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Historical Disturbances Determine Current Taxonomic, Functional and Phylogenetic Diversity of Saproxylic Beetle Communities in Temperate Primary Forests

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The expected future intensification of forest disturbance as a consequence of ongoing anthropogenic climate change highlights the urgent need to more robustly quantify associated biotic responses. Saproxylic beetles are a diverse group of forest invertebrates representing a major component of biodiversity that is associated with the decomposition and cycling of wood nutrients and carbon in forest ecosystems. Disturbance-induced declines or shifts in their diversity indicate the loss of key ecological and/or morphological species traits that could change ecosystem functioning. Functional and phylogenetic diversity of biological communities is commonly used to link species communities to ecosystem functions. However, our knowledge on how disturbance intensity alters functional and phylogenetic diversity of saproxylic beetles is incomplete. Here, we analyzed the main drivers of saproxylic beetle abundance and diversity using a comprehensive dataset from montane primary forests in Europe. We investigated cascading relationships between 250 years of historical disturbance mechanisms, forest structural attributes and the taxonomic, phylogenetic and functional diversity of present-day beetle communities. Our analyses revealed that historical disturbances have significant effects on current beetle communities. Contrary to our expectations, different aspects of beetle communities, that is, abundance, taxonomic, phylogenetic and functional diversity, responded to different disturbance regime components. Past disturbance frequency was the most important component influencing saproxylic beetle communities and habitat via multiple temporal and spatial pathways. The quantity of deadwood and its diameter positively influenced saproxylic beetle abundance and functional diversity, whereas phylogenetic diversity was positively influenced by canopy openness. Analyzing historical disturbances, we observed that current beetle diversity is far from static, such that the importance of various drivers might change during further successional development. Only forest landscapes that are large enough to allow for the full range of temporal and spatial patterns of disturbances and post-disturbance development will enable long-term species coexistence and their associated ecosystem functions.
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Historical Disturbances Determine
Current Taxonomic, Functional
and Phylogenetic Diversity
of Saproxylic Beetle Communities
in Temperate Primary Forests
Daniel Koza
* Marek Svitok,
Michal Wiezik,
Martin Mikola
Simon Thorn,
Arne Buechling,
´k Hofmeister,
Radim Matula,
Volodymyr Trotsiuk,
Radek Bac
ˇimir Begovic
ˇch C
Martin Dus
Michal Frankovic
Jakub Hora
Pavel Janda,
Ondrej Kameniar,
Thomas A. Nagel,
Joseph L. Pettit,
Jessika M. Pettit,
Michal Synek,
Adela Wiezikova
and Miroslav Svoboda
Department of Forest Ecology, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences Prague, Kamy
´cka 129, 165
21 Prague, Czech Republic;
Faculty of Ecology and Environmental Sciences, Technical University in Zvolen, T.G. Masaryka 24, 960
01 Zvolen, Slovakia;
Department of Ecosystem Biology, Faculty of Science, University of South Bohemia, Branis
´1760, 370 05
Ceske Budejovice, Czech Republic;
Field Station Fabrikschelichach, Biocenter, University of Wu¨ rzburg, Glashu¨ ttenstraße 5, 96181
Rauhenebrach, Germany;
Swiss Federal Institute for Forest, Snow and Landscape Research WSL, Zu¨ rcherstrasse 111, 8903 Bir-
mensdorf, Switzerland;
Department of Forest Protection and Entomology, Faculty of Forestry and Wood Sciences, Czech University
of Life Sciences Prague, Kamy
´cka 129, 165 21 Prague, Czech Republic;
Department of Forestry and Renewable Forest Resources,
Biotechnical Faculty, University of Ljubljana, 1000 Ljubljana, Slovenia
The expected future intensification of forest dis-
turbance as a consequence of ongoing anthro-
pogenic climate change highlights the urgent need
to more robustly quantify associated biotic re-
sponses. Saproxylic beetles are a diverse group of
forest invertebrates representing a major compo-
nent of biodiversity that is associated with the
decomposition and cycling of wood nutrients and
carbon in forest ecosystems. Disturbance-induced
declines or shifts in their diversity indicate the loss
of key ecological and/or morphological species
traits that could change ecosystem functioning.
