species per site, whereas in western forests it was 5.0 species per site. Similar pattern was also observed in subgroups: the corresponding numbers for pyrophilous species were 9.7 vs. 3.8, for red‐listed 8.7 vs. 2.3 and for red‐listed pyrophiles 4.7 vs. 1.2. Main conclusions Introducing fire back to boreal forests can aid in the recovery of rare species, but the landscape context considerably affects the success of restoring species. If restored habitats are located in landscapes that have lost their natural properties long ago, the success of restoration seems to be more challenging than in landscapes where habitats have been modified more recently.
Article
A conservative estimate for the total number of species dependent on dead-wood habitats is 4000-5000 within the area of Finland, which accounts for 20-25% of all forest-dwelling species. A large body of data concerning the average amounts of coarse woody debris (CWD) in both natural and managed forests has accumulated during the 1990s in Fennoscandia, including results from national forest inventories. The average volume of CWD in old-growth forests is generally 60-90 m³ ha1\text{ha}^{-1} in southern Fennoscandia, and declines to 20 m³ ha1\text{ha}^{-1} close to the timberline. Available data and modelling results indicate that the volume is even much higher following disturbance, and only slightly lower in mature natural forests. In managed forest landscapes the average volumes vary between 2 and 10 m³ ha1\text{ha}^{-1} depending on the region. This means that the average amount of CWD at the landscape level has probably been reduced by 90-98%. General species-area relationships suggest that such a reduction in available habitat might lead to the disappearance of &gt 50% of original saproxylic species in managed forests in the long term. Several recent studies have shown that the number of saproxylic species per stand depends on the amount of CWD, and also on the average size and decay stage of dead trunks. These relationships can be explained by either higher habitat diversity (more different niches) or larger population sizes of individual species (lower risk for local extinction) with increasing amount of CWD. A third important factor explaining local species richness of species living in ephemeral habitat patches, i.e. dead trees that decay away, is the spatiotemporal continuity of suitable host trees. Important theoretical and practical issues for conservation, management and research include, for instance, how well the remaining high-quality patches (e.g. old-growth fragments, key habitats) can secure the regional persistence of saproxylic species, and how much, what kind, and where CWD should be retained in the ordinary managed forests in order to maintain most of the species.
Article
Selective logging is a major driver of rainforest degradation across the tropics. Two competing logging strategies are proposed to meet timber demands with the least impact on biodiversity: land-sharing, which combines timber extraction with biodiversity protection across the concession; and land-sparing, in which higher-intensity logging is combined with the protection of intact primary forest reserves. We evaluate these strategies by comparing the abundances and species richness of birds, dung beetles and ants in Borneo, using a protocol that allows us to control for both timber yield and net profit across strategies. Within each taxonomic group, more species had higher abundances with land-sparing than land-sharing logging, and this translated into significantly higher species richness within land-sparing concessions. Our results are similar when focusing only on species found in primary forest and restricted in range to Sundaland, and they are independent of the scale of sampling. For each taxonomic group, land-sparing logging was the most promising strategy for maximizing the biological value of logging operations. This article is protected by copyright. All rights reserved.
Article
Vegetated riparian buffers are critical for protecting aquatic and terrestrial processes and habitats in southern Appalachian ecosystems. In this case study, we examined the effect of riparian buffer width on stream water quality following upland forest management activities in four headwater catchments. Three riparian buffer widths were delineated prior to cutting; 0m (no-buffer), 10m, and 30m, and one reference site (REF). A two-age prescription timber harvest was conducted on all cut sites with a target residual basal area of approximately 4.0m2ha−1. Harvesting occurred from October 2005 through February 2007. Stream sampling was conducted weekly from January 2004 through December 2008. Stream water chemistry, temperature, and total suspended solids (TSS) were used as metrics of water quality. Analyses were conducted on weekly grab samples. Pre-treatment concentrations of all solutes were similar to conditions found in other headwater streams at similar topographic positions around the region. The greatest responses to cutting occurred on the no-buffer site. Compared with pre-harvest levels on the no-buffer site, stream nitrate concentration ([NO3–N]) increased 2-fold during both base and stormflow following harvest, and all base cations increased in concentration. [NO3–N] on the no-buffer site showed steady decline with time following the initial post-harvest increase. The other sites did not show increases in [NO3–N] and very small or no responses in other stream chemistry parameters. There was no TSS response at stormflow on any site, and during baseflow, TSS decreased on all but the no-buffer site. Stream water temperature increased during the summer on the no-buffer site. Although alternative land uses may have different requirements, these results suggest that for riparian buffer widths of 10m and wider, the forest harvest activities implemented in this study did not substantially impact stream water quality. Hence, 10m wide buffers in these ecosystems may provide effective protection with respect to stream water chemistry, TSS, and temperature.
