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New methods of oak planting require modification of tending prescriptions under high browsing pressure – A case study from north-eastern Poland
Abstract
Interest in oak species in European forestry has been increasing as they are regarded as having high ability to cope with accelerating anticipated climate changes during the next 50 years. However, improvements in regeneration and silvicultural methods are needed due to oak stands’ high management costs and vulnerability to browsing. Thus, three methods of establishing oak stands were compared in terms of effects on growth and browsing damage in an area of north-eastern Poland with high browsing pressure of roe and red deer. The treatments were traditional monoculture, double-row planting and group planting, each at initial planting densities of 6600, 3300 and 2400 seedling per hectare. Three precommercial thinnings (PCTs) were applied in each planting treatment to reduce competition from early successional species: traditional removal close to the ground in spring, topping in spring and topping in summer. Observed frequencies of oak saplings damaged by browsing depended on both the planting method and PCT treatment. The frequencies were lower under group planting than under the traditional and double-row planting treatments. The frequencies also decreased with increases in the oaks’ height. The results indicate that the optimal PCT treatment to minimise browsing damage depends on the planting pattern. The lowest frequency of damage was in plots where group or double-row planting was combined with spring topping and traditional planting was combined with summer topping. Under heavy herbivory pressure, group planting might be optimal due to its potential to both reduce browsing damage and improve profitability by eliminating fencing costs.
... However, there are substantial obstacles to increasing the abundance of oak in European landscapes, including high costs of planting, protection from browsing and other tending measures in early stages (Annighöfer et al. 2015;Mölder et al. 2019;Löf et al. 2021;Bolibok et al. 2021;Dobrowolska et al. 2020). Increasing salaries and limited numbers of employees interested to work in the silvicultural sector might also exacerbate the problem. ...
... The density of planted seedlings is 2000 to 4000 seedlings ha −1 : 50 to 70 per cent lower than in the conventional method (Joyce et al. 1998;Burschel and Huss 2003). The areas between groups or rows are left for natural regeneration, which is expected to provide overall stand densities and associated conditions that promote the oak trees' growth and quality development (Gockel et al. 2001;Guericke et al. 2008;Saha et al. , 2014Andrzejczyk et al. 2015;Bolibok et al. 2021). Naturally regenerated species enable the formation of mixed stands and support the development of many economic and ecosystem services. ...
... These studies have showed that oak trees planted in groups have comparable quality and growth to those planted traditionally in rows (Skiadaresis et al. 2016;Saha et al. 2017). However, results concerning the growth and quality of oaks planted with wide initial spacing between rows are limited to a few growing seasons after planting, when competition between stems has not yet started (Andrzejczyk et al. 2015;Bolibok et al. 2021). This is an important caveat as the onset of competition is an important factor in the process of natural pruning of the main oak stems, which inf luences the quality of individual stems and improves stands' total value (Spiecker 1991;Attocchi 2015). ...
Traditional oak silviculture is costly due to high initial planting density required to obtain management goals of producing high quality timber. New methods therefore reduce the initial planting density and use a planting pattern that allows the inclusion of naturally regenerated trees of other species. The study presents the results of a 13-year experiment on the growth and quality of sessile oak planted in traditional and three alternative planting patterns. We hypothesized that increasing of initial spacing and use of natural regeneration to compensate for lower intra-specific competition does not deteriorate growth and quality parameters of oak. Breast height diameter, height, slenderness, height of the first live branch, diameter of the thickest branch, stem shape and potential future crop oak trees (PFCT) were measured and analysed. The local competition of admixture species was estimated on the basis of the relationship between the height of the oak and the height of admixture trees in its close proximity. The type of planting pattern had no significant effect on oak diameter, but oak height was greater in the traditional pattern than in alternative patterns. Height of the first live branch was the only qualitative trait that differed significantly between the compared planting patterns. The probability of an oak being selected as a PFCT was similar in traditional and alternative patterns, but PFCT absolute number was increasing with an increase of oak planting density. Analysis of competition of admixture species in alternative methods shows that it can reduce height, diameter and stability of oaks. On the other hand, the probability of trees being selected as a PFCT increases significantly with increasing interspecific competition. We conclude that, with controlled competition and at least moderate natural regeneration, the alternative planting patterns can produce oaks with similar growth and quality to those in the traditional pattern.
... smaller percentage of the seed yield (Löf et al., 2019). Animal population density control and/or protection of regeneration may potentially increase the success of regeneration (Dey et al., 2019;Oliet et al., 2019;Vaz et al., 2019;Muñoz-Rengifo et al., 2020;Bolibok et al., 2021;Borderieux et al., 2021). For some species (e.g., for most Pinus spp.) seed availability can be affected by serotinity (Fernandes and Rigolot, 2007). ...
... Browsing in Quercus robur plantations in Poland was evaluated for three planting designs (single row, double row, and group planting) with three pre-commercial thinnings (Bolibok et al., 2021). The browsing damages on saplings were the lowest in group planting when compared with single or double-row planting, and diminished with the increase of the oaks' height. ...
... The browsing damages were the lowest when pre-commercial thinning was carried out in summer for single row and in spring for double row and group planting. The methods developed promoted regeneration, saving the costs of fencing in areas under high browsing pressure (Bolibok et al., 2021). ...
The renewal and sustainability of the forest stands are attained through regeneration. There are three basic methods to regenerate high forest stands: natural regeneration, direct seeding, and planting. This study reviews the factors affecting regeneration, the three methods of regeneration and the effect of stand structure on regeneration. Overall, regeneration success can be quite variable due to edaphic and climatic conditions, seed losses and/or seedling mortality. The silvicultural system is relevant to the choice of the regeneration method. Natural regeneration is used in selection and irregular shelterwood systems whereas direct seeding and planting are used in uniform shelterwood and clear-cut systems. In the former, stand stocking management is primordial to regeneration success while for the latter are species selection, seed predators and spontaneous vegetation control.
... characteristics. Most regeneration studies evaluate regeneration by quantifying its density and height (Harmer, 2005;Acácio et al., 2007;Barrere et al., 2021;Bolibok et al., 2021;Löf et al., 2021). The traits of the individuals are not evaluated. ...
... For example, the amount of browsing the oaks suffer in the first stages of development can condition oak growth. Browsing tends to be higher for saplings with a height lower than or equal to 100 cm (Borkowski et al., 2017;Bolibok et al., 2021). Detecting this event early can be particularly important in the case of agroforestry systems where grazing occurs and the stands have low-density, slow-growing species such as oaks in a heterogeneous spatial distribution. ...
Regeneration and recruitment are primordial for stand sustainability. However, natural regeneration is usually only evaluated by density and height, so no details are provided regarding the individual traits of the saplings/seedlings. Hence, the findings of these regeneration studies are of limited selection power in future management. The main goal of this study was to develop a new methodology that enables the evaluation of individual quality traits of regeneration in the early stages of stand development so that their future potential development can be assessed. Natural regeneration (NR) was evaluated in each field plot using the conjugation of two new methods: first using the natural regeneration density (NRD) method and second using the new natural regeneration tree classification (NRTC). NRTC is composed of a set of criteria with categorical variables that allow the evaluation of traits of individuals and their potential for future recruitment. In this classification system, five criteria were used, namely, upper story influence to evaluate the competition of the trees of the upper story cast on the regeneration individuals, crown isolation to characterize the competition between saplings, height as a surrogate of sapling development, diameter as a proxy of growth, and tree habit as a proxy of the habit of saplings. To test both methods, we applied them in a case study of Quercus ilex in the montado agroforestry system in Portugal, where different degrees of crown cover coexist. Our results indicated that in 85% of the plots with a crown cover higher than 30%, we could find good-quality natural regeneration oak saplings suited to be recruited and located outside of the upper story crown projection. Only 15% of the plots with a crown cover higher than 30% were dominated by Cistus ladanifer and had almost no oak saplings. In future, we suggest that the NRTC be used in all NR individuals in the forest inventory when the NR density is less than 200 NR individuals ha−1.
... To mitigate damage caused by ungulate browsing in the long term, forest managers should adapt their management process to adapt to the situations caused by the climate change and the impressive growth of ungulate number [59], adopting a silvicultural system with higher regeneration density and with mixed composition [60]. Measures such as fencing [61][62][63], tree guards [64], repellents [65], and natural obstacles [66,67] are solutions to prevent damage from browsing, fraying, and trampling; however, they are costly and require continuous maintenance, which can place a burden on forest managers [68]. ...