Functional and phylogenetic diversity of biological
communities is commonly used to link species
communities to ecosystem functions. However, our
knowledge on how disturbance intensity alters
functional and phylogenetic diversity of saproxylic
beetles is incomplete. Here, we analyzed the main
drivers of saproxylic beetle abundance and diver-
sity using a comprehensive dataset from montane
primary forests in Europe. We investigated cas-
cading relationships between 250 years of historical
Received 12 November 2019; accepted 22 March 2020;
published online 20 April 2020
Electronic supplementary material: The online version of this article
( contains supplementary
material, which is available to authorized users.
Authors Contributions: DK, MM, MW, ST, MSvi, MSvo, JHor con-
ceived the ideas and designed study. DK, MW, MM, PJ, RB, VC
ˇ, VT, OK,
AW, MSy, MD and MF contributed to and organized data collection.
MSvi, ST, DK analyzed the data. DK, ST, AB, MM, TAN, JLP, JMP, JHof,
RM led the writing of the manuscript. All authors contributed critically to
the study and gave final approval for publication.
*Corresponding author; e-mail:
Ecosystems (2021) 24: 37–55
2020 Springer Science+Business Media, LLC, part of Springer Nature
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... Disturbances predominantly affect forest ecosystems by creating patches of dead trees varying in spatial extent and severity (Pickett and White 1985;Čada et al. 2020). In contrast with managed forests, dead trees and their components remain in unmanaged forest as disturbance legacies (Seidl et al. 2014), contribute to the total carbon pool (Commarmot et al. 2005;Glatthorn et al. 2018), help facilitate regeneration after disturbance (Zielonka 2006;Michalová et al. 2017), whilst also providing important structural elements for biodiversity (Stokland et al. 2012;Thorn et al. 2017;Kozák et al. 2020). ...
... However, there is emerging evidence that medium-to high-severity and scale disturbances were also historically a part of BDPF disturbance regimes, although to a much lower extent than in SDPF (Frankovič et al. 2021). The diversity of disturbance regimes has differing effects on forest structure, which thereby has divergent effects on habitat availability for different taxonomic groups of species, thereby altering biological assemblages (Kozák et al. 2020;Langbehn et al. 2021;Ferenčík et al. 2022). Therefore, disentangling the impacts of disturbances across different forest types is crucial in these times of rapid biodiversity decline. ...
... European hornbeam (Carpinus betulus L.), Scots pine (Pinus sylvestris L.) and other species. Annual mean temperatures range from 1.6 to 3.4 °C in SDPF stands and from 5 to 5.5 in BDPF stands, annual precipitation varies from 1,205 to 1,365 mm in SDPF (Kozák et al. 2020) and around 1,067 mm in BDPF stands (Harris et al. 2020). ...
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Mountain spruce- and beech-dominated forests (SDPF and BDPF) are of major importance in temperate Europe. However, information on the differences between their historical disturbance regimes, structures, and biodiversity is still incomplete. To address this knowledge gap, we established 118 circular research plots across 18 primary forest stands. We analysed the disturbance history of the last 250 years by dendrochronological methods and calculated disturbance frequency, severity, and timing. We also measured forest structure (DBH, tree density, volume of deadwood, and other parameters). Breeding bird populations were examined by point count method during the spring seasons 2017–2018 (SDPF) and 2019–2020 (BDPF). Using direct ordination analysis, we compared the disturbance history, structure and bird assemblage in both forest types. While no differences were found regarding disturbance regimes between forest types, forest structure and bird assemblages were significantly different. SDPF had a significantly higher density of cavities and higher canopy openness, while higher tree species richness and more intense regeneration was found in BDPF. Bird assemblage showed higher species richness in BDPF, but lower total abundance. Most bird species which occurred in both forest types were more numerous in spruce-dominated forests, but more species occurred exclusively in BDPF. Further, some SDPF- preferring species were found in naturally disturbed patches in BDPF. We conclude that although natural disturbances are important drivers of primary forest structures, differences in the bird assemblages in the explored primary forest types were largely independent of disturbance regimes.