Article
As a result of legislation and forest certification schemes, retention of dead and live trees has become common in forest management. This study investigated the effect of retained Scots pines ( Pinus sylvestris L.) on production and field vegetation in the new stand. Stem volume per hectare and field vegetation composition at different distances from retained trees were examined for 60 trees on 25 sites at latitudes 55–68°?N. The mean ages of the new stands were 30–90?years. The volume of the new stand was reduced within 5–10?m from retained trees. Site fertility, as expressed by the field vegetation, had a large impact on the reduction. The loss of production in the new stand with 10 evenly dispersed retained trees per hectare was estimated at 3.0% on average pine sites and varied in an interval from 1.6 to more than 10% depending on site fertility. The loss was not significantly influenced by the size and growth of retained trees or development stage of the new stand. In the field vegetation, species indicating poor soil conditions were more common close to retained trees, while species demanding higher fertility were less common.
Article
Habitats of saproxylic species (species that are dependent on decaying wood) have been greatly changed during the last few decades. Due to intensive forest management, volume of dead wood has decreased and its quality is less diverse in managed than in naturally disturbed forests. There is an urgent need to develop and apply guidelines for forest management so that they also facilitate the survival of saproxylic species and mimic the natural dynamics of forests. This requires detailed information about how the differences in forest structure between managed and natural forests affect the occurrence of species and what are the real habitat requirements of species. Thus, we explored the richness of saproxylic beetles, composition of species assemblages and relationship between saproxylic beetles and their substrate in managed and seminatural pine dominated forests. Richness of saproxylic species tended to be higher in seminatural than in managed forests but the difference was not statistically significant. However, species assemblages in managed forests had differentiated from those on seminatural sites. Our results suggest that for the survival of saproxylic beetles, increasing the total volume of dead wood is an important task but more important one is to improve the diversity and continuity of dead wood in managed forests. This requires that the continuous production of dead wood is allowed also in managed forests to improve the continuity of dead wood and availability of recently dead wood. In green tree retention the main stress should be laid on the trees of large diameter to maintain the potential for large decaying wood.
Article
The host-tree and habitat requirements of an endangered saproxylic beetle species, Pytho kolwensis, which inhabits fallen spruce (Picea abies) trunks were studied. Host-tree quality of 150 potential host trees, 60 of which were inhabited, and stand characteristics were measured at six sites in eastern Finland. All of the P. kolwensis habitats were virgin spruce-mire forests with a stand continuity of at least 170–300 years, and a high volume of dead wood (73–111 m3/ha). Decay-class distribution of large-diameter logs was very even, indicating that the recruitment rate of large, fallen trunks had remained nearly constant for at least 100 years. Microclimate and host-tree quality were not likely factors explaining the habitat confinement of the species. We suggest that P. kolwensis is mainly restricted to spruce-mire forests because of the long-term continuous availability of suitable host trees in these habitats.