Improved forage and living conditions in certain parts of Europe over the past few decades have led to alarming levels of ungulate densities. Consequently, the overabundance of red deer, roe deer, and fallow deer in the Western Plains of Romania has begun to generate issues in the development of young oak stands. In addition to causing damage to the agricultural sector and increasing the risk of vehicle collisions, ungulates are increasing pressure on the forestry sector, mainly through the browsing of young saplings. This study quantifies the levels of ungulate browsing in oak stands using a permanent sample grid of 42 plots in both natural and artificial regeneration areas. A total of 3223 individual saplings were measured, revealing browsing intensities of 49.65% in clearcut systems and 12.8% in continuous forest cover systems. With high ungulate densities identified as the main cause, the Sustainable Population Threshold was calculated using a complex set of indices and compared to the actual numbers of ungulates, both of which were translated into stock unit equivalents. A logistic regression model was developed based on silvicultural and wildlife indices to identify other factors influencing browsing occurrence. The findings indicate that the proportion of forested areas in the hunting ground and the type of silvicultural system are significant factors in the occurrence of browsing. The problem of ungulate overabundance clearly influences forest development, and new solutions should be identified in terms of both forestry and wildlife management.
... A study by Bolibok et al. (2021) into planting pattern and vegetation management of oak plantations in Poland found that the choice of planting and management could reduce browsing pressure by deer in the absence of fences. Browsing damage was lowest where group planting was used (oaks are planted in groups of 24 with approximately 5 m gaps between groups) and competing naturally regenerating species that grew within the gaps were topped (i.e. ...
We conducted a systematic literature review as part of a Forestry Commission (FC) contract to provide good practice technical guidance to manage impacts of mammals on trees, woods, establishing woodlands and treescapes. The review examined both the positive and negative impacts of mammals and existing tree protection options and best practice. Using the PRISMA (‘Preferred Reporting Items for Systematic reviews and Meta-Analyses’) framework (Page et al., 2021), we systematically searched for relevant scientific, peer-reviewed literature. We also conducted targeted organisational searches for grey literature relevant to the objectives within an English context. We then implemented a thematic tagging process to facilitate the synthesis of findings across both types of literature, whilst building a categorised resource bank. Following exclusions, we identified and tagged 281 scientific literature sources and 218 grey literature sources. We identified eight key species or functional groups of mammals (beavers; small mammals; grey squirrels; lagomorphs; pigs and wild boar; deer; livestock including feral sheep and goats and bison; and horses and ponies) that have distinct tree protection approaches available, relating to their ecology, behaviour, type of damage caused and legal restrictions. We also developed a novel ecological framework to categorise tree protection methods according to their strategy of intervention within mammal-tree interactions and applied it to each species/functional group. Finally, we provide an extensive synthesis of the literature for each species or group, detailing literature relating to ecosystem services, damage to trees, identification of that damage, and resultant protection methods identified. This document thus provides a foundation for developing the practitioner-focussed technical guidance.
... At sites with a high number of ungulates, their overall impact may fundamentally limit landscape management [20,21]. Therefore, there is a real need for the development of tools that will reduce the damage to tolerable levels, such as an increased regulation of Agriculture 2023, 13, 1184 2 of 11 herbivore populations, improving local environmental conditions and/or increasing the supply of alternative natural food and preventative measures to reduce the risk of damage, alongside the use of reliable and practicable damage estimation methods [22,23]. Damage estimation methods are particularly important for farmers as they provide direct evidence of the scale of damage and can provide indisputable data on the amount of damage when negotiating for compensation. ...
High numbers of large ungulates are locally accompanied by high levels of damage to field crops, causing economic losses and increased costs for the protection of agricultural fields. Quantifying the levels of damage can be problematic, with the degree of accuracy depending on the method used. The aim of this study was to compare the accuracy, workload and cost of four methods commonly used for estimating damage to wheat fields caused by large ungulates (esp. wild boar) in the Czech Republic. The results suggest that the manual processing of aerial photographs (“Uncrewed Aerial Systems [UAS] with Operator Delineation Method”) was very laborious and the least accurate method, with a high risk of error. In comparison, the automatic evaluation of aerial images (“UAS Crop Height Method”) and the “Ground-Based Assessment” both provided similar results when carefully analyzed and were equally demanding. The “Yield Method”, comparing the net yield from damaged and undamaged areas, provided the same result of assessment and was the least laborious, although it does require the existence of comparable areas and for the conditions to be created in advance before the method is used. Equivalent results were achieved by the UAS Crop Height Method, which we recommend using in cases where the Yield Method cannot be applied.
Competition from neighboring vegetation and browsing by large herbivores are two of the most important factors affecting the structure and dynamics of temperate forests. While the previous literature has been able to identify individual negative effects from competition or browsing, no one has yet identified and quantified both the individual and the joint effects. Still, when plants face both competition and browsing, it is possible that the combined effect is not simply a sum of the individual negative effects, but perhaps a more complicated situation, where plants perform either better (in case there is also a facilitative effect from the neighboring vegetation) or worse (if the effects amplify each other) than they would if experiencing only one of the two factors. In this paper, we focus on regeneration of oak (Quercus robur L) to study these questions. We analyze a rich data set from a large long-term field experiment conducted at multiple sites in mixed temperate forests in southern Sweden over almost a decade. By the use of four separate treatments on each site – (i) neither competition, nor browsing, (ii) only competition, (iii) only browsing, and (iv) both competition and browsing – we can identify and quantify both the individual and combined effects of competition and browsing on oak growth and survival. We find that both competition and browsing individually affect growth and survival negatively. For growth, browsing has the largest effect, while competition is the larger problem from a survival point of view. When the plant experiences both competition and browsing, the combined, negative, effect is larger than either individual effect for survival, but for growth, the relationship is more complicated, and the surrounding woody vegetation offers at least some protection for the oak, reducing the negative effects from browsing.
One of the most important ecosystem processes, especially in temperate and boreal forests, is herbivore browsing. In this study, we tested five hypotheses: (H1) oak tree density would positively affect their height; (H2) despite severe browsing pressure, the height of oaks would increase with the age after planting; (H3) oaks growing among the planted pines would be taller than those among the sown ones; (H4) the growth of single oak saplings or of oak nests would be positively affected by the height of the pines growing in the immediate neighbourhood of the oaks; and (H5) the oak height would be affected by the location within a nest and oaks growing in the central zone would be taller than the others. The study was conducted in the Piska Forest in the north-eastern part of Poland. We established three variants of experiment. In the first variant, oaks were planted individually. In the second and third variants, oaks were planted in small nests. The second and third variants differed in the spacing of the nests: 8 × 8 m and 6 × 6 m, respectively. The division into the sub-variants referred to type of pine regeneration. In the first sub-variant, Scots pine was planted. In the second, pine was sown. In general, oaks growing within nests were significantly taller than those planted individually in the Scots pine rows. Despite heavy browsing, oak height consistently increased during the course of the study. Oak height also depended on the type of pine regeneration, and the mean height of oaks surrounded by planted pines was significantly higher than that of oaks surrounded by sown pines (which, in average, was shorter). That was because the planted pines were taller than the sown ones. We found that Spearman’s correlation coefficients were positive and significant between pine and oak heights in variants 2 and 3. Growth of oaks did not depend on their location within a nest. The results of the regeneration method of oak (single vs nest and few vs many nests) are modified by browsing. The best method found in the heavy browsing circumstances was planting oaks in many nests within successful pine regeneration (providing the oaks with protection against the browsing). The pine will provide the most efficient protection if regenerated a few years before the oaks.
Count data can be analyzed using generalized linear mixed models when observations are correlated in ways that require random effects. However, count data are often zero-inflated, containing more zeros than would be expected from the typical error distributions. We present a new package, glmmTMB, and compare it to other R packages that fit zero-inflated mixed models. The glmmTMB package fits many types of GLMMs and extensions, including models with continuously distributed responses, but here we focus on count responses. glmmTMB is faster than glmmADMB, MCMCglmm, and brms, and more flexible than INLA and mgcv for zero-inflated modeling. One unique feature of glmmTMB (among packages that fit zero-inflated mixed models) is its ability to estimate the Conway-Maxwell-Poisson distribution parameterized by the mean. Overall, its most appealing features for new users may be the combination of speed, flexibility, and its interface's similarity to lme4.
