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A Comparison of the Formation Rates and Composition of Tree-Related Microhabitats in Beech- Dominated Primeval Carpathian and Hyrcanian Forests
Abstract and Figures
Primeval forests in the temperate zone exist only as a few remnants, but theses serve as important reference areas for conservation. As key habitats, tree-related microhabitats (TreMs) are of intense interest to forest ecologists, but little is known about their natural composition and dynamics in different tree species. Beech forms a major part of the temperate forests that extend from Europe, home to European beech Fagus sylvatica L. (Fs), eastward to Iran, where Oriental beech Fagus orientalis Lipsky (Fo) is the dominant species. In this study, we compared TreMs in primeval forests of both species, using data from Fo growing in 25 inventory plots throughout the Hyrcanian forest belt in Iran and from Fs growing in a 9 ha permanent plot in the Uholka Forest of Ukraine. TreMs based on 47 types and 11 subgroups were recorded. Beech trees in the Hyrcanian forest had a higher mean diameter at breast height (dbh) than beech trees in Uholka and contained twice as many TreMs per hectare. Although the mean richness of TreMs per TreM bearing tree was similar in the two species, on the basis of the comparison single trees in two groups (n = 405 vs. 2251), the composition of the TreMs clearly differed, as the proportions of rot holes, root-buttress concavities, and crown deadwood were higher in the Hyrcanian Forest, and those of bark losses, exposed heartwood, and burrs and cankers higher in Uholka Forest. Estimates of TreMs dynamics based on dbh and using Weibull models showed a significantly faster cumulative increase of TreMs in Fo, in which saturation occurred already in trees with a dbh of 70-80 cm. By contrast, the increase in TreMs in Fs was continuous. In both species, the probability density was highest at a dbh of about 30 cm, but was twice as high in Fo. Because of limitations of our study design, the reason behind observed Forests 2020, 11, 144 2 of 13 differences of TreM formation and composition between regions remains unclear, as it could be either result of the tree species or the environment, or their interaction. However, the observed differences were more likely the result of differences in the environment than in the two tree species. Nevertheless, our findings demonstrate that the Hyrcanian Forest, recently designated as a natural heritage site in Iran, is unique, not only as a tertiary relict or due to its endemic trees, herbs and arthropods, but also because of its TreMs, which form a distinct and rich habitat for associated taxa, including endemic saproxylic species.
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... Our study provides references for the quantity and quality of TreMs in primeval mountain European beech forests. While several studies conducted to date have examined TreMs in forests dominated by European beech (Winter and Möller, 2008) (Kozak et al., 2018;Sever and Nagel, 2019;Jahed et al., 2020). However, the TreM density in the Bieszczady Mts. is higher than that in other parts of the Carpathians. ...
... TreM-bearing trees ha -1 ; Kozák et al., 2018) and in the Uholka Forests (106.2 TreM-bearing trees ha -1 ; Jahed et al., 2020). Furthermore, we found that the density of certain types/groups of TreMs varied between the studied regions. ...
... TreM-bearing trees ha -1 in Kozák et al., 2018 and 9.3 TreM-bearing trees ha -1 in Jahed et al., 2020) were lower than in other parts of the Carpathians. The reasons for the regional variation in TreM profiles in European beech-dominated forests is understudied, but could be the outcome of local climate, topography or disturbance regimes (Mráz and Ronikier, 2016;Kozak et al. 2018). ...
Tree-related Microhabitats (TreMs) are essential for sustaining forest biodiversity. Although TreMs represent ephemeral resources that are spread across the landscape, their spatial distribution within temperate forests remains poorly understood. To address this knowledge gap, we conducted a study on 90 sample plots (0.05 ha each) located in a primeval mountain European beech Fagus sylvatica -dominated forest (Bieszczady Mountains, Carpathians). We explored the TreM profile with its link to habitat characteristics and described the spatial distribution of TreM indices. We identified 61 TreM types, with a mean richness of 19.7 ±4.9 SD TreM types per plot, a mean density of 740.7 ±292.5 SD TreM-bearing trees ha ⁻¹ and a mean TreM diversity of 1.2 ±0.1 SD. The diameter and living status of trees (living vs dead standing tree) were correlated with TreM richness on an individual tree. The stand structure, i.e. density and/or basal area of living and/or dead standing trees, and topographic conditions, i.e. slope exposure, were correlated with the TreM richness, density and diversity recorded on a study plot. We found no relationship between TreM richness, density and diversity and the presence of canopy gaps, which indicates that the influence of small-scale disturbances on the TreM profile is limited. However, our analysis revealed a clustered spatial pattern of TreM indices, with TreM-rich habitat patches (hot-spots) covering ∼20% of the forest. A moderate TreM richness, density and diversity dominated ∼60% of the forest, while TreM-poor habitat patches (cold-spots) covered ∼20%. Based on our findings, we advise the transfer of knowledge on the spatial distribution of TreMs from primeval to managed forests and advocate the ‘2:6:2’ triad rule: to allocate 20% of forests as strictly protected areas, to dedicate 60% to low-intensity forest management with the retention of large living trees and all dead standing trees, and to use the remaining 20% for intensive timber production. To ensure the continuance of the majority of TreM types, ≥ 55 living trees ha ⁻¹ > 60 cm in diameter should be retained. Such an approach will maintain a rich and diverse TreM assemblage across a broad spatial scale, which in turn will support biodiversity conservation and ecosystem restoration in secondary or managed forests.