... A high internal diversity for these ecosystems has also been demonstrated in northern Fennoscandia and Russia, where tree species composition, disturbance regime, and abiotic composition can greatly vary among landscapes (Shorohova et al., 2009(Shorohova et al., , 2011. Primary forests dominated by Norway spruce in the alpine regions of eastern Europe (Kozák et al., 2021;Meigs et al., 2017;Trotsiuk et al., 2014) also provide examples of old-growth dynamics, where such reference forests are now almost entirely absent. Boreal old-growth forests are therefore dynamic and diverse ecosystems, from the circumboreal to the local scale. ...
... Deadwood-related species often depend on specific substrate characteristics, e.g., tree species, decay stage, contact with the ground, cause of death, and size (Janssen et al., 2011;McMullin et al., 2010;Stokland et al., 2012), and the high abundance and diversity of deadwood at the stand scale often results in greater deadwood-related species richness (Lassauce et al., 2011;Wagner et al., 2014). Kozák et al. (2021), for example, underscored that the characteristics of the secondary disturbance regime, e.g., severity, frequency, and time since the last disturbance, strongly influence saproxylic beetle diversity in alpine forests dominated by Norway spruce. Similarly, trees that survived a disturbance can also act as refugia for lowdispersal species, such as lichens, facilitating their recolonization of a disturbed area (Zemanová et al., 2017). ...
... Many abiotic, historical, and spatial factors can hence influence the characteristics of old-forest habitats and their attractiveness to boreal species. The complexity of the interactions between these factors can make it difficult to identify clear links between the structural/functional biodiversity and specific structural/ecological attributes Kozák et al., 2021;Larrieu et al., 2018). Experiments in close-to-nature silvicultural practices can be effective in gaining a direct understanding of how disturbance dynamics can influence biodiversity (Fenton et al., 2013;Franklin et al., 2019;Koivula and Vanha-Majamaa 2020). ...
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Boreal old-growth forests are specific and often undervalued ecosystems, as they present few of the structural attributes that usually define old forests in the collective culture. Yet, these ecosystems are characterized by exceptional naturalness, integrity, complexity, resilience, as well as structural and functional diversity. They therefore serve as biodiversity hot spots and provide crucial ecosystem services. However, these forests are under significant threat from human activities, causing a rapid and large-scale reduction in their surface area and integrity. The multiple values associated with boreal old-growth forests should be therefore better acknowledged and understood to ensure the sustainable management of boreal landscapes.
... Tree hollows can be surveyed with emergence traps, a standardized absolute method that allows quantitative abundance monitoring over time (i.e., complete years) [45], and it avoids one of the commonest shortcomings that occurs when evaluating long-term insect population variations [46]. Finally, this community is very sensitive to some of the main global stressors, namely land use changes, increasing temperatures, or climate-induced changes in natural disturbance regimes [8,[47][48][49]. ...
... We hypothesized that tree hollow-saproxylic insect networks in Mediterranean woodland types would be nested as reported in [54], and this specialized interaction pattern would tend to remain constant in spite of the high temporal turnover in species composition and interactions [29,31,32,55]. Nonetheless, major changes in the interaction properties of tree hollow-saproxylic networks are expected due to foreseeable temporal shifts in species diversity and species interactions reported in natural ecosystems in general-e.g., [56]-and in saproxylic communities in forest ecosystems in particular [2,49]. Losses in species richness and abundance, and the inherent in-depth restructuring of interactions that they entail, are expected to provoke bottom-up cascading effects on the tree hollow-saproxylic food web that will lead to increased vulnerability, e.g., [13,15,57]. ...