There is little knowledge how ungulate pressure on forest regeneration may be mitigated by silvicultural methods. The knowledge is especially needed for artificially regenerated, deciduous tree species. We studied factors affecting browsing incidence by deer in the Pisz Forest District in Poland, an area where 10,000 ha of forest was damaged by a 2002 hurricane. In 2006, we established three experimental plots (in total, 22.6 ha), in which the main species was Scots pine (Pinus sylvestris) admixed with pedunculate oak (Quercus robur). The data on browsing were collected in 2008–2015. In general, oak browsing incidence was unrelated to oak planting density. On a plantation scale, it was significantly affected by the pine age. Although in each variant all the oaks were browsed for four consecutive years (2009–2012), in 2013 browsing incidence began to decrease. When the pines grew higher and formed a physical barrier, it was harder for deer—roe deer (Capreolus capreolus), red deer (Cervus elaphus) and moose (Alces alces)—to move through and locate the oaks. Moreover, within plantations, oak browsing incidence was higher in the patches with shorter pines. Browsing of individual saplings or small groups of saplings was also negatively affected by the height of neighbouring pine saplings. Oak density influenced deer selectivity depending on the tree height. In a low oak tree density, browsing incidence was unrelated to oak height, while in higher tree density, deer selected oaks of the height between 40 and 100 cm. We postulate that deciduous admixture in a coniferous (unattractive) stand can be planted with a few year delay. Older coniferous trees should impede locating of attractive tree species by deer and the browsing incidence.
Recent studies have reported superior tree quality and comparable tree growth of oaks planted in group compared with row planting. However, a comparative assessment of the potential future crop trees (PFCTs) between group and row planting is still lacking. Here, we compared the density and tree quality of planted oaks and other naturally regenerated trees between group and row planting. We assessed whether the distribution of PFCTs fulfills the goal of maintaining a spatially homogenous distribution of such crop trees at the stand level by geospatial analysis. We selected 10 group and row planting stands that were either 14 to 15 or 21 to 22 years old. Tree density in group plantings was significantly higher than in row plantings. Stand basal area was higher in row planting in younger stands but comparable to group planting in older stands. The proportion of trees with straight stems and monopodial crowns was higher in groups than in rows. The density and species’ richness of the PFCTs was significantly higher but the number of oak PFCTs was lower in group than in row plantings. In group plantings, naturally regenerated PFCTs contributed to 43% of total PFCTs, but to only 19% in row plantings. Also, the spatial distribution of PFCTs in group plantings was more uniform than in row plantings. Uniform and homogeneous distribution of the PFCTs in group planting stands can facilitate design and conduct of tending operations. Thus, the group planting technique offers not only cost savings in the establishment phase but also additional benefits, including spreading of risks through increased tree species diversity.
Oaks (Quercus spp.) are becoming increasingly important for future forest management as the climate in central Europe warms. Owing to the high costs of conventional row planting, artificial oak stand establishment in the form of “clusters” became popular in central Europe beginning in the 1970s. In cluster plantings, oaks are planted either in groups of ca. 20–25 at 1 m spacing between trees (i.e., group planting) or in denser groups with 20–30 oaks·m⁻² (i.e., nest planting). In both cases, the clusters are spaced apart at a distance that represents the target density of future crop trees. A comprehensive review of the history, growth, tree quality development, and economic aspects of oak cluster plantings suggests that initial growing space was the most important factor influencing development of oaks in clusters. Consequently, survival, growth, quality, and biomass production were comparable in group and row plantings but lower in nest plantings. In addition, group plantings resulted in greater stand-level tree species diversity than nest or row plantings. We conclude that oak group planting is a comparatively inexpensive option for the artificial regeneration of oak-dominated broadleaved forests for a range of situations such as reforestation of disturbed areas or the afforestation of abandoned agricultural land. Future research needs regarding development and tending of forests established by oak group planting are highlighted.
A conversion of previously even-aged pine-dominated forests to uneven-aged and multi-functional oak-dominated forests has been ongoing since 1993 in the Pyramida experimental forest (95 ha) situated in the buffer zone of Podyjí National Park, Czech Republic. Based on repeated surveys in 1992, 2003 and 2013, the conversion was assessed according to changes in: (i) the proportion of species; (ii) the distribution of DBH; (iii) the distribution of patches; and (iv) the distribution of forest types. The proportion of conifers decreased from 61.0% to 42.0%, and the proportion of broadleaved species increased accordingly. A sharp decline in the number of trees in the DBH class 70-109 mm was caused by the intense release of understorey broadleaved trees in young Scots pine small pole stage stands. The number of large habitat trees steadily increased in the DBH classes 430+ mm. The mean size of one patch decreased from 0.8 ha (1992) to 0.4 ha (2013). The spatial proportion of the target forest type (uneven-aged oak-dominated forest) increased from 8.5% in 1992 to 45.0% in 2013, and 35.1% of the area was fully converted during the 20 years. We expect 69.1% of the area to be converted after 30 years (2023).
Identification of the ecosystem services provided by oak-dominated forests in southern Sweden is a prerequisite for ensuring their conservation and sustainable management. These forests seem well-suited for multiple-use forestry, but knowledge is limited regarding how to manage them for multiple uses. Management for the production of high-value timber species like oaks and management to conserve biodiversity, or for cultural services can be in conflict with each other. This study evaluates the capacity of three contrasting management regimes to provide societies with economic revenue from timber production, habitats for biodiversity and cultural services, and the study analyses associated trade-offs and synergies. The three regimes were: intensive oak timber production (A), combined management for both timber production and biodiversity (B) and biodiversity conservation without management intervention (C). We synthesized relevant scientific literature, governmental statistics and grey literature. Our assessments identified that Regime A provided the highest levels of economic returns and the lowest level of biodiversity. Regime C provided higher levels of habitat provision but at expense of wood production and cultural services. In contrast, Regime B provided a balanced delivery of timber production, biodiversity conservation and cultural services. We identified several stand-management options which provide comparatively synergistic outcomes in ecosystem services delivery. The use of these management options in combination with more traditional stand-management approaches may be a more effective means of achieving sustainable forest goods and services.
EDITED BY Nicholas Brokaw
Quercus robur L. (pedunculate oak) and Quercus petraea (Matt.) Liebl. (sessile oak) are two European oak species of great economic and ecological importance. Even though both oaks have wide ecological amplitudes of suitable growing conditions, forests dominated by oaks often fail to regenerate naturally. The regeneration performance of both oak species is assumed to be subject to a variety of variables that interact with one another in complex ways. The novel approach of this research was to study the effect of many ecological variables on the regeneration performance of both oak species together and identify key variables and interactions for different development stages of the oak regeneration on a large scale in the field. For this purpose, overstory and regeneration inventories were conducted in oak dominated forests throughout southern Germany and paired with data on browsing, soil, and light availability. The study was able to verify the assumption that the occurrence of oak regeneration depends on a set of variables and their interactions. Specifically, combinations of site and stand specific variables such as light availability, soil pH and iron content on the one hand, and basal area and species composition of the overstory on the other hand. Also browsing pressure was related to oak abundance. The results also show that the importance of variables and their combinations differs among the development stages of the regeneration. Light availability becomes more important during later development stages, whereas the number of oaks in the overstory is important during early development stages. We conclude that successful natural oak regeneration is more likely to be achieved on sites with lower fertility and requires constantly controlling overstory density. Initially sufficient mature oaks in the overstory should be ensured. In later stages, overstory density should be reduced continuously to meet the increasing light demand of oak seedlings and saplings.
Publication details, including instructions for authors and subscription information: http://www.informaworld.com/smpp/title~content=t713711862 Effects of roe deer browsing and site preparation on performance of planted broadleaved and conifer seedlings when using temporary fences Full terms and conditions of use: http://www.informaworld.com/terms-and-conditions-of-access.pdf This article may be used for research, teaching and private study purposes. Any substantial or systematic reproduction, redistribution , reselling , loan or sub-licensing, systematic supply or distribution in any form to anyone is expressly forbidden. The publisher does not give any warranty express or implied or make any representation that the contents will be complete or accurate or up to date. The accuracy of any instructions, formulae and drug doses should be independently verified with primary sources. The publisher shall not be liable for any loss, actions, claims, proceedings, demand or costs or damages whatsoever or howsoever caused arising directly or indirectly in connection with or arising out of the use of this material.