Article
Accurate estimates of below-ground biomass of trees are important when quantifying the amount of carbon sequestered in forests. Allometric single-tree below-ground biomass functions were developed for Pinus sylvestris , Picea abies and Betula pendula and Betula pubescens in Sweden. The idea was to calibrate an existing comprehensive data set of about 600 trees that only covered the stump and coarse roots against a new data set that covered roots down to 2?mm diameter. The new data set consisted of about 80 trees acquired using the same design as for the existing set, but complemented with a detailed inventory of the fine root fractions remaining in the ground. Checks were made to determine whether the density properties of the two data sets were comparable and it was concluded that they were. This was a prerequisite for calibrating the older data against the new information and further for merging the two data sets. The merged data set was used to derive regression functions for below-ground biomass. For all functions the adjusted R 2 values were always higher than 0.95 and the root mean square errors were always lower than 36% for P. sylvestris and P. abies . Below-ground biomass predicted with the new functions was approximately 11% higher than the values obtained using the existing biomass functions.
Article
We studied the immediate effects of retention-felling on the occurrence of tree uprooting in two different types of boreal spruce forest in Finland to determine whether susceptibility to uprooting is dependent on the biotope. During the first post-treatment year, 7.1% of the trees in the paludified forest type and 1.8% in the upland forest type were uprooted. During the 2 following post-treatment years, uprooting percentages increased considerably (39.3% in the paludified type and 11.5% in the upland type in year 2; 48.3% in the paludified type and 15.2% in the upland type in year 3). Norway spruce (Picea abies (L.) Karst.), the dominant species in both forest types, was the species most susceptible to uprooting. The high uprooting rate in the paludified groups was probably caused by an interaction between the rocky ground and moist overlying peat layer with the shallow root system of P. abies. As paludified forest biotopes are generally recognized to have high biodiversity, the use of green-tree retention in these biotypes may enhance the continuum and survival of sensitive species. Moreover, because of the high level of uprooting, green-tree retention in paludified forest types can quickly and more naturally help restore levels of coarse woody debris.
Article
The majority of the world's forests are used for multiple purposes, which often include the potentially conflicting goals of timber production and biodiversity conservation. A scientifically validated management approach that can reduce such conflicts is retention forestry, an approach modeled on natural processes, which emerged in the last 25 years as an alternative to clearcutting. A portion of the original stand is left unlogged to maintain the continuity of structural and compositional diversity. We detail retention forestry's ecological role, review its current practices, and summarize the large research base on the subject. Retention forestry is applicable to all forest biomes, complements conservation in reserves, and represents bottom-up conservation through forest manager involvement. A research challenge is to identify thresholds for retention amounts to achieve desired outcomes. We define key issues for future development and link retention forestry with land-zoning allocation at various scales, expanding its uses to forest restoration and the management of uneven-age forests.
Article
A new system is presented for predicting tree mortality, in order to improve Swedish long-term forest planning. A three-step approach was used, which consists of (I) estimating the probability of mortality on a sample plot; (II) quantifying the mortality in terms of proportion of basal area; and (III) distributing the mortality among individual trees. The system predicts the mortality for 5 yr periods. Data from permanent sample plots of the Swedish National Forest Inventory were used. Independent variables used for steps I and II were specific to site, stand and plot characteristics. In the step III models, which were tree-species specific, competition indices were also included. Logistic regression was used for steps I and III models, while linear regression was used for the step II models. A fair performance of the functions was observed, although mortality is a highly stochastic process. In applications, random simulation in all steps can mimic this.