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Simple Summary Insect populations are facing unprecedented changes in many ecosystems worldwide. However, do these changes make insect communities more vulnerable? The study of interaction networks can help to answer this question. We assessed the adequacy of network tools to address the long-term variation (after 11 years) of diversity patterns of the saproxylic (wood-dependent) beetle communities that inhabit tree hollows in three representative Mediterranean woodland types. To explore saproxylic communities’ vulnerability to microhabitat loss, we simulated hollow extinctions and recreated feasible future threat scenarios based on decreasing microhabitat suitability. Contrasting responses in diversity patterns among woodland types were found, whereas interaction patterns generally showed substantial temporal variations in the way that saproxylic beetles interact with tree hollows (less interconnected and specialized networks). Network procedures evidenced increased saproxylic communities’ vulnerability, and this situation could worsen in potential future scenarios with decreased microhabitat suitability. The valuable information that ecological networks provide should be considered for improving management and conservation programs. Abstract Insect communities are facing contrasting responses due to global change. However, knowledge on impacts of communities’ reorganizations is scarce. Network approaches could help to envision community changes in different environmental scenarios. Saproxylic beetles were selected to examine long-term variations in insect interaction/diversity patterns and their vulnerability to global change. We evaluated interannual differences in network patterns in the tree hollow–saproxylic beetle interaction using absolute samplings over an 11-year interval in three Mediterranean woodland types. We explored saproxylic communities’ vulnerability to microhabitat loss via simulated extinctions and by recreating threat scenarios based on decreasing microhabitat suitability. Although temporal diversity patterns varied between woodland types, network descriptors showed an interaction decline. The temporal beta-diversity of interactions depended more on interaction than on species turnover. Interaction and diversity temporal shifts promoted less specialized and more vulnerable networks, which is particularly worrisome in the riparian woodland. Network procedures evidenced that saproxylic communities are more vulnerable today than 11 years ago irrespective of whether species richness increased or decreased, and the situation could worsen in the future depending on tree hollow suitability. Network approaches were useful for predicting saproxylic communities’ vulnerability across temporal scenarios and, thus, for providing valuable information for management and conservation programs.
... Compared to managed forests, unmanaged forest ecosystems are generally considered beneficial for biodiversity (Paillet et al., 2010;Bruun and Heilmann-Clausen, 2021). Since unmanaged forests are prone to small and large natural disturbances-allowing latesuccessional phases to develop-they tend to have superior structural complexity than managed stands, favouring specific species assemblages (Kozák et al., 2021;McCarthy and Burgman, 1995). Indeed, natural disturbances occurring over a range of spatial and temporal scales likely provide more favourable conditions for different components of biodiversity due to, for example, a greater volume of deadwood (Lassauce et al., 2011;Paillet et al., 2015), presence of very large trees (Paillet et al., 2015;Ali and Wang, 2021), and greater microhabitat presence and diversity (Paillet et al., 2017;Winter and Möller, 2008). ...
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Growing evidence suggests that forest management practices are threatening the long-term conservation of a number of animal, fungi, and plant species worldwide. Although unmanaged forests are considered important for biodiversity, forest management continues to affect these vital habitats. We systematically reviewed the scientific literature to gain insight into the effects of forest management abandonment on biodiversity. We calculated log response ratio effect sizes to perform a meta-analysis on species richness between still managed (MAN) and no longer managed (NLM) forests, throughout the world's boreal and temperate forest ecosystems. Our statistical approach included improvements relative to a rigorous treatment of pseudo-replication, an objective choice of taxonomic resolution, and new forms of residual heterogeneity. In our simplest model, plant species richness was significantly lower in NLM than in MAN stands (−14.7 %), while fungi (+10.2 %) and animal (+10.6 %) richness were higher in NLM sites but not significantly (at the 5 % level). Models were improved by adding precipitation, time since abandonment of management (TSA), and their interaction. Effect size estimate for total species richness in NLM forests significantly increased with TSA in wetter climates (+14.3 %), but decreased with TSA in drier climates; fungi richness (+18.1 %) became significantly higher in NLM. These results underline the taxa-dependent responses to management abandonment as well as the slow but real context-dependant recovery capacity of biodiversity after management abandonment. Our findings support the call for further coordinated research to confirm identified patterns, then context-relevant policies aiming to set aside forest zones in production forest systems for conservation purposes
... To preserve natural montane spruce-forest communities in their full complexity, nature protection should be focused on large forest areas that encompasses all disturbance regimes (Kozák et al. 2021). Such "disturbance diversity" is essential for sustainable forest development, including its overall plant diversity, and it plays an important role in forest adaptation to climate change. ...