We studied the effect of roe deer (Capreolus capreolus) browsing on the growth and mortality of sessile oak (Quercus petraea) seedlings. First, we measured the height and basal diameter, and counted the number of shoots of the 849 seedlings of an experimental plantation, 60 of which were individually protected by fencing. We then introduced two tame roe deer females every day for three weeks from late May to mid June. Measurements and counts were repeated after roe deer removal, then once again the following winter. We found no significant effect of browsing on either mortality, total height, or basal diameter of the seedlings. However, the browsed seedlings exhibited a lower number of shoots despite regrowth observed after roe deer removal. We propose to use the tolerance of oak to deer browsing to promote natural and inexpensive methods, to protect oak during regeneration, such as the spatial arrangement of plants or the use of slash or surrounding vegetation in favourable environments.
In many parts of Europe, close-to-nature silviculture (CNS) has been widely advocated as being the best approach for managing
forests to cope with future climate change. In this review, we identify and evaluate six principles for enhancing the adaptive
capacity of European temperate forests in a changing climate: (1) increase tree species richness, (2) increase structural
diversity, (3) maintain and increase genetic variation within tree species, (4) increase resistance of individual trees to
biotic and abiotic stress, (5) replace high-risk stands and (6) keep average growing stocks low. We use these principles to
examine how three CNS systems (single-tree selection, group selection and shelterwood) serve adaptation strategies. Many attributes
of CNS can increase the adaptive capacity of European temperate forests to a changing climate. CNS promotes structural diversity
and tree resistance to stressors, and growing stocks can be kept at low levels. However, some deficiencies exist in relation
to the adaptation principles of increasing tree species richness, maintaining and increasing genetic variation, and replacing
high-risk stands. To address these shortcomings, CNS should make increased use of a range of regeneration methods, in order
to promote light-demanding tree species, non-native species and non-local provenances.
Anti-predator responses by ungulates can be based on habitat features or on the near-imminent threat of predators. In dense forest, cues that ungulates use to assess predation risk likely differ from half-open landscapes, as scent relative to sight is predicted to be more important. We studied, in the Białowieża Primeval Forest (Poland), whether perceived predation risk in red deer (Cervus elaphus) and wild boar (Sus scrofa) is related to habitat visibility or olfactory cues of a predator. We used camera traps in two different set-ups to record undisturbed ungulate behavior and fresh wolf (Canis lupus) scats as olfactory cue. Habitat visibility at fixed locations in deciduous old growth forest affected neither vigilance levels nor visitation rate and cumulative visitation time of both ungulate species. However, red deer showed a more than two-fold increase of vigilance level from 22% of the time present on control plots to 46% on experimental plots containing one wolf scat. Higher vigilance came at the expense of time spent foraging, which decreased from 32% to 12% while exposed to the wolf scat. These behavioral changes were most pronounced during the first week of the experiment but continuous monitoring of the plots suggested that they might last for several weeks. Wild boar did not show behavioral responses indicating higher perceived predation risk. Visitation rate and cumulative visitation time were not affected by the presence of a wolf scat in both ungulate species. The current study showed that perceived predation risk in red deer and wild boar is not related to habitat visibility in a dense forest ecosystem. However, olfactory cues of wolves affected foraging behavior of their preferred prey species red deer. We showed that odor of wolves in an ecologically equivalent dose is sufficient to create fine-scale risk factors for red deer.
The growth behavior of coexisting tree species under climate change is important from an ecological, silvicultural and economic perspective. While many previous studies are concerned with climatic limits for species occurrence, we focus on climate related shifts in interspecific competition. A landmark for these changes in competition is the 'climatic turning point' (CTP): those climate conditions under which a rank reversal between key tree species occurs. Here, we used a common type of temperate mixed forest in Central Europe with European beech (Fagus sylvatica L.) and sessile oak (Quercus petraea (Matt.) Liebl.) to explore the CTP under a future climate projection of increasing temperature and aridity. We selected a dry region where the prerequisite of differential climate sensitivity in mixed beech-oak forests was fulfilled: In-situ dendrochronological analyses demonstrated that the currently more competitive beech was more drought sensitive than sessile oak. We then used two complementary forest growth models, namely SILVA and LandClim, to investigate the climate induced rank-reversal in species dominance and to quantify it as the CTP from beech to oak by simulating future forest development from the WETTREG 2010 A1B climate projection. Utilizing two models allowed us to draw conclusions robust against the assumptions of a particular model. Both models projected a CTP at a mean annual temperature of 11–128C (July temperature .188C) and a precipitation sum of 500–530 mm. However, the change in tree species composition can exhibit a time-lag of several decades depending on past stand development and current stand structure. We conclude that the climatic turning point is a simple yet effective reference measure to study climate related changes in interspecific competition, and confirm the importance of competition sensitivity in climate change modeling.
Low density plantings complemented by natural regeneration is an increasingly common reforestation technique to ensure growth of a sufficient number of trees from desired species while maintaining natural processes such as succession. One such form of low density planting that aims at lowering establishment costs—oak clusters—has been developed as an alternative to row planting since the 1980s in central Europe. However, whether cluster planting provides higher species richness and productivity than high density row planting has not previously been analyzed. Here, we compare tree species richness and productivity (measured as stand basal area) between oak cluster plantings and conventional row planting in young (10–26 years old) forest stands at seven study sites in Germany. Tree species richness was significantly higher in cluster plantings than in row plantings, whereas total basal areas were comparable. Naturally regenerated trees contributed on average to 43% of total stand basal area in cluster plantings, which was significantly higher than in row plantings. Total stand basal area in cluster planting was significantly related to the density of naturally regenerated trees. In turn, tree species diversity, density and basal area of naturally regenerated trees were increased with the size of unplanted area between clusters. Our results demonstrate that the admixture of naturally regenerated, early and mid-successional tree species compensates for a possible loss in productivity from planting fewer oaks. Low density cluster plantings can offer significant environmental benefits, at least for the first few decades of stand development, without compromising productivity.
Absence of, or poor, oak ( Quercus spp.) regeneration is a problem in uneven-aged, mixed closed-canopy broadleaved forests. Browsing by ungulates on small trees may contribute to poor oak regeneration in such forests. This possibility was investigated in 25 Swedish stands, and browsing damage was analysed in relation to landscape and stand factors. The proportion of browsed small ( Keywords: Mixed closed-canopy forest; Quercus; oak and broadleaved trees; oak regeneration; ungulate browsing Document Type: Research Article DOI: http://dx.doi.org/10.1080/02827580510008383 Affiliations: 1: Department of Zoology, Göteborg University, Göteborg, Sweden 2: Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden 3: Mathematical Statistics, Department of Mathematics, Göteborg University and Chalmers University of Technology, Göteborg, Sweden Publication date: May 1, 2005 More about this publication? Editorial Board Information for Authors Subscribe to this Title ingentaconnect is not responsible for the content or availability of external websites (document).ready(function() { var shortdescription = (".originaldescription").text().replace(/\\&/g, '&').replace(/\\, '<').replace(/\\>/g, '>').replace(/\\t/g, ' ').replace(/\\n/g, ''); if (shortdescription.length > 350){ shortdescription = "" + shortdescription.substring(0,250) + "... more"; } (".shortdescription a").click(function() { (".originaldescription").slideDown(); return false; }); }); Related content In this: publication By this: publisher In this Subject: Forestry By this author: Götmark, Frank ; Berglund, Åsa ; Wiklander, Kerstin GA_googleFillSlot("Horizontal_banner_bottom");
A habitat suitability model for roe deer (Capreolus capreolus) including indices of forest predisposition to browsing damage was tested in an alpine forest region dominated by spruce (Picea abies). A description of the habitat model is presented. Eleven input parameters were weighted and aggregated to the habitat indices hiding cover, thermal cover, lounge index and food supply. These indices are basis for the overall habitat quality and predisposition to browsing damage scores. The sensitivity of the model to the input parameters total ground vegetation, ground vegetation without grass, woody ground vegetation, share of forest regeneration, total crown projection, crown projection of deciduous trees, wildlife ecological stand type, edge density, mesorelief, altitude, and aspect was tested. The model was most sensitive to the parameters (i) abundance of total ground vegetation without grass, (ii) abundance of woody ground vegetation, (iii) wildlife ecological stand type, and (iv) mesorelief. Total abundance of ground vegetation and aspect affected sensitivity least. A trade-off index for habitat quality versus predisposition to browsing damage showed most sensitivity to food supply and least to edge effect. The habitat model is linked with a forest growth model and therefore allows long-term predictions of habitat and browsing predisposition changes in dependence on different silvicultural treatments. Consequences in terms of wildlife and forest management are discussed.