Article
Many theoretical models have been proposed to explain the empirical self‐thinning relationship given by Yoda et al . in 1963 for even‐aged, monospecific stands of plants, but the models are inadequate to allow consensus on the processes driving variation in density‐dependent mortality and self‐thinning. Most non‐individual based models (non‐IBMs), and many IBMs, employ a common representation of competition in which a finite amount of potential crown area remains completely allocated throughout self‐thinning, making stand density inversely proportional to mean projected crown area. This representation entails four assumptions regarding the competition process: the population is adequately represented by the mean plant; total stand resource utilization is constant throughout self‐thinning; competition is a horizontal packing process; and differences in initial stand conditions may affect the rate of competition but not the process itself. Reviewing published empirical data, the competition literature and the logical implications for the self‐thinning process shows that all four assumptions are untenable as generalizations. Unfortunately, their application provides neither a mortality‐inducing mechanism nor insight into the relationship between stand growth and mortality. Explaining the observed variation in self‐thinning relationships therefore requires improved representation of the competition process. This improvement is likely to require IBMs that explicitly represent variation in plant size or resource acquisition, two‐dimensional stand distribution, dynamic rather than static stand resource utilization, and, perhaps, explicit three‐dimensional stand development. Most importantly, the requirement for explicitly modelling mortality mechanisms implies that whole plant models may be insufficient for insight into the self‐thinning process. The review reinforces the need to assess mechanistic models for more than their ability to reproduce a single, high‐level pattern. Such models should be assessed for their ability to simultaneously reproduce multiple features selected from the levels of both the modelled mechanisms and the high‐level patterns. Progress in understanding the observed variation in self‐thinning currently requires a shift from searching for universal insight into the modelling of specific mechanisms for specific plant types, eventually leading to a broader theory explaining how variation in plants affects the competition process.
Article
The literature on soil C change with forest harvesting, cultivation, site preparation, burning, fertilization, N fixation, and species change is reviewed. No general trend toward lower soil C with forest harvesting was apparent, unless harvesting is followed by intense burning or cultivation. Most studies show no significant change ( 10%) with harvesting only, a few studies show large net losses, and a few studies show a net gain following harvesting. Cultivation, on the other hand, results in a large (up to 50%) loss in soil C in most (but not all) cases. Low-intensity rescribed fire usually results in little change in soil C, but intense presribed fire or wildfire can result in a large loss of soil C. Species change can have either no effect or large effects on soil C, depending primarily upon rooting patterns. Fertilization and (especially) nitrogen fixation cause increases in soil C in the majority of cases, and represent an opportunity for sequestering soil C and causing long-term improvements in site fertility.
Article
Species-specific densities of saproxylic beetles in cut 4-m high, medium to large diameter stumps of spruce, birch, aspen and oak were monitored for 7years after cutting, by trapping emerging insects within seasonally applied net enclosures. A total of 47,038 individuals, representing 316 saproxylic beetle species including 40 red-listed species, were recorded. Densities of 86 species were modelled in relation to stump diameter and measured levels of sun-exposure. Two thirds of the species favoured semi- or fully exposed substrates, while one third performed better in shade. Few species seemed to be specifically adapted to semi-exposed conditions. Diameter was generally of less importance than exposure, and similar numbers of species favoured medium and large diameter substrates. Group mean diameter and exposure calculated from means per individual and species were similar for groups of modelled and non-modelled species, and for groups of red-listed and non-red-listed species, respectively. This indicates that the proportions found in the models are representative for the diverse regional fauna of saproxylic beetles that utilise high stumps of spruce, birch, aspen and oak in early stages of decay. The results suggest that sun-exposed dead wood substrates generated and retained in managed forest landscapes are potentially important for many species. However, stands of unmanaged self-thinning successions of deciduous trees, as well as substantial areas of old-growth spruce-forests are also necessary to address the wide spectrum of saproxylic beetles.