Highlights
Primeval mountain beech forest hosts rich and abundant TreM assemblage
Stand structure, slope exposure, but not canopy gaps mould TreM profiles
Habitat patches with high/low TreM indices are spatially clustered
Hot- and cold-spots each make up 20% of TreM richness, density and diversity
2:6:2 - the protected: managed forest ratio for maintaining the TreM assemblage
... The profiles of TreMs expected to be near-natural have to date been investigated mainly in relatively small patches of mountain forests that used to be felled for timber but now enjoy long-term strict protection (Jahed et al., 2020;Kozák et al., 2018;Michel and Winter, 2009). Although primeval forests are an irreplaceable source of reference data (Jaroszewicz et al., 2019), the TreMs in such pristine conditions in the temperate zone remain largely unrecognized (Asbeck et al., 2022), as the lowland primeval forests of the northern hemisphere have gradually disappeared over the centuries (Sabatini et al., 2018). ...
... Although the density of woodpecker cavities was much lower (20.0 TreM-bearing trees ha − 1 ) than the pooled density of all cavity groups formed as a result of wood decomposition (119.6 TreM-bearing trees ha − 1 ) (see Table 2), the density of the TreM group of vertebrate origin in BF was from 50 % (13.3 TreM-bearing trees ha − 1 ) (Kozák et al., 2018) to 2122 % (0.9 TreMbearing trees ha − 1 ) (Jahed et al., 2020) greater than in primeval mountain beech forests. In addition, the pooled density of woodpecker cavities, trunk and mould cavities and branch holes (139.6 TreMbearing trees ha − 1 ) (see Table 2) was 93 % higher in BF than the pooled density of these TreM groups found in riparian forests, previously considered to be cavity-rich (72.2 TreM-bearing trees ha − 1 ) (Przepióra and Ciach, 2022). ...
... Moreover, the typologies used in previous studies may contain different criteria for assigning certain TreMs. For example, some studies were based on typologies which did not contain any criteria for cavity dimensions (Larrieu et al., 2012), or else cavities were distinguished on the basis of their general size, i.e. small/medium/large (Jahed et al., 2020). Some studies were based on the same typology, but the detailed descriptions of specific TreM criteria were modified (Marziliano et al., 2021;Winter and Möller, 2008). ...
Tree-related Microhabitats (TreMs) are a key structural element having a significant impact on the biodiversity and functioning of forest ecosystems. Although forests enjoying long-term protection host richer and more abundant TreMs compared to managed stands, the quantity and quality of such microstructures in primeval temperate forests are unknown. This study investigates for the first time the assemblage of TreMs in the Białowieża Forest (BF), which is regarded as the last surviving fragment of pristine lowland forests in the temperate zone of Europe. Relatively undisturbed by human activity since the last glacial period, the BF ecosystem has remained remarkably intact, which may have given rise to its unique TreM assemblage. Here, we show that a primeval forest is characterized by an exceptionally high richness and density of TreMs compared to previously studied natural forests, and that the richness, density and diversity of TreMs are spatially heterogeneous at the micro-scale but homogeneous at the macro-scale. This indicates that adjacent small fragments of habitat (0.05 ha) may have different TreM profiles, but large patches of forest (several ha) host similar assemblages of TreMs. Our profile of TreMs depends on the basal area and density of living trees, the basal area of dead standing trees and the dominance of specific TreM-hosting tree species in a stand. Our study suggests that both the ecological continuity and complexity of a forest supporting many different tree species and the diversity of TreM-forming biota that typically occurs in primeval temperate forests are factors that appear to contribute to the observed profile of TreMs. The results of our study set a benchmark for the quantity and quality of TreMs in broadleaved temperate forests and indicate that the long-term spontaneous natural processes occurring in primeval forests lead to the emergence of ultra-rich, complex assemblages of TreMs.
... While many TreM studies have been conducted in beech forests, most were at a local or regional scale and were restricted to either F. sylvatica or F. orientalis, a particular elevation, or a particular climate. Their results Courbaud et al., 2017;Jahed et al., 2020;Winter et al., 2015) are therefore strongly context dependent and difficult to transfer to other regions. Only one study based on extensive data collection investigated the role of DBH and management on the rate of TreM formation in European and Oriental beech (Courbaud et al., 2021). ...
... H2: TreM assemblages at the stand scale are driven by (H2a) management, (H2b) elevation, and (H2c) the number of admixed tree species. H3: TreM diversity and composition differ generally between the two Fagus species as shown locally by Jahed et al. (2020). ...
... However, since they represent only a small part of the tree population, conservation issues focused on TreM-dwelling taxa need to focus on the dominant tree species. The previous studies comparing European and Oriental beech for TreM supply (Courbaud et al., 2021;Jahed et al., 2020) used unpaired sampling design and investigated only relatively few individual trees for Oriental beech (371 and 405 respectively). In addition, we took account of unobserved TreMs, a statistical method that has never been used before and that proved effective. ...