Plant responses to mammalian herbivores can be manifold. Browsing by large mammals such as moose may change plant growth and morphology, which, in turn, will change the food quality and availability for e.g. invertebrate herbivores sharing the same forage plant. Furthermore, the intensity and timing of herbivory may affect plant responses and future herbivore attack. In a field experiment, we tested whether simulated summer browsing and natural winter browsing by moose affects growth and morphology of birch Betula pendula, and whether possible changes had effects on abundance and defoliation by herbivorous invertebrates. The simulated summer browsing treatment was applied in two intensities (50% and 100% defoliation of long shoots) during two different periods of the growth season (mid-June and mid-July). Simulated summer browsing delayed the timing of budburst, reduced height and diameter growth and resulted in reduced defoliation by invertebrate herbivores indicating an induced defence. Winter browsing by moose reduced diameter growth, leaf biomass of short shoots but increased height growth, the abundance of aphids and defoliation by insect herbivores. The effects of herbivory on the timing of budburst, leaf biomass of long and short shoots and the abundance of aphids were more pronounced when the birches were both browsed in winter and artificially stripped. The timing of the artificial leaf stripping treatment was important for nearly all tested variables. Concluding, summer and winter browsing by moose can have opposing or additive effects on plant morphology and growth. Therefore, also indirect effects of mammalian herbivory on invertebrate communities feeding on the same plant may differ, depending on the browsing intensity, the season of browsing and even the timing of browsing within the same season.
Climatic warming may lead to increased or decreased future forest productivity. However, more frequent heat waves, droughts and storms and accompanying pathogen attacks are also expected for Europe and are considered to be increasingly important abiotic and biotic stress factors for forests. Adaptive forestry can help forest ecosystems to adapt to these new conditions in order to achieve management goals, maintain desired forest ecosystem services and reduce the risks of forest degradation. With a focus on central Europe, this paper presents the following management strategies: (1) conservation of
forest structures, (2) active adaptation, and (3) passive adaptation. The feasibility and criteria for application of the different strategies are discussed. Forest adaptation may entail the establishment of ‘‘neonative’’ forests, including the use and intermixing of native and non-native tree species as well as non-local tree provenances that may adapt better to future climate conditions. An integrative adaptive management concept is proposed that combines (1) species suitability tests and modelling activities at the international scale, (2) priority mapping of adaptation strategies at the national to regional scale, and (3) implementation at the local scale. To achieve this, an international experimental trial system is required to test suitable adaptive measures throughout Europe and worldwide.
Broadleaved trees represent 37 % of the forest resource of Europe; equating to 9 % of the world's forest resource. The high number of broadleaved species (c. 80), many of which are 'minor', is reflected in a lack of adequate information on their distribution and state of health. Existing and projected impacts of climate change on the broadleaved resource are reviewed, as are future possible socio-economic drivers for forest management. Assisting the European forest resource and the sector to adapt to change, and to exploit opportunities, may take the form of broader species and provenance choice, new approaches to forest design, and more support for research, particularly tree breeding. Production forestry may benefit in some regions with changes in yield and the development of stronger markets for hardwoods as a substitute for tropical hardwoods or fossil fuel-derived materials in construction, and for bio-energy markets.
Deer have expanded their range and increased dramatically in abundance worldwide in recent decades. They inflict major economic losses in forestry, agriculture, and transportation and contribute to the transmission of several animal and human diseases. Their impact on natural ecosystems is also dramatic but less quantified. By foraging selectively, deer affect the growth and survival of many herb, shrub, and tree species, modifying patterns of relative abundance and vegetation dynamics. Cascading effects on other species extend to insects, birds, and other mammals. In forests, sustained overbrowsing reduces plant cover and diversity, alters nutrient and carbon cycling, and redirects succession to shift future overstory composition. Many of these simplified alternative states appear to be stable and difficult to reverse. Given the influence of deer on other organisms and natural processes, ecologists should actively participate in efforts to understand, monitor, and reduce the impact of deer on ecosystems.
Purpose:
Droughts are expected to become more intense and frequent. Mixed forests can be more resilient to extreme events, but are the individual trees in mixed forests also more resilient to drought?
Methods:
We sampled 275 trees in 53 temperate forest stands in northern Belgium: monocultures, two-species mixtures, and the three-species mixture of Fagus sylvatica, Quercus robur, and Q. rubra. We related the annual basal area increment of individual trees to drought severity from 1955 to 2015 and calculated growth resistance, recovery, and resilience for six contrasting drought episodes (spring, summer, or full-year drought).
Results:
Tree growth of the diffuse-porous F. sylvatica was more sensitive to drought, summer drought in particular. The ring-porous Q. robur and Q. rubra were mainly affected by spring drought. In general, a tree's growth response to drought was not affected by tree species diversity, but some identity effects emerged.
Conclusion:
The asynchrony in drought responses among the tree species (a large and immediate decrease in growth followed by swift recovery in F. sylvatica vs a smaller delayed response in Quercus) might stabilize productivity in forests in which both are present. The impact of the predicted increasing drought frequency will depend on the timing of the droughts (spring vs summer).
Although numerous species distribution models have been developed, most were based on insufficient distribution data or used older climate change scenarios. We aimed to quantify changes in projected ranges and threat level by the years 2061-2080, for 12 European forest tree species under three climate change scenarios. We combined tree distribution data from the Global Biodiversity Information Facility, EUFORGEN and forest inventories, and we developed species distribution models using MaxEnt and 19 bioclimatic variables. Models were developed for three climate change scenarios – optimistic (RCP2.6), moderate (RCP4.5) and pessimistic (RPC8.5) – using three General Circulation Models, for the period 2061-2080. Our study revealed different responses of tree species to projected climate change. The species may be divided into three groups: “winners” – mostly late-successional species: Abies alba, Fagus sylvatica, Fraxinus excelsior, Quercus robur and Q. petraea; “losers” – mostly pioneer species: Betula pendula, Larix decidua, Picea abies and Pinus sylvestris and alien species – Pseudotsuga menziesii, Q. rubra and Robinia pseudoacacia, which may be also considered as “winners”. Assuming limited migration, most of the species studied would face significant decrease of suitable habitat area. The threat level was highest for species that currently have the northernmost distribution centers. Ecological consequences of the projected range contractions would be serious for both forest management and nature conservation. This article is protected by copyright. All rights reserved.
Facilitation by a neighboring woody understory has been suggested as a cost-effective and sustainable way to regenerate oaks. However, concerns about reduced plant growth and quality due to competing neighboring vegetation have hindered implementation. Here we studied competitive effects from herbaceous and woody vegetation on survival, growth, canopy development and stem quality in pedunculate oak (Quercus robur) in an open-field experiment in southern Sweden. Oaks were grown for eight years in four different competition treatments: no competing vegetation, with herbaceous vegetation (mainly grasses), with woody vegetation, and with both herbaceous and woody vegetation. During the first four years, competition had little effect on oak survival. However, after eight growing seasons, survival rates decreased to about 20% for oaks surrounded by woody vegetation, in contrast to oaks grown with only herbaceous vegetation that had a survival rate of near 100%. Competition from herbaceous and woody vegetation both reduced oak stem diameter and height growth, but they affected height growth differently. During the first growing seasons, oaks in the treatment with woody vegetation were able to keep up with the height growth of the surrounding vegetation. Thereafter, height growth stagnated, and after eight growing seasons heights of oaks in the treatment with woody competitors were only 30–39% that of oaks in the treatment without competing vegetation. In contrast, competition from herbaceous vegetation only restricted oak height development marginally. Interspecific competition not only restricted growth and survival but also shifted shoot architecture, resulting in a greater frequency of oaks with straight monopodial stems. Although competition from both herbaceous- and woody vegetation positively affected stem straightness, plots with woody vegetation had a greater proportion (0.42) of oaks with a single straight monopodial stem. Our results demonstrate that the facilitative competitive effects from herbaceous and woody vegetation could be used to control allocation patterns in young oaks, promoting development of tall straight monopodial stems. Considering the observed trade-off between high stem quality and survival, we recommend long-term assessment of this trade-off prior to application in practical forestry.