Article
In the future, a significant proportion of Northern forests may become intensively managed through the planting of monospecific stands of native or introduced trees, and the use of multiple silvicultural treatments such as forest fertilization. Such an intensification of management in selected parts of the landscape is suggested by different zoning models, for example the Triad approach, which is under evaluation in some regions of North America. In this study, based on Fennoscandian conditions, we predicted landscape-scale extinction risks of five hypothetical model insect species dependent on fresh dead wood from Norway spruce (Picea abies), by simulating colonizations and local extinctions in forest stands. Intensified forestry applied to 50% of the spruce stands led to strongly increased extinction risks of all species during the following 150years. For one species—the sun-exposure specialist—there were strong effects already after 50years. The negative effects of intensive plantation forestry could be compensated for by taking greater biodiversity conservation measures in other managed forests or by setting aside more forests. This is consistent with the Triad model, which is according to our analyzes an effective way to decrease extinction risks, especially for the short-dispersing species and the species associated with closed forest. A zoning of forest land into intensive forestry, conventional forestry, and set asides may be better at combining increased timber production and maintenance of biodiversity in comparison to landscapes where all production forests are managed in the same way. KeywordsCWD–Functional zoning–Metapopulation–Plantation forestry–Population viability analysis–Saproxylic insects–Triad
Article
Forest and bioenergy strategies offer the prospect of reduced CO2 emissions to the atmosphere. Such strategies can affect the net flux of carbon to the atmosphere through 4 mechanisms: storage of C in the biosphere; storage of C in forest products; use of biofuels to displace fossil-fuel use; use of wood products which often displaces other products that require more fossil fuel for their production. We use the mathematical model GORCAM (Graz/Oak Ridge Carbon Accounting Model) to examine these mechanisms for 16 land-use scenarios. Over long time intervals the amount of C stored in the biosphere and in forest products reaches a steady state and continuing mitigation of C emissions depends on the extent to which fossil fuel use is displaced by the use of bioenergy and wood products. The relative effectiveness of alternative forest and bioenergy strategies and their impact on net C emissions strongly depend, for example, on the productivity of the site, its current usage, and the efficiency with which the harvest is used. When growth rates are high and harvest is used efficiently, the dominant opportunity for net reduction in C emissions is seen to be fossil-fuel displacement. At the growth rates and efficiencies of harvest utilization adopted in many of our base scenarios, the net C balance at the end of 100 years is very similar whether trees are harvested and used for energy and traditional forest products, or reforestation and forest protection strategies are implemented. The C balance on a plantation system that provides a constant output of biomass products can look different than the balance of a single parcel of land.
Article
Green-tree retention cutting (GTR) is a modification of traditional clear-cutting, aimed at better consideration of biodiversity. We reviewed 214 North American and European studies to answer whether, and under which circumstances, GTR meets its objectives: ‘lifeboats’ species over the regeneration phase, provides microhabitats for old-forest species in re-established forest stands and for disturbance-phase species on the recent cuts, and enhances species’ dispersal by increasing landscape connectivity. To answer these questions is complicated, partly because the target taxa differ regionally and due to research biases: 81% of the studies have been carried out in North America, 82% have been short term, and the objective of improving landscape connectivity has not been studied. A meta-analysis of GTR effects on species richness and abundance of different taxa indicated no negative responses, but birds and ectomycorrhizal fungi benefited most. Compared with clear-cutting, GTR lowered the harvest-related loss of populations or individuals in 72% of studies, and it nearly always improved the habitat for disturbance-phase insects and birds on the cuts and for forest species in the regenerated stand. Lifeboating was most successful for ectomycorrhizal fungi, epiphytic lichens and small ground-dwelling animals, and least successful for bryophytes and vascular plants. Retention tree species always contributed to the success of GTR, followed by tree density (65% of cases) and the spatial arrangement of the trees (50%); the influence of forest type is likely, but insufficiently studied. Ectomycorrhizal fungi, epiphytes, birds, and wood-dependent beetles may be suitable indicator taxa for measuring the success of GTR. For future research, we encourage clearly objective oriented studies of relevant taxa, spatially explicit landscape perspectives, and long-term (including retrospective) studies.
Article
Elongation of rotation length is a forest management activity countries may choose to apply under Article 3.4 of the Kyoto Protocol to help them meet their commitments for reduction of greenhouse gas emissions. We used the CO2FIX model to analyze how the carbon stocks of trees, soil and wood products depend on rotation length in different European forests. Results predicted that the carbon stock of trees increased in each forest when rotation length was increased, but the carbon stock of soil decreased slightly in German and Finnish Scots pine forests; the carbon stock of wood products also decreased slightly in cases other than the Sitka spruce forest in UK. To estimate the efficiency of increasing rotation length as an Article 3.4 activity, we looked at changes in the carbon stock of trees resulting from a 20-year increase in current rotation lengths. To achieve the largest eligible carbon sink mentioned in Article 3.4 of the Kyoto Protocol, the rotation lengths need to be increased on areas varying from 0.3 to 5.1 Mha depending on the forest. This would in some forests cause 1–6% declines in harvesting possibilities. The possible decreases in the carbon stock of soil indicate that reporting the changes in the carbon stocks of forests under Article 3.4 may require measuring soil carbon.