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Forest decline caused by climate change has been a growing challenge for European foresters for decades. The accumulation of tree-related microhabitats (TreMs) and deadwood during decline can enhance stand structural heterogeneity and provide crucial habitat features for many forest ecological guilds. We analysed changes in deadwood and TreM assemblages using a trait-based approach in three case studies: drought-induced decline in highland Pyrenean fir and lowland oak forests, and windstorm/pest-induced dieback in highland Bavarian spruce forests. Decline caused significant changes in deadwood and TreM characteristics and composition in three forest contexts. However, tree density with cavities, exudates, or crown deadwood was not linked to decline intensity. Declining conifer forests had more large deadwood and downed woody debris, and their TreM assemblages were more saproxylic, less epixylic, and included more cracks and exposed sapwood. TreM assemblages in drought-declining forests had higher diversity, functional richness, and more dead tops than healthy stands. In Bavarian spruce forests, there was more decayed downed deadwood, and the TreM assemblages were more associated with the base of the tree, snags, and logs. Overall, forest decline significantly boosts ecological niche resources, typically scarce in managed forests, which could benefit many forest biodiversity groups. Though post-disturbance management should respect tree species-dependent economic balance and avoid phytosanitary risks, it should also consider the ecological benefits of decline-induced heterogeneity. Graphical Abstract
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The European biodiversity and forest strategies rely on forest sustainable management (SFM) to conserve forest biodiversity. However, current sustainability assessments hardly account for direct biodiversity indicators. We focused on forest multi-taxon biodiversity to: i) gather and map the existing information; ii) identify knowledge and research gaps; iii) discuss its research potential. We established a research network to fit data on species, standing trees, lying deadwood and sampling unit description from 34 local datasets across 3591 sampling units. A total of 8724 species were represented, with the share of common and rare species varying across taxonomic classes: some included many species with several rare ones (e.g., Insecta); others (e.g., Bryopsida) were represented by few common species. Tree-related structural attributes were sampled in a subset of sampling units (2889; 2356; 2309 and 1388 respectively for diameter, height, deadwood and microhabitats). Overall, multi-taxon studies are biased towards mature forests and may underrepresent the species related to other developmental phases. European forest compositional categories were all represented, but beech forests were over-represented as compared to thermophilous and boreal forests. Most sampling units (94%) were referred to a habitat type of conservation concern. Existing information may support European conservation and SFM strategies in: (i) methodological harmonization and coordinated monitoring; (ii) definition and testing of SFM indicators and thresholds; (iii) data-driven assessment of the effects of environmental and management drivers on multi-taxon forest biological and functional diversity, (iv) multi-scale forest monitoring integrating in-situ and remotely sensed information.
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Purpose of Review The increasing impact of droughts, wildfires and windstorms in temperate areas poses a significant challenge to the adaptation capacity of forests and their associated arthropod communities. Organisms, organic material, and environmental conditions occurring after disturbances, i.e. the disturbance legacies, shape arthropod communities during their transition from pre- to post-disturbance conditions. We describe the contribution of disturbance legacies to the organization of forest arthropod communities following droughts, wildfires, or windstorms. We also highlight how forest conditions, arthropod traits and post-disturbance management influence disturbance legacies and their impact on arthropod communities. Recent Findings Key disturbance legacies include surviving arthropods, micro-environmental legacies, and tree- and ground-related resources. Most of these are driven by canopy openness and tree condition. For arthropods, dispersal ability and other biological and demographic traits determine their vulnerability to disturbances, but also their capacity to colonize post-disturbance microhabitats, and withstand micro-environmental legacies. Dominant tree species and management strategies influence disturbance regimes and mediate the pattern of their legacies. Droughts, wildfires and windstorms have idiosyncratic effects on disturbance legacies, and arthropod taxa can have specific responses to legacies, making it difficult to predict the likely composition of post-disturbance arthropod communities. Summary This review highlights a particular gap in our understanding of the effects of drought on forest arthropod communities and the need for more research in this area. In addition, a better understanding of how forest arthropod communities are altered by changes in disturbance regimes is urgently needed. Our goal is to foster an improved understanding of the role of disturbance legacies for forest arthropod communities in order to improve management decisions and promote the conservation of forest arthropod species.