We examined growth and quality of young oaks in stands established at three different spacings. The three densities were the traditional level, i.e. 8 000 seedlings ha-1 (1.5 × 0.85 m) plus two where the initial density was decreased by 50 and 70%, achieved by increasing the distance between the rows from 1.5 to 3 or 4.5 m. The experiment was located in central Poland on moderately fertile site. In the two wider spacings the intention was to use natural regeneration occurring between oak rows as a replacement of intraspecific competition for oaks. The mean height was only affected in the third and the fourth year after establishment. Subsequently, the differences between spacings with respect to both growth and quality traits were insignificant and small. At lower densities, natural regeneration of willow and aspen was abundant and inter-species competition replaced intra-species competition, thus explaining the absence of a spacing effect on growth and quality properties. In the study period, the wider spacings were economically beneficial compared to traditional densities. A strong competition affecting height growth caused by natural regeneration necessitated extensive tendings. More tendings are likely to be needed in the future and they might reduce the initial economical superiority of wider spacing. The study indicates that it is possible to decrease the initial spacing in oak plantations and simultaneously support good growing conditions by means of natural process e.g. natural regeneration. However, economic efficiency of the method has to be studied in a longer perspective.
Little comprehensive research on forest-ungulate interactions has been undertaken to gain a holistic and deep understanding of the ecological, social and economic interdependencies regarding this sensitive topic. The understanding is mainly constrained by the complexity of the topic, which is further determined by large temporal and spatial scales. For future research as well as for practical implementation, a set of more than a few factors have to be included in study designs. The aim of this study is to present a comprehensive overview of factors and mechanisms which can be modified to address deer impact in function-oriented silviculture. We used the approach of vote-counting to assess not only numerical data from primary literature, but also descriptive findings from conclusions and discussions in the numerous but heterogenic literature on the topic. To mitigate bias introduced in such literature surveys by individual researchers, we used group discussions to extract commonly agreeable results. We surveyed 38 studies from Europe dealing with red deer (Cervus elaphus), roe deer (Capreolus capreolus) and fallow deer (Dama dama). We found 185 mentions of 80 distinct factors determining browsing, bark stripping and fraying impact of these large ungulates. We provide an overview of the factors, describe the way in which they are correlated with deer impact and suggest ways to incorporate our findings in future research and management practice. Most of the broad variety of factors were related to forest properties and structure, but also disturbance and site features were relevant. We found evidence that most factors are modifiable by silvicultural means but can be overruled where deer density or disturbance of the deer population are locally in excess. Thus, our literature survey highlights the necessity of research and management approaches that integrate forest management, hunting and other stakeholder effects on deer impact.
Pedunculate oak (Quercus robur) and sessile oak (Q. petraea) are likely to become increasingly important in Central Europe owing to their stability, tolerance of relatively warm climates, and their valuable timber. Although natural regeneration is often the preferred option for oak stand establishment in many regions of Central Europe, planting and seeding still play a major role in the reforestation of oak-dominated forests. Artificial regeneration is the only way to establish oak stands in situations where acorn sources are lacking. In particular, this is the case where coniferous stands are to be converted to oak forests, where competition from herbaceous and woody plants hinders the natural regeneration of oak, or where oak stands are to be established in cleared areas following storms or other disturbances. Planting oak seedling in rows with a high initial density (e.g. 5,000 – 7,000 seedlings ha-1) is often used for artificial regeneration of oaks. However, high costs associated with site preparation (particularly in wind-thrown areas), planting, fencing and successive tending measures remain a matter of concern for conventional row planting of oaks. These considerations may apply equally to the artificial regeneration of other hardwood species.
Such factors motivated foresters and researchers to seek alternatives to the establishment of oak stands. Low-density planting, where the artificial regeneration of the desired species is complemented by natural regeneration of additional species is one such approach to reduce costs and to maintain successional processes and increase biodiversity at the same time. For oaks, low density planting in the form of widely spaced clusters with two different designs has been developed in Europe. Clusters comprising 20 to 30 seedlings are either ‘nests’ (nest planting) with very dense spacing of ca. 0.2 m between trees, or ‘groups’ (group planting) with 1 m between trees. In contrast to nests plantings, clusters in group plantations are encircled with a varying number of individuals of a trainer tree species (e.g. Tilia cordata, Carpinus betulus). Commonly, ca. 100 groups or 200 nests ha-1 were planted in uniform distribution. This new oak regeneration technique became popular in the 1980s and 1990s to reforest wind-thrown area created by catastrophic winter hurricanes in the 1990s (“Vivian” and “Wiebke” in 1990 and “Lothar” in 1999). Although many cluster planting trials were established since then, no comprehensive analysis had been carried out to study growth and quality attributes related to timber production in oaks grown in cluster planting. In addition, natural regeneration in the space between the clusters, stand productivity and the influence of naturally regenerated trees on growth and stem quality of oaks grown in clusters had never been studied. Therefore, the objectives for this study were as follows: 1) to compare comprehensively survival, growth (diameter at breast height or DBH, height), stability (height-to-DBH ratio), and quality (stem form, crown shape, branch free bole length, potential future crop tree) of oaks grown in clusters when compared to conventional row planting; 2) to assess and compare tree species diversity and stand productivity in stands established through cluster and row planting; and to test further whether stand productivity in cluster planting stands may be influenced by species richness and density of the naturally regenerated and planted trees; and 3) to quantify influences from intraspecific and interspecific interactions on growth and quality of oaks in mixed stands established through cluster planting.
The first objective was addressed by synthesizing original forest inventory data gathered and collected from 25 trial pairs consisting of cluster and respective neighbouring row planting sites (ca. 5,000 seedlings ha-1) located in Germany, Switzerland and Austria and carrying out a meta-analysis. The second and third objectives were addressed by analysing data from 7 cluster trials located in Baden-Württemberg and Hessen, Germany. Again, row plantings counterparts were used for the comparison of the investigated stand establishment methods.
The comprehensive mixed effect meta-analysis revealed that tree survival, growth and quality were significantly lower in nests than in neighbouring row planting counterparts. Intense intraspecific competition due to very low initial growing space (only 0.04 m2 per seedling) was presumably one of the main reasons for low survival, unfavourable growth and quality development of oaks in nest plantings. However, in group plantings which provided larger initial growing space (1 m2 per seedling), survival, growth and tree quality were similar or superior to row plantings. The meta-analysis also showed that tree quality benefitted from the presence of trainer trees in group plantings.
Species richness and diversity were significantly higher in cluster plantings than in row plantings. Basal area of naturally regenerated trees (e.g. Betula pendula, Populus spp., Salix spp., Acer pseudoplatanus, Sorbus aucuparia) contributed to ca. 43% of total stand basal in cluster plantings and was significantly higher than in row plantings. As a result total stand basal area did not differ significantly between the analysed stand establishment methods. Productivity of stand established through cluster planting was significantly related to density of naturally regenerated species.
Competition from mid- and late successional tree species had a stronger negative impact on growth of target oak trees than competition from oaks and early successional tree species. Intraspecific competition was sufficient to promote self-pruning in oaks grown in clusters. Additional, interspecific competition did not further advance the branch-free bole length of target oaks. Oaks grown in the inner part of groups showed higher probability to develop into potential future crop trees than oaks grown in the periphery of groups. This study also showed that in the majority of groups (80%) in a 20-year old stand at least one potential future crop tree developed.
Based on this study, it can be concluded that owing to high mortality, poor growth and inferior stem quality, oak nest planting should not be pursued further to establish oak stands. In contrast, oak group plantings can be recommended as a suitable alternative to conventional row planting. Significant environmental (high species richness and productivity), silvicultural (quality development in oaks) and economic (e.g. low site preparation and plantings cost) gains can be achieved with low-density planting of oaks in groups.