Article
Temperate forests are an important carbon sink, yet there is debate regarding the net effect of forest management practices on carbon storage. Few studies have investigated the effects of different silvicultural systems on forest carbon stocks, and the relative strength of in situ forest carbon versus wood products pools remains in question. Our research describes (1) the impact of harvesting frequency and proportion of post-harvest structural retention on carbon storage in northern hardwood-conifer forests, and (2) tests the significance of including harvested wood products in carbon accounting at the stand scale. We stratified Forest Inventory and Analysis (FIA) plots to control for environmental, forest structural and compositional variables, resulting in 32 FIA plots distributed throughout the northeastern U.S. We used the USDA Forest Service's Forest Vegetation Simulator to project stand development over a 160 year period under nine different forest management scenarios. Simulated treatments represented a gradient of increasing structural retention and decreasing harvesting frequencies, including a “no harvest” scenario. The simulations incorporated carbon flux between aboveground forest biomass (dead and live pools) and harvested wood products. Mean carbon storage over the simulation period was calculated for each silvicultural scenario. We investigated tradeoffs among scenarios using a factorial treatment design and two-way ANOVA. Mean carbon sequestration was significantly (α = 0.05) greater for “no management” compared to any of the active management scenarios. Of the harvest treatments, those favoring high levels of structural retention and decreased harvesting frequency stored the greatest amounts of carbon. Classification and regression tree analysis showed that management scenario was the strongest predictor of total carbon storage, though site-specific variables were important secondary predictors. In order to isolate the effect of in situ forest carbon storage and harvested wood products, we did not include the emissions benefits associated with substituting wood fiber for other construction materials or energy sources. Modeling results from this study show that harvesting frequency and structural retention significantly affect mean carbon storage. Our results illustrate the importance of both post-harvest forest structure and harvesting frequency in carbon storage, and are valuable to land owners interested in managing forests for carbon sequestration.
Article
Many indicators and criteria have been proposed to assess the sustainable management of forests but their scientific validity remains uncertain. Because the effects of forest disturbances (such as logging) are often specific to particular species, sites, landscapes, regions and forest types, management “shortcuts” such as indicator species, focal species and threshold levels of vegetation cover may be of limited generic value. We propose an alternative approach based on a set of five guiding principles for biodiversity conservation that are broadly applicable to any forested area: (1) the maintenance of connectivity; (2) the maintenance of landscape heterogeneity; (3) the maintenance of stand structural complexity; and (4) the maintenance of aquatic ecosystem integrity; (5) the use of natural disturbance regimes to guide human disturbance regimes.
Article
The anticipated increasing utilisation of forest biomass necessitates improved understanding of its long-term consequences on forest productivity. We have used a model of carbon and nitrogen fluxes to predict effects of different management regimes in Norway spruce stands at three levels of fertility. Stands with high production are the least sensitive to intensified harvesting, partly because these stands occur in regions with high nitrogen deposition which compensates for the removal in nitrogen in harvests. Intensified thinning with stem-only removal is the management that affects productivity least followed by whole-tree harvesting at clear-fellings. Whole-tree thinnings are less beneficial and shortened rotation times the least desirable from a production point of view. Increases in total biomass harvests are at the expense of stem harvest, which can mean a conflict between volume and value. The importance of secondary vegetation as is also discussed.