Tree-related microhabitats (TreMs) provide a quantitative indicator of habitat heterogeneity in forests, including beech (Fagus) forests. However, systematic analyses of the factors driving TreM diversity and composition in Fagus sylvatica and F. orientalis forests are lacking. In this study, the TreMs of beech forests on 203 plots of 22 forest sites (production and old-growth forest) across the full longitudinal range of both species were assessed following a standardized TreM protocol. A unified diversity and ordination framework based on Hill numbers was applied to account for unobserved TreM types and to extend the sensitivity of our findings focusing from rare to dominant TreMs. The composition of TreM assemblages was mostly determined by Fagus species and elevation, a surrogate for climate, and with focus on dominant TreMs by DBH, whereas old-growth versus production forest had no effect. The coverage of detected TreMs per plot increased with the number of trees assessed and DBH, but was lower in old-growth than in production forests. When standardized for sampling * Corresponding author at: Field Station Fabrikschleichach, 2 coverage, the diversity of rare and dominant TreM types was higher in old-growth than in production forests, but increased with elevation only focusing on dominant TreMs. These findings corroborate regional studies showing a higher TreM diversity in old-growth forests. Moreover, they demonstrate the importance of focusing conservation efforts on forests of both Fagus species and at different elevations, covering the full range of TreM assemblages. Future studies comparing TreM diversity in different forests should standardize diversity by sample coverage, as currently done in many biodiversity studies.
... forests have however been conducted in recent years (Asbeck et al., 2020a;Jahed et al., 2020). In line with these efforts, this article conducts a systematic review of the scientific literature on TreMs to identify research gaps, for example in terms of geographical coverage or themes. ...
... A wide diversity of terms, however, has been used to refer to TreMs before the terminology became more homogenized in recent years. We therefore relied on the literature already known by the authors to identify the different terms that have been used to refer to TreMs, here presented in the singular form: TreM (Jahed et al., 2020), tree related microhabitat , tree microhabitat (Paillet et al., 2015), bark microhabitat (Michel et al., 2011), microhabitat (Winter and Möller, 2008), microhabitat-bearing tree (Regnery et al., 2013b), dendromicrohabitat (Madera et al., 2017), special tree structure (Winter et al., 2005) or structural diversity characteristic (Lilja and Kuuluvainen, 2005). We used wildcards ( * ) to account for various word spellings. ...
... Overall, larger and senescent or dead tree are more likely to bear many TreMs (e.g., Michel et al., 2011;Paillet et al., 2019;Asbeck et al., 2021b;Kõrkjas et al., 2021b;Martin et al., 2021b;). For a same diameter at breast height, hardwoods tend to present a higher number and diversity of TreMs Bouget et al., 2014a;Paillet et al., 2019;Jahed et al., 2020;Asbeck et al., 2021b;Marziliano et al., 2021). At the stand scale, we generally observe the higher TreMs richness and diversity in old and "natural" (i.e., either old-growth, primary or intact) forests (9.9% of the corpus; Table 3) or formerly managed forests untouched over several decades (16.8% of the corpus; Table 3) compared to younger and managed forests. ...
Sustainable management of forest ecosystems requires the use of reliable and easy to implement biodiversity and naturalness indicators. Tree-related microhabitats (TreMs) can fulfill these roles as they harbor specialized species that directly or indirectly depend on them, and are generally more abundant and diverse in natural forests or forests unmanaged for several decades. The TreM concept is however still recent, implying the existence of many knowledge gaps that can challenge its robustness and applicability. To evaluate the current state of knowledge on TreMs, we conducted a systematic review followed by a bibliometric analysis of the literature identified. A total of 101 articles constituted the final corpus. Most of the articles (60.3%) were published in 2017 or after. TreM research presented a marked lack of geographical representativity, as the vast majority (68.3%) of the articles studied French, German or Italian forests. The main themes addressed by the literature were the value of TreMs as biodiversity indicators, the impact of forest management on TreMs and the factors at the tree- and stand-scales favoring TreMs occurrence. Old-growth and unmanaged forests played a key role as a “natural” forest reference for these previous themes, as TreMs were often much more abundant and diverse compared to managed forests. Arthropods were the main phylum studied for the theme of TreMs as biodiversity indicators. Other more diverse themes were identified, such as restoration, remote sensing, climate change and economy and there was a lack of research related to the social sciences. Overall, current research on TreMs has focused on assessing its robustness as an indicator of biodiversity and naturalness at the stand scale. The important geographical gap identified underscores the importance of expanding the use of the TreMs in other forest ecosystems of the world. The notable efforts made in recent years to standardize TreM studies are an important step in this direction. The novelty of the TreM concept can partially explain the thematic knowledge gaps. Our results nevertheless stress the high potential of TreMs for multidisciplinary research, and we discuss the benefits of expanding the use of TreMs on a larger spatial scale.
... Few studies have sought to separate tree age and DBH effect on TreM development (Kõrkjas et al., 2021a ;Kozák et al., 2023). In congruence with numerous studies (Jahed et al., 2020;Paillet et al., 2019;Spînu et al., 2022), the tree-level TreM abundance and richness increased with increased tree size and TreM groups associated with increased surface area (rot-holes, crown deadwood, epiphytes) ...