In Sweden, moose (Alces alces) feed to a large extent on birches (Betula pendula and B. pubescens). This study examined responses of juvenile birches to moose browsing and the responses of moose to browsed trees. Following browsing, the birches produced larger shoots with larger and more chlorophyll-rich leaves than did unbrowsed birches. Shoots on browsed trees had a longer growing season and contained less Ca, Mg, and crude fat than did shoots on unbrowsed trees. After browsing, some resting buds and buds on some of the short shoots developed into long shoots, a response that was more frequent in an open habitat than in a shaded one. The birches thus showed substantial compensatory growth following browsing by moose. Most of the potential buds were not transformed into long shoots, even though more growth was allocated to each individual shoot. For moose this mean that at moderate browsing pressures (1) the production of shoot biomass was maintained, (2) the available forge increased because the shoot growth was kept at lower positions, and (3) browsing was facilitated by the larger shoot size, but (4) the contents of Ca, Mg, and crude fat in the shoots decreased. Of the two similar birch species, moose preferred B. pendula to B. pubescens. This supports the hypothesis that plants with slow growth rates (B. pubescens) are less preferred by browsers than plants with high growth rates (B. pendula). Further, we found no support for the occurrence of induced defense in juvenile trees; those that had been browsed during the previous winter were more palatable than previously unbrowsed trees.
Ambush predators provide more persistent cues of predation risk compared to coursing predators
and are predicted to exert stronger effects on behaviour of their prey. We studied anti-predator
responses of ungulates by means of camera traps to an olfactory cue (fresh scat) of an ambush
predator, the Eurasian lynx (Lynx lynx). Roe deer (Capreolus capreolus) and red deer (Cervus
elaphus) both important prey species for lynx were not more vigilant when exposed to lynx scent,
but reduced their visitation duration. Our results contrast with previously reported responses of red
deer to scent from a coursing predator, the wolf (Canis lupus), where only vigilance and foraging
behaviour but not visitation duration changed in response to wolf scat. This indicates that ungulates
are able to recognize the risk of predation from predators with differing hunting modes based on
olfactory cues and adjust their anti-predatory behaviour.
Reducing competition by topping secondary stems may be an attractive alternative to traditional pre-commercial thinning in forestry, for both biological and financial reasons. In this study, the height development of secondary and main stems of birch (Betula pubescens Ehrh. and Betula pendula Roth, species not separated), and secondary stems of willow (Salix spp.) following such topping was examined in an even-aged and naturally regenerated stand in northern Sweden. At a main stem mean height of 2.8 m, the following treatments were applied to all secondary stems: top-breaking at 40 per cent (111 cm above ground) or 65 per cent (184 cm above ground) of main stem mean height. A control group (average height of secondary stems, 221 cm) was left untreated. Post-treatment damage to the trees was frequent for both genera. For birch, treatment rankings for all the secondary stems, and for undamaged secondary stems, according to height development after three growing seasons, were control ≥ top-breaking at 65 per cent ≥ top-breaking at 40 per cent. For willow, the greatest height growth was observed after top-breaking at 65 per cent. The results indicate that the 'stump height' (break-point) could be raised to a level of at least 65 per cent in this birch stand without risk of the main stems being overtopped. During the study period, 50 per cent of the main stems exchanged their leading shoots at least once.
The effects of fencing and site preparation on performance of birch (Betula pendula Roth), oak (Quercus robur L.), pine (Pinus sylvestris L.) and spruce [Picea abies (L.) Karst.] seedlings were studied over four growing seasons in southern Sweden. The experiment was composed of four browsing treatments, from which roe deer (Capreolus capreolus L.) were excluded for 0, 12, 24 or 42 months, and four soil treatments. Natural browsing was combined with artificial browsing (clipping). It was demonstrated that browsing by roe deer could be isolated from browsing by moose (Alces alces L.) by selective fencing. Except for birch, browsing had little effect on seedling survival. Browsing reduced height growth by more than 100% for oak and pine, and more than 60% of pine seedling developed multiple stems. Except for oak, site preparation increased seedling survival. Inverting site preparation, in combination with or without fertilization, produced positive growth responses in seedlings, whereas patch scarification did not. There was no interaction between browsing and soil treatments on seedling performance. It was concluded that long-term protection against browsing by roe deer is needed for oak and pine, whereas short-term fences might be used for birch, and that spruce is relatively unaffected by browsing.
Deciduous seedlings are valuable for the forest industry and, at the same time, often palatable for large herbivores. Therefore, browsing on seedlings of seven deciduous tree species and on Picea abies(L.) Karst., as a reference species, was tested in a field experiment with the species presented at feeding stations. Twenty stations, each with one seedling per species, were established in each of 15 clear-cuts in southern Sweden. The planting took place in October. Depending on species, between 16 and 85% of the seedlings were browsed after one winter. The descending order, based on number of browsed seedlings, was Quercus robur L . > Alnus glutinosa (L.) Gaertn.> Fagus silvatica L.> Tilia cordata Mill.> Prunus avium L.> Betula pendula Roth> Picea abies (L.) Karst. > Fraxinus excelsior L. On 83% (range 45-100%) of the browsed seedlings the leader was damaged. On average, browsing reduced seedling hight by 32% (range 12-47%). Within species, initially taller seedlings were more often selected than shorter ones.
The creation and restoration of natural woodland serving diverse socio-economic as well as nature conservation purposes has become a major objective of sustainable forestry throughout Europe. There is a main focus on the conversion of anthropogenous coniferous forests, which are widely spread in the Central European lowlands and mountain ranges, into natural broad-leaved forests. For ecological as well as economic reasons, the integration of natural regeneration processes into conversion management is considered an important task. Taking the woodland of the Menzer Heide (NE Germany), a typical Pleistocene landscape in the northern Central European lowlands as an example, a vegetation analysis of the Scots pine (Pinus sylvestris L.) plantations dominating in this area is presented. As the main results, (1) two communities are differentiated within the present-day pine plantations on the oligotrophic and acidic sandy soils. Indicated by different species compositions, the Dicranum-community and the Oxalis-community occur, the latter growing on sites with higher nutrient availability. (2) The comparison of an historical with the present vegetation analysis reveals an increase of nutrient availability in recent decades, most probably strongly related to the natural soil regeneration of the formerly exploited forest sites. (3) From the results of the vegetation analysis, including records of species and individual numbers of naturally rejuvenated trees, future stand development scenarios can be derived. Thus, the Oxalis-community may directly develop into oak-beech and beech stands as natural forests. In the long term, the Dicranum-community will pass a regeneration stage with pine and oak, probably further developing towards natural oak-beech and beech forests. In conclusion, decisions regarding extensive or intensive management, aiming at the conversion of coniferous plantations into natural broad-leaved forests, can be made following observation of the natural regeneration processes in the present-day stands. By utilising the natural regeneration processes and by applying only a few controlling silvicultural measures, a low-energy and cost-effective conversion of the forests can be accomplished.
Naturally regenerated 2- to 5-year-old pubescent birches (Betula pubescens Ehrh.) were cut monthly during 1983. Three 2–3 m high birches per month were cut with 0-cm and three with 10-cm high stumps in each of five blocks giving a total of 15 birches per stump height per month. The birches were located at Latitude 60° 15'N and Longitude 16° 00'E. Four-year-oldsilver birches (Betula pendula Roth) planted on a nursery field located at Latitude 60° 25'N and Longitute 14° 35'E were cut on 10 dates, between 19 June and 21 August 1986, with 10-cm high stumps. Four blocks with seven replications, totalling 28 stumps, per cutting period were used.
Cluster planting of oaks (Quercus robur and Quercus petraea) was introduced to central Europe in the 1980s and 1990s as an economic and ecological alternative to the traditional and costly row planting for re-afforestation of wind-thrown and clear-cut areas. Clusters comprising 20–30 seedlings are either ‘nests’ (nest planting) with very dense spacing of ca. 0.2 m between trees, or ‘groups’ (group planting) with 1 m between trees. Commonly, 100 groups or 200 nests ha−1 were planted in uniform distribution. We used a comprehensive weighted meta-analysis to compare the growth and quality (stem form, crown shape, branch free bole length, number of potential future crop trees) of oaks grown in clusters with those planted in rows (e.g. 2 × 1 m spacing). Data were obtained from 25 trials located in Germany, Switzerland and Austria. Tree survival, growth and quality were significantly lower in nests than in neighbouring row planting counterparts. Very low initial growing space was presumably one of the main reasons for low survival, unfavourable growth and quality development of oaks in nest plantings. In group plantings, survival, growth and tree quality were similar or superior to row plantings. Tree quality benefitted from the presence of trainer trees in group plantings. Based on this study, we recommend planting oak groups as an alternative to traditional row planting. Our study showed the usefulness of weighted meta-analysis to develop a synthesis from raw data collected from independent silvicultural trials established with comparable designs and similar research goals.