Article
The overall aim of the studies underlying this thesis has been to qualify and quantify the regeneration of tree species in a range of typical growing environments of possible Continuous Cover Forestry (CCF) silvicultural systems in boreal forests of northern Sweden. Data presented in Papers I and II show that the light environment did not differ significantly between points at different distances to trees, but it was clearly affected by the stand stem density (SSD). On a north-facing slope, the emergence rates of direct-seeded seedlings were highest (50 and 44% of germinable Pinus sylvestris and Pices abies seeds, respectively) in a stand with an SSD of 150. In contrast, on a slope with a southern aspect the conditions in SSD 0 favoured emergence of P.sylvestris (41%). For planted P. abies, fertilised seedlings in SSD 0 grew the most (22.2 cm in height on the North and 34.2 cm on the South slope). Establishment of both P. sylvestris and P.abies seedlings was more controlled by the general (light) conditions of the stand than their orientation and distance with respect to the nearest tree. In Paper III, seedling survival and growth were compared between a clear-cut, a multi-layered shelterwood (MLS), and a single-layered shelterwood (SLS). The needle and root biomass of seedlings of both species, growing in identical (good) soil conditions, was highest in the clear-cut (P. sylvestris 63 and 14 g, respectively; P. abies 34 and 12 g, respectively). With those soil conditions, there were also no significant differences in growth, at least for P.sylvestris, between the MLS and SLS, although with increased belowground competition seedlings grew more slowly in the MLS. In Papers IV and V, the establishment and growth of Betula pendula, Populus tremula, P. sylvestris, Larix sibirica, Abies lasiocarpa, and P. abies, planted in a Chequered-Gap- Shelterwood-System (CGSS) with 0.135 ha gaps under a shelter of pine forest, were compared in a 30-year-old (“younger”) stand and a 50-year-old (“older”) stand. Solar radiation transmission in the CGSS was simulated by modelling, and the results of the model were further related to seedling height growth by seedling positions within gaps. In the older stand, it was more favourable for seedlings to grow in south-facing parts of a gap with higher transmission. An approach for estimating biomass based on image inventories was applied, which showed that seedlings generally developed more biomass during the study period in gaps than at edges and in the forest (586.4±93.5 versus 203.8±22.3 and 121.3±24.1 cm² silhouette areas, respectively, in the older stand for example). To conclude, the results from this thesis have shown that tree regeneration and early growth can be maximized in a CCF system by matching growth environments and species, based especially on the considered species’ light tolerance. Det övergripandet syftet med de fem studier som denna avhandling baseras på, har varit att ta fram mer kunskap om hur olika faktorer påverkar vid skogsföryngring i kontinuitetsskogsbruk i boreal skog i norra Sverige. Studie I och II, i grandominerade bestånd, visade att ljusmiljön inte skiljde sig signifikant mellan olika avstånd till skärmträd, men var klart påverkad av beståndets stamtäthet (hygge med 0, skärmställning med 150 eller orörd skog med 500 stammar per hektar). På en nordlig sluttning var plantbildningen störst, 50 och 44% av grobara frön av Pinus sylvestris (tall) respektive Pices abies (gran), i skärmställningen medan förhållandena på hygge var de mest gynnsamma för plantbildning av tall (41%) på en sydlig sluttning. Av planterade granar växte gödslade plantor på hygge mest (22.2 cm i höjd på den nordliga sluttningen respektive 34.2 cm på den sydliga), medan gödsling inte kunde påskynda tillväxt av plantor med sämre ljustillgång. Beståndstyp hade större betydelse för etablering av både tall- och gran plantor, i enlighet med ljusmiljön, än plantornas individuella placering i förhållande till närmaste skärmträd. I Studie III jämfördes plantöverlevnad och -tillväxt mellan ett hygge, en skiktad och en hög skärmställning. Båda arternas barr- och rotbiomassa var högst på hygget när de växte i likvärdig jord med god näringsstatus (63 respektive 14 g för tall och 34 respektive 12 g för gran). Med de markförhållandena var det inte heller någon signifikant skillnad i tillväxt, åtminstone för tall, mellan de olika skärmställningarna, medan ökad rotkonkurrens innebar att plantorna växte långsammare i den flerskiktade skärmställningen. I Studie IV och V jämfördes etablering och tillväxt av Betula pendula, Populus tremula, P. sylvestris, Larix sibirica, Abies lasiocarpa och P. abies, som planterats i 0.135 ha stora luckor bildande ett schackrutigt huggningsmönster (så kallat ”Chequered- Gap-Shelterwood-System”; CGSS) i ett 30-årigt (”yngre”) samt 50-årigt (”äldre”) tallbestånd. Transmissionen av solstrålning i CGS-systemet simulerades med hjälp av en modell, och resultaten från modellen relaterades sedan till position och höjdtillväxt hos planterade plantor i luckorna. I det äldre beståndet var det mer gynnsamt för plantorna att växa i luckornas nordliga delar (de som vetter mot söder) med högre transmission. En metod att skatta biomassa baserad på bildanalys användes, vilket visade att plantorna under perioden för studien generellt utvecklade mer biomassa i luckorna än vid beståndskanterna eller i skogen (586.4±93.5 mot 203.8±22.3 respektive 121.3±24.1 cm2 silhuettarea, med det äldre beståndet som exempel). Avhandlingens resultat visar sammanfattningsvis att föryngring och tidig tillväxt av trädarter i skötselsystem inom kontinuitetsskogsbruk kan optimeras med rätt kombination av miljö och art, med artens ljustolerans som främsta urvalskriterium.