Retention of structural elements such as deadwood and habitat trees at the level of forest stands has been promoted to integrate biodiversity conservation into multiple-use forest management. The conservation value of habitat trees is largely determined by the presence, richness, and abundance of tree-related microhabitats (TreMs). Since TreMs are often lacking in intensively managed forests, an important question of forest conservation is how the abundance and richness of TreMs may be effectively restored. Here, we investigated whether the strict protection of forest through cessation of timber harvesting influenced TreM occurrence at tree and stand levels. For that purpose, we compared four managed and four set-aside stands (0.25 ha each) in the Białowieża Forest, with identical origin following clear-cuts approximately 100 years ago. We found that the abundance and richness of TreMs on living trees were not significantly different between stands that were either conventionally managed or where active forest management ceased 52 years ago. Yet, our analysis of TreMs on tree species with contrasting life-history traits revealed that short-lived, fast-growing species (pioneers) developed TreMs quicker than longer-lived, slower-growing species. Hence, tree species such as Populus or Betula, which supply abundant and diverse TreMs, can play an important role in accelerating habitat restoration.
... In the primary European beech-dominated forests of the Carpathians and Dinaric mountains an average TreM-Abundance of 482.9 TreMs per hectare was found (Kozák et al. 2018). European beech (Fagus sylvatica) trees in primeval forests in Ukraine had a mean of 2 TreMs per beech tree (Jahed et al. 2020). An average richness of 3 TreMs per living tree was reported for the primary forests of the Western and Southern Carpathians ). ...
The individual or grouped retention of habitat trees in managed multiple-use forests has become an approach used to protect biodiversity-related structural attributes typically found in old close-to-nature forests. This study focuses on the effect of one such retention approach in the managed forests of Baden-Württemberg, Germany, ten years after its introduction. Specifically, we asked: (1) How effective are habitat tree groups (HTGs) at providing large living trees (LLTs > 80 cm DBH), tree-related microhabitats (TreMs), and dead wood?, and (2) which tree and stand variables have the greatest influence on the occurrence of TreMs? For this purpose, we inventoried 326 HTGs and 94 reference plots in forests dominated by the most widely occurring native conifer and broadleaf tree species, silver fir (Abies alba) and European beech (Fagus sylvatica). In accordance with our hypotheses, LLTs and TreMs were significantly more abundant in HTGs than in reference plots in both forest types. More importantly, when retaining 5% of the forest area as HTGs (a common retention level), old forest attributes such as woodpecker cavities, rot-holes or exposed heartwood increased significantly at the stand level while the volume of LLTs almost tripled, and volume of snags increased by 25%. However, quantities of these two attributes remain below minimum thresholds recommended in the scientific literature. A conversion of 15–25% of the stand area into HTGs is needed to increase the stand level abundance of TreMs such as concavities, exposed sapwood, or crown dead wood significantly in the short term. At the single-tree level, tree diameter (DBH), tree species, vitality and neighborhood competition had a significant influence on modeled TreM abundance. At the stand level, TreM occurrence increased with stand age and amount of snags, whereas TreM richness declined with stand density. Ten years after introducing the retention approach, forest stands with HTGs comprised significantly more important structural attributes than those without. Selecting HTGs with high stand volume or low tree density that also include snags, a mix of tree species, LLTs, and some low-vitality habitat trees could further improve this practice.
... Investigating TreM occurrences in forests that have never been managed or have not been managed for a long time provides a significant reference for understanding patterns of TreM development under natural conditions. Thus, primary forests represent the ultimate intact habitat (Ulyshen et al., 2018) for biodiversity studies because they often contain an abundant and diverse array of TreMs (Asbeck et al., 2021b;Jahed et al., 2020;Kozák et al., 2018;Larrieu et al., 2014). ...
Protecting structural features, such as tree‐related microhabitats (TreMs), is a cost‐effective tool crucial for biodiversity conservation applicable to large forested landscapes. Although the development of TreMs is influenced by tree diameter, species, and vitality, the relationships between tree age and TreM profile remain poorly understood. Using a tree‐ring‐based approach and a large data set of 8038 trees, we modeled the effects of tree age, diameter, and site characteristics on TreM richness and occurrence across some of the most intact primary temperate forests in Europe, including mixed beech and spruce forests. We observed an overall increase in TreM richness on old and large trees in both forest types. The occurrence of specific TreM groups was variably related to tree age and diameter, but some TreM groups (e.g., epiphytes) had a stronger positive relationship with tree species and elevation. Although many TreM groups were positively associated with tree age and diameter, only two TreM groups in spruce stands reacted exclusively to tree age (insect galleries and exposed sapwood) without responding to diameter. Thus, the retention of trees for conservation purposes based on tree diameter appears to be a generally feasible approach with a rather low risk of underrepresentation of TreMs. Because greater tree age and diameter positively affected TreM development, placing a greater emphasis on conserving large trees and allowing them to reach older ages, for example, through the establishment of conservation reserves, would better maintain the continuity of TreM resource and associated biodiversity. However, this approach may be difficult due to the widespread intensification of forest management and global climate change.