Topping, to reduce competition, may be an attractive alternative to traditional precommercial thinning in forestry for both biological and financial reasons. In this study, the height development of secondary and main stems of birch (Betula pubescens Ehrh. and Betula pendula Roth, species not separated), and secondary stems of willow (Salix spp.) was examined in a field experiment in northern Sweden. Treatments studied were: traditional precommercial thinning, topping at 40% of main stem mean height, topping at 70% of main stem mean height, and controls (untreated). Post-treatment damage to the trees was frequent for both genera, but especially for the willows. Treatment rankings for all of the secondary stems, and for undamaged secondary stems, according to height development after three growing seasons, were topping at 70% ≥ no treatment ≥ topping at 40% ≥ traditional precommercial thinning. The results also indicated that the cross-cutting level could be raised to a level of at least 40% of main stem height, without risking the main stems becoming overtopped. During the study period, 67% of the main stems exchanged their leading shoots at least once.
Topping, i.e. cutting or breaking the treetops of secondary stems, may be an attractive alternative to traditional precommercial thinning. The survival and height development of downy birch (Betula pubescens Ehrh.) after topping were examined over three growing seasons in two dense, naturally regenerated stands, 3.1–3.5 m high, in northern Sweden. The topping was performed in experiments with a two-factor randomized complete block design, as follows. Three treatments were applied to individual secondary stems (top-breaking at half the sample tree mean height, top-cutting at half the sample tree mean height, and traditional cutting just above ground) at each of three times: winter, spring and summer (in frozen, dormant and growing conditions, respectively). A control (no treatment) was also included. The survival rate was lowest for traditionally cut stems and for stems cut in growing conditions. Height development after three growing seasons was significantly affected by time of treatment, the height growth being lowest after treatment in growing conditions, but not by treatment. Height growth of control stems was not significantly different from height growth in any combination of treatment and time of treatment, after three growing seasons. However, control stems had the greatest leading shoot length in the third growing season.
While previous studies focused on tree growth in pure stands, we reveal that tree resistance and resilience to drought stress can be modified distinctly through species mixing. Our study is based on tree ring measurement on cores from increment boring of 559 trees of Norway spruce (Picea abies [L.] Karst.), European beech (Fagus sylvatica [L.]) and sessile oak (Quercus petraea (Matt.) Liebl.) in South Germany, with half sampled in pure, respectively, mixed stands. Indices for resistance, recovery and resilience were applied for quantifying the tree growth reaction on the episodic drought stress in 1976 and 2003. The following general reaction patterns were found. (i) In pure stands, spruce has the lowest resistance, but the quickest recovery; oak and beech were more resistant, but recover was much slower and they are less resilient. (ii) In mixture, spruce and oak perform as in pure stands, but beech was significantly more resistant and resilient than in monoculture. (iii) Especially when mixed with oak, beech is facilitated. We hypothesise that the revealed water stress release of beech emerges in mixture because of the asynchronous stress reaction pattern of beech and oak and a facilitation of beech by hydraulic lift of water by oak. This facilitation of beech in mixture with oak means a contribution to the frequently reported overyield of beech in mixed versus pure stands. We discuss the far-reaching implications that these differences in stress response under intra- and inter-specific environments have for forest ecosystem dynamics and management under climate change.
Question: What are the main driving factors in 70 years of natural dynamics in tree recruitment in the Białowieża National Park?Location: Białowieża National Park, Poland, is one of the least disturbed temperate, lowland forest systems in Europe.Methods: We tested whether fluctuations in large herbivore populations, changes in climate and openness of the forest explained compositional dynamics. Tree recruitment (to size class DBH≥5 cm) was measured on permanent transects (in total, 14.9 ha) six times between 1936-2002. These data were related to existing data on ungulate density, climatic parameters and estimates of forest openness collected during the same period.Results: Total recruitment of all tree species combined was negatively correlated with total ungulate density and red deer density. The variation in response between species was related to the preferences of herbivores; the more preferred forage species (especially Carpinus betulus) were positively and the less preferred species negatively related to herbivore density. Total tree recruitment rates were not related to climatic parameters and openness of the forest. Only Alnus glutinosa recruitment was significantly related to climatic parameters, and Ulmus glabra related to forest openness, but there were no predictable patterns in recruitment among species in relation to these factors.Conclusion: The present study indicated that changes in large herbivore density have played an important role in driving patterns in tree recruitment and species composition during the last 70 years in Białowieża National Park. In contrast to other studies, increasing herbivore numbers were associated with higher recruitment of preferred and browsing-tolerant species. Periodical crashes in ungulate numbers, whether human-induced or caused by natural factors, may offer windows of opportunity for regeneration of a range of tree species and facilitate more diverse and dynamic forest development.
For north-eastern Germany regional climate models project rising temperatures in combination with decreasing summer and increasing winter precipitation. The resulting overall drier conditions during the growing season will considerably impact forest growth there. We evaluate the consequences of increasing drought on the growth of the two locally most important broadleaf tree species common beech (Fagus sylvatica L.) and pedunculate oak (Quercus robur L.). Three mixed forests of beech and oak were sampled along a west-east gradient of declining precipitation. In total we used 257 ring-width samples from 133 trees to build six species and site specific chronologies. Additionally, we modelled the soil water budget for each site. We performed continuous and discontinuous (pointer year) analysis of climate-tree-growth relationships with particular emphasis on inter-annual-variations and their dependence upon climatic factors (temperature, precipitation, soil moisture) and on the stability of the obtained relationships. Results of climate-growth correlations together with pointer year analysis indicate a strong dependency of growth of both species from water availability, especially during early summer (June and July). General correlation pattern between growth and climate are similar for both species, but climate sensitivity of beech is generally higher. We identified drought as the main driver of negative growth depressions in both species. Increasing drought stress along the gradient is expressed in higher correlations to climatic variables, higher sensitivity (variance) of growth, and a higher number of negative pointer years for both species. For beech we also found a significant trend of decreasing average growth rates along the gradient. Growth superiority of beech compared to oak declines with decreasing precipitation. The relationships were generally stable throughout the 20th century. A rise of sensitivity together with a higher frequency of negative pointer years during the last decades suggests that increasing climatic variability together with rising temperatures might be influencing growth of Fagus at the more humid sites. If we substitute space by time it seems that already small changes in precipitation regime can have considerable impact, especially on the growth of beech. Other, more drought tolerant species like oak might gain competitive advantages under the projected climatic changes.Highlights► Dendrochronological investigations of beech and oak along precipitation gradient. ► Growth strongly depends on water availability especially during June and July. ► Sensitivity of tree growth and correlations to climate increase along gradient. ► Numbers of pointer years increase, changes more pronounced for beech. ► oak might gain competitive advantages under the projected drier climate.
The effect of cutting season on coppicing and growth of exotic (S. ‘Aquatica’, S. × dasyclados, S. riminalis) and local willows (S. phylicifolia, S. pentandra), and downy birch (B. pubescens) was studied in two experiments. At each of the 32–36 or 53 cutting times, 20–30 stools were cut down. Cutting of exotic willows at the end of July or beginning of August had a very detrimental effect on the survival, height growth and biomass production. Even though the height of local willows and downy birch was significantly shorter when cut during the growing period, their survival was not affected.Stump height (0, 10, 20 or 40 cm) affected markedly the biomass production of S. ‘Aquatica’ from the second rotation on. In the third rotation willows cut to 40-cm stump height yielded 68% less and those cut to 20-cm stump height 28% less than those cut to 10-cm stump height.Manual harvesting damage simulating the effects of harvesting machines had a negative effect on survival, height and biomass production in a young S. ‘Aquatica’ plantation. In older, well established plantations the effect was not significant. Differences between cutting methods were small.