Article
A chronosequence of three species of logs (Pinus sylvestris L., Picea abies (L.) Karst, and Betula pendula Roth.) from northwestern Russia was resampled to develop a new method to estimate rates of biomass, volume, and density loss. We call this resampling of a chronosequence the decomposition-vector method, and it represents a hybrid between the chronosequence and time-series approaches. The decomposition-vector method with a 3-year resampling interval gave decomposition rates statistically similar to those of the one-time chronosequence method. This indicated that, for most cases, a negative exponential pattern of biomass, volume, and density loss occurred. In the case of biomass loss of P. sylvestris, however, polynomial regression indicated decomposition rates were initially low, then increased, and then decreased as biomass was lost. This strongly suggests three distinct phases: the first when decomposers colonized the woody detritus, a second period of rapid exponential mass loss, and a third period of slow decomposition. The consequences for this complex pattern of decomposition were explored at the ecosystem level using a simple model. We found that a single rate constant can be used if inputs vary within a factor of 10, but that this approach is problematical if inputs are more variable.
Modellering av naturlig avgång i Heureka. SLU, inst. f€ or skogens ekologi och sk€ otsel
  • B Elfving
Elfving, B., 2014. Modellering av naturlig avgång i Heureka. SLU, inst. f€ or skogens ekologi och sk€ otsel. http://heurekaslu.org/mw/images/f/f4/HeurekaMortality-PM140317.pdf.
Site Index Estimation by Means of Site Properties. Scots Pine and Norway Spruce in Sweden
  • L Gustafsson
  • S C Baker
  • J Bauhus
  • W J Beese
  • A Brodie
  • J Kouki
  • D B Lindenmayer
  • A Lõhmus
  • G Martinez Pastur
  • C Messier
  • M Neyland
  • B Palik
  • A Sverdrup-Thygeson
  • W J A Volney
  • A Wayne
  • J F Franklin
Gustafsson, L., Baker, S.C., Bauhus, J., Beese, W.J., Brodie, A., Kouki, J., Lindenmayer, D.B., Lõhmus, A., Martinez Pastur, G., Messier, C., Neyland, M., Palik, B., Sverdrup-Thygeson, A., Volney, W.J.A., Wayne, A., Franklin, J.F., 2012. Retention forestry to maintain multifunctional forests: a world perspective. BioScience 62, 633e645. H€ agglund, B., Lundmark, J.E., 1977. Site Index Estimation by Means of Site Properties. Scots Pine and Norway Spruce in Sweden. Studia Forestalia Suecica 138. Swedish College of Forestry, Stockholm.
Structural changes in protected forests in Sweden: implications for conservation functionality
  • P.-O Hedvall
  • G Mikusi Nski
Hedvall, P.-O., Mikusi nski, G., 2015. Structural changes in protected forests in Sweden: implications for conservation functionality. Can. J. For. Res. 45, 1215e1224.