Tree-related microhabitats (TreMs) have been promoted as indicators of forest biodiversity and to guide conservation practices. Ensuring the provision of diverse TreMs in the long term is crucial for the survival of many forest-dwelling species. Yet, this task is challenging in the absence of information regarding TreM dynamics. We analysed the temporal development of TreMs on 11,569 living trees in temperate European forests. To identify drivers of change in TreM abundance and richness over a period of 3–12 years, we estimated the rates of TreM persistence and loss events at the tree-level using survival analysis methods: persistence was characterised by consistency and increment events (when TreM numbers were maintained or increased) and loss was defined as a reduction in TreM numbers or their disappearance. Stratified Cox proportional hazards models were fitted for different TreM groups. Our study revealed a highly dynamic TreM development on living habitat trees, particularly on large trees. While specific TreMs are prone to disappearing, irrespective of tree species or TreM groups, total TreM richness persists over a 12-year period. TreMs such as crown deadwood, epiphytes or woodpecker cavities are prone to decrease in the long term. However, large trees were more likely to maintain a certain degree of TreM richness. Increasing diameters resulted in high persistence rates in seven TreM groups and concomitantly low loss rates in four of them (exposed sap- and heartwood, concavities). Selecting habitat trees based on TreMs should consider the likelihood of TreMs being lost over time, to ensure the long-term provision of microhabitats for associated species.
Graphical Abstract
The present study aims to evaluate the effect of single-tree selection harvest intensity on biomass of
hornbeam-Persian ironwood stand. For this purpose, information on all trees and dead trees were
collected in 70 half-hectare plots. The 35 sample plots were in single-tree selection stands with three
harvest intensities and the same sample plots were in control stand. Trees litter fall were measures from
September to February and the storage of soil organic carbon was determined through organic carbon
and bulk density. Then, tree biomass, litter biomass, dead tree biomass and total biomass were finally
calculated. The results showed with increasing the rate of harvest intensity up to 13.5% the total biomass
had rising trends, although harvest intensity had no significant effect on aboveground and belowground
biomass and soil organic carbon. The aboveground biomass was higher in single-tree selection stand
than control stand. The average of total biomass was 147 and 144 ton/ha in harvest and control
hornbeam-Persian ironwood stands respectively and harvesting increased two percent of mean total
biomass. The medium harvest intensity (3.6-9.5% of stand volume) was finally determined as
appropriate selective logging intensity. The correspondence of litter biomass and dead tree biomass as
bio indicator indicated that tree marking in the single-tree selection system was advisable.
Background and Objectives:
In recent years the protection of biodiversity became an important goal in forest management and caused some conservativem management approaches such as creating protected areas or areas in which no management has been implemented. In the last decade, habitat trees came under focus. Micro habitats are structures on dead or alive trees in the forest including changes such as wounds and fractures caused by biological processes and provide places for forest living organisms. Nowadays the necessity of habitat tree protection has been emphasized in forest management and policies. This study aimed to assess the diversity and frequency of tree micro habitats in Persian ironwood- hornbeam forest stands at Bahramnia Forestry Plan (Gorgan).
Materials and Methods:
Therefore for assessing the trees’ micro-habitats 4 square sample plots each one with an area of 2500 m2 were selected and allometric characteristics (diameter and height) of all trees with a diameter more than 7.5 cm were recorded. Then according to an instruction the type and abundance of micro-habitats were assessed and recorded for all trees. A binocular was used for assessing the micro-habitats located on top of the tree crown and their upper trunk. The habitat value, as well as the economic value of all trees, have been calculated. A correlation test was used to assess the relationship between occurrence and frequency of micro-habitat with quantitative characteristics of all trees.
Results:
The result showed that the studied stand is an uneven-aged stand and the Persian-ironwood tree species is the most abundant tree species within it. The hornbeam trees have the highest average diameter and height, as well as the highest diversity and frequency of micro habitats. The most frequent micro-habitats observed on the trees were EP, GR, and CV. The result of the correlation test showed a significant relationship between tree diameter and micro-habitat abundance. By increasing the tree diameter the number of micro-habitats significantly increased.
Conclusion:
Totally the results of this study show that there are different kinds of micro-habitats in the studied forest stands. Also, the tree diameter is one of the factors that affect micro-habitat abundance. Therefore it is of importance to maintain some of the high diameter trees in the forest stand. Understanding the effective factors on occurrence and abundance of the micro-habitats can be an important help in protecting forest biodiversity.
Retention forestry implies that biological legacies like dead and living trees are deliberately selected and retained beyond harvesting cycles to benefit biodiversity and ecosystem functioning. This model has been applied for several decades in even-aged, clearcutting (CC) systems but less so in uneven-aged, continuous-cover forestry (CCF). We provide an overview of retention in CCF in temperate regions of Europe, currently largely focused on habitat trees and dead wood. The relevance of current meta-analyses and many other studies on retention in CC is limited since they emphasize larger patches in open surroundings. Therefore, we reflect here on the ecological foundations and socio-economic frameworks of retention approaches in CCF, and highlight several areas with development potential for the future. Conclusions from this perspective paper, based on both research and current practice on several continents, although highlighting Europe, are also relevant to other temperate regions of the world using continuous-cover forest management approaches.
Electronic supplementary material
The online version of this article (10.1007/s13280-019-01190-1) contains supplementary material, which is available to authorized users.
Dead wood (DW) provides critical habitat for thousands of species in forests, but its amount, quality and diversity have been heavily reduced by forestry. Therefore, interventions aiming to increase DW might be necessary to support its associated biodiversity, even in protected forests, which may be former production forests. Our aim was to synthesize the current state of knowledge drawn from replicated experimental studies into solid quantitative evidence of the effects of DW manipulation on forest biodiversity, with a focus on protected forests.
We conducted a full systematic review of effects of DW manipulation on forest biodiversity in boreal and temperate regions. We included three intervention types: creation of DW from live trees at the site, addition of DW from outside the site and prescribed burning. Outcomes included abundance and species richness of saproxylic insects, ground insects, wood‐inhabiting fungi, lichens, reptiles and cavity‐nesting birds. In total, we included 91 studies, 37 of which were used in meta‐analyses.
Although meta‐analysis outcomes were heterogeneous, they showed that increasing the amount of DW (“DW enrichment”) has positive effects on the abundance and richness of saproxylic insects and fungi. The positive effect on saproxylic pest insect abundance tended to be less than that on saproxylic insects in general. No significant effects were found for ground insects or cavity‐nesting birds.
Although reviewed studies were mainly short term, our results support that management that increases DW amounts has the potential to increase the abundance of DW‐dependent species and, in most cases, also their species richness. Studies of burning showed positive effects on the abundance of saproxylic insects similar to those of other interventions, even though burning on average resulted in a smaller enrichment of DW amounts.
Policy implications. The findings of the review suggest that manipulating dead wood (DW) can be an effective part of conservation management to support biodiversity in protected areas. The findings also indicate that the diversity of DW types is important, a mix of DW qualities should be favoured. Burning seems to be an effective method to increase biodiversity but to benefit cavity‐nesting birds, snag losses need to be minimized.
International conventions and resolutions on biological diversity, sustainable forest management and climate change have led in recent decades to an increasing interest in having reference values from forests undisturbed by man. An outstanding example of such an undisturbed forest is the primeval forest of Uholka-Shyrokyi Luh within the Carpathian Biosphere Reserve (Ukraine). It is approximately 9000 ha (90 km2) in area and is thought to be the largest primeval forest of almost pure European beech (Fagus sylvatica L.). In 2010, the Swiss Federal Institute for Forest, Snow and Landscape Research WSL, the Ukrainian National Forestry University UNFU and the Carpathian Biosphere Reserve CBR carried out a sampling inventory of the Uholka-Shyrokyi Luh forest (survey perimeter 10?282 ha) to obtain representative data for the main forest parameters. Given the remoteness of the area, long walking distances and difficult terrain, careful planning and organisation were required, as well as the logistic support of the local forest service. The field work was carried out by six mixed teams of Swiss and Ukrainian students and scientists, guided by three survey leaders from Switzerland and Ukraine. Two teams together shared a leader and a cook, and lived in decentralized camps, which were moved every week to minimize the walking needed to reach the sample plots. The collaboration between the Ukrainians and Swiss worked very well and was enriching for both sides. During the two-month sampling period, the teams assessed 314 sample plots laid out on a systematic grid. All living and standing dead trees = 6 cm DBH (diameter at 1.3 m above ground) within the 500 m2 circle plots were measured and assessed for features relevant for biodiversity. Lying deadwood was assessed with line-intersect sampling (3 lines each 15 m long per plot), and small trees (= 10 cm height and < 6 cm DBH) were surveyed on subplots consisting of three concentric circles 5, 10 and 20 m2 in area. The stand structure and any traces of anthropogenic use were assessed on a circular interpretation area of 2500 m2 around the sample plot centre. The primeval forest of Uholka-Shyrokyi Luh shows all the typical features of an old-growth forest shaped by small-scale disturbances. The structure was mainly three-layered, and most of the gaps encountered were not larger than the crown of a canopy tree. The growing stock per ha was 582 (± 14) m3 (mean ± standard error) and the deadwood volume 163 (± 8) m3. The ratio of standing to lying deadwood was 1:?5. The maximum DBH measured was 150 cm, and 10 trees per ha had a DBH of at least 80 cm. The density of habitat trees, i.e. living trees with features such as cracks, holes, bark damage or similar that provide microhabitats, was 150 (± 8) per ha (35?% of the living trees). Of all the trees recorded, 97?% were beech, although 14 other tree species were identified. All species found in the tree population = 6 cm DBH were also present in the regeneration. Traces of human presence were encountered on 19?% of the assessed plots (interpretation areas), mainly in the buffer and regulated protection zone of the protected massif. Most of these traces do not affect the integrity and pristine character of the forest. Nevertheless, they imply a certain pressure exerted from the nearby settlements and from the mountain pastures. The data obtained provide good reference values for old-growth beech forests and a valuable basis for more detailed analyses and comparisons with other old-growth and managed forests. The inventory was carried out and documented in a replicable way, and can thus be repeated if desired. The plots may also be used for other non-destructive studies, e.g. on fungi.
In Central European temperate forests, the host tree identity is one factor that determines the diversity of saproxylic organisms. These forests have been affected by humans for millennia, in contrast to the Hyrcanian forests south of the Caspian Sea, with their numerous old-growth features and endemic species. How the tree host species in this temperate relict of Tertiary forests affects saproxylic biodiversity is unknown, as an inventory of the saproxylic fauna present is incomplete, and new species are still being described. To analyze the importance of four dominant tree species in this region (Fagus orientalis, Quercus castaneifolia, Alnus subcordata, and Carpinus betulus), we sampled saproxylic beetles and true bugs with flight-interception traps at five dead trees per host species. We identified 361 beetle and 7 true bug species; of these, 268 were saproxylic, 56 were endemic, 11 were Central European “primeval-forest relicts”, and at least 16 species were undescribed. Rarefaction-extrapolation curves indicated higher species richness of saproxylic beetles and true bugs on F. orientalis and C. betulus than on A. subcordata and Q. castaneifolia, but ordination showed that communities were most distinct on Q. castaneifolia. Higher species richness on C. betulus and F. orientalis compared to Q. castaneifolia was unexpected based on literature but is in line with recent findings of experimental studies from Central Europe. Our results underline previous findings on the importance of moribund trees and dead wood in the Hyrcanian forests, and thereby support current efforts of Iranian authorities to stop the removal of veteran trees. The complementary fauna on oak trees compared to the other three tree species illustrates the importance of fragments of the almost destroyed oak forests along the coastline for forest biodiversity conservation in the Hyrcanian region.
Dead wood is a habitat for numerous fungal species, many of which are important agents of decomposition. Previous studies suggested that wood‐inhabiting fungal communities are affected by climate, availability of dead wood in the surrounding landscape and characteristics of the colonized dead‐wood object (e.g. host tree species). These findings indicate that different filters structure fungal communities at different scales, but how these factors individually drive fungal fruiting diversity on dead‐wood objects is unknown.
We conducted an orthogonal experiment comprising 180 plots (0.1 ha) in a random block design and measured fungal fruit body richness and community composition on 720 dead‐wood objects over the first 4 years of succession. The experiment allowed us to disentangle the effects of the host (beech and fir; logs and branches) and the environment (microclimate: sunny and shady plots; local dead wood: amount and heterogeneity of dead wood added to plot).
Variance partitioning revealed that the host was more important than the environment for the diversity of wood‐inhabiting fungi. A more detailed model revealed that host tree species had the highest independent effect on richness and community composition of fruiting species of fungi. Host size had significant but low independent effects on richness and community composition of fruiting species. Canopy openness significantly affected the community composition of fruiting species. By contrast, neither local amount nor heterogeneity of dead wood significantly affected the fungal diversity measures.
Synthesis . Our study identified host tree species as a more important driver of the diversity of wood‐inhabiting fungi than the environment, which suggests a host‐centred filter of this diversity in the early phase of the decomposition process. For the conservation of wood‐inhabiting fungi, a high variety of host species in various microclimates is more important than the availability of dead wood at the stand level.
A central hypothesis of ecology states that regional diversity influences local diversity through species-pool effects. Species pools are supposedly shaped by large-scale factors and then filtered into ecological communities, but understanding these processes requires the analysis of large datasets across several regions. Here, we use a framework of community assembly at a continental scale to test the relative influence of historical and environmental drivers, in combination with regional or local species pools, on community species richness and community completeness. Using 42,173 vegetation plots sampled across European beech forests, we found that large-scale factors largely accounted for species pool sizes. At the regional scale, main predictors reflected historical contingencies related to post-glacial dispersal routes, whereas at the local scale, the influence of environmental filters was predominant. Proximity to Quaternary refugia and high precipitation were the main factors supporting community species richness, especially among beech forest specialist plants. Models for community completeness indicate the influence of large-scale factors, further suggesting community saturation as a result of dispersal limitation or biotic interactions. Our results empirically demonstrate how historical factors complement environmental gradients to provide a better understanding of biodiversity patterns across multiple regions.
Aim
Beech forests comprise a globally unique temperate forest type in Europe. The dominance of beech in these forests developed during the ongoing post‐glacial northward re‐colonization, concurrently with intensified forest use by humans. We investigated how these two processes together with climate shaped the patterns of functional diversity of two major species groups involved in wood decomposition and whether functional diversity is determined on the local or regional species pool level.
Location
European beech forest distribution range.
Taxon
Saproxylic beetles and fungi.
Methods
We analysed records of 532,496 saproxylic beetles of 788 species and 8,630 records of 234 saproxylic fungal species based on sets of traits similar to both groups. We tested how space, climate and landscape composition affect trait‐based functional diversity on local and regional scales. Using structural equation modelling, we tested whether functional diversity is shaped on the local or regional scale.
Results
The response of local functional diversity of both saproxylic beetles and fungi followed a highly congruent pattern of decreasing functional diversity towards the north, with higher elevation and accounted for overall geographical gradients with higher temperature, while increasing with higher precipitation. Structural equation modelling revealed that local functional diversity is determined by community changes operating on the level of the regional species pool.
Main conclusions
Our findings suggest that the functional diversity patterns of saproxylic organisms in European beech forests are mainly determined on the regional scale and driven by anthropogenic and biogeographical processes. To conserve the variation and hotspots of functional diversity in beech forests, activities have to focus on a broad spatial and climatic range of sites throughout Europe, including the primeval forests in the east, as started by the UNESCO World Heritage selection of “Ancient and Primeval Beech Forests of the Carpathians and Other Regions of Europe”.
Integrative management strategies that simultaneously aim for wood production and biodiversity conservation are considered crucial to protect biodiversity of forest species outside protected areas. In this study, we evaluated whether deadwood enrichment as an integrative strategy at a scale of 17,000 ha resulted in enhanced biodiversity of saproxylic and non-saproxylic taxa eight years after the implementation of the strategy. The strategy included active deadwood enrichment with harvest remnants, retention of deadwood, and nature forest reserves areas. The analysis was based on data on the occurrence of plants, fungi, beetles, true bugs and birds from directly before and after the implementation of the strategy. The implementation of the strategy resulted in an increase in the deadwood amount by an average of 90 ± 40 m³ ha⁻¹ (mean ± SE) over this period. While deadwood amounts doubled in production forests (+90%), they increased even more in nature forest reserves (+160%). Multidiversity (species density of all taxa) increased with an increase in deadwood amount; this was a result of an increase in the multidiversity of saproxylic species as the non-saproxylic multidiversity did not respond. Among single taxon groups, fungal and beetle species density responded positively to the increase in deadwood amount, especially when only saproxylic species were analysed. Importantly, this effect was not only found in the nature forest reserves, but also in the production forests. We thus conclude that active deadwood enrichment in production forests and nature forest reserves is a promising tool to rapidly promote the protection of forest biodiversity.
Aim
The Rosalia longicorn ( Rosalia alpina ) is an internationally protected icon of biodiversity associated with old trees and dead wood. Although the beetle regularly exploits several marginal hosts, its preferred main host is European beech ( Fagus sylvatica s.l.). Moreover, the geographical ranges of R. alpina and beech closely overlap. To assess whether their spatial association is mirrored in the genetic patterns of both species, we investigated the phylogeography of Rosalia alpina over its entire geographical range and compared it with the known genetic patterns of its hosts.
Location
Europe and western Asia.
Methods
Using both mitochondrial ( COI ) and nuclear (14 microsatellite loci) markers, we analysed 148 (444, respectively) individuals from 31 (30, respectively) sites. We constructed a Bayesian Inference tree and a haplotype network, calculated the spatial analysis of molecular variance and assessed the population structure of our dataset using two Bayesian clustering methods ( STRUCTURE and BAPS ).
Results
Mitochondrial markers suggested existence of five clades in R. alpina populations. Two of them were endemic to the Italian mainland, one to Sicily, and another to southern Turkey. The remaining clade probably originated in the Balkans and colonized the rest of the species’ range. Nuclear markers supported this division. They also suggested two main recolonization routes from the Balkans; one heading north and then both west and east, the second expanding eastwards as far as the Caucasus. The observed genetic patterns were largely congruent with those of European beech.
Main conclusions
The results of both markers were mostly congruent, suggesting at least four potential refugia for R. alpina located in the southernmost parts of its geographical range. Its populations from a large part of Europe and western Asia, however, were genetically poor, dominated by a single haplotype. Phylogeographies of the beetle and its main host seem to be tightly matched, reflecting their common history.
The continued provision of old-growth elements in forest landscapes is a critical factor for biodiversity conservation in Central Europe. A well-established method for predicting the potential of forests to maintain biodiversity is to quantify tree-related microhabitat structures (TreMs). Our aim was to predict the TreM abundance and diversity for collectives of TreM-bearing trees; here 15 large trees per plot that were preselected by the largest crown sizes using remote sensing information. TreMs were inventoried on 2085 living trees across 139 plots (each 1 ha) in montane forests of the Black Forest, southwest Germany according to a detailed catalogue comprising 64 different TreM structures. We tested the influence of forest management, forest cover in the surrounding landscape (25 km radius), forest type, the number of standing dead trees, altitude and mean diameter at breast height (DBH) on the abundance and diversity of TreMs on living trees. All plots are managed or have been recently (20-40 yrs) abandoned from management. Generalized linear models (GLM) were used to identify the drivers of abundance and diversity of TreMs. The abundance of TreMs borne by the 15 large trees per plot is greater on plots located at higher altitudes. Increasing mean DBH leads to significantly higher abundance and diversity of TreMs. Groups of TreM-bearing trees in monospecific coniferous forests have the highest abundance but those in mixed-coniferous-broadleaved forests have the greatest diversity of TreMs. The occurrences of 11 out of 64 specific TreM structures were related to forest management, forest type, altitude or mean DBH. Large branch holes and buttress cavities increased with mean DBH and were found more frequently in mixed-coniferous-broadleaved forests than in the other forest types. The abundance of epiphytes on TreM bearing trees increased with altitude. This study demonstrates that the average abundance and diversity of TreMs can be predicted with readily available forest attributes. Additionally, the occurrence of specific TreMs could be described with the variation in these selected forest attributes.