Understanding temporal and spatial variations in historical disturbance regimes across intact, continuous, and altitudinally diverse primary forest landscapes is imperative to help forecast forest development and adapt forest management in an era of rapid environmental change. Because few complex primary forest landscapes remain in Europe, previous research has largely described disturbance regimes for individual forest types and smaller isolated stands. We studied the largest but still largely unprotected mountain primary forest landscape in temperate Europe, the Fagaraș Mountains of Romania. To describe historical disturbance regimes and synchronicity in disturbance activity and trends between two widespread forest community types, dominated by Norway spruce (Picea abies (L.) Karst.) and European beech (Fagus sylvatica L.), we established 191 permanent study plots (70 beech; 121 spruce) across 11 valleys, thereby providing information at both stand and landscape levels. We used a dendrochronological approach to reconstruct and describe the spatiotemporal patterns of historical disturbances. We observed a diverse spectrum of disturbance severities and timing across the forest landscape. High-severity disturbances created periods of synchrony in disturbance activity at the landscape scale, while moderate- and low-severity disturbances were asynchronous and random in both spruce- and beech-dominated primary forests. We detected a peak of canopy disturbance across the region at the end of the nineteenth century, with the most important periods of disturbance between the 1890s and 1910s. At the stand scale, we observed periods of synchronised disturbances with varying severities across both forest types. The level of disturbance synchrony varied widely among the stands. The beta regression showed that spruce forests had significantly higher average synchrony and higher between-stand variability of synchrony than the beech-dominated forests. Synchronised disturbances with higher severity were infrequent, but they were critical as drivers of subsequent forest development pathways and dynamics across both forest types. Our results provide valuable insight into future resilience to climate-driven alterations of disturbance regimes in spruce- and beech-dominated mountain temperate forests in the Carpathians. We suggest that conservation efforts should recognize strictly protecting large continuous and altitudinally diversified forest landscapes such as Fagaraș Mts. as a necessary measure to tackle climate change and ensure temporal and spatial structural heterogeneity driven by a wide range of disturbances. The diverse and synchronous disturbance activity among two interconnected forest vegetation types highlights the need for complex spatiotemporal forest management approaches that emulate disturbance synchronicity to foster biodiversity across multiple forest vegetation types within forest landscapes.
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Natural disturbances are an integral part of forest ecosystems. They ensure the creation of new habitats, maintain high spatial heterogeneity and disrupt the ecological succession processes. Forest ecosystems in a particular region are historically adapted to the disturbance complexes affecting that region (i.e. the disturbance regime). They are also largely affected by so-called anthropogenic disturbances (e.g. logging). The process of progressive tree death due to these different disturbances is called "forest dieback". Generally, these diebacks are followed by salvage or sanitation logging to harvest the commercial value of the trees before they deteriorate or to contain future pest outbreaks. This logging is considered to be additional disturbance. However, ongoing changes in climate and land use are leading to changes in the regime of these disturbances. In the extreme, if the change in these regimes is too great, it can lead to a shift towards a non-forest ecosystem. These regime shifts could then result in regional extinctions of forest species and alter the ecosystem services provided by forests to human societies. The study of these forest diebacks is therefore of central importance. In this thesis, we focus on the response of saproxylic beetles (i.e. beetles linked for part or all of their life cycle to dead wood), an ecological group threatened in temperate managed forests due to the scarcity of the dead wood resource. We also analyse habitat changes caused by these diebacks (i.e. disturbance legacies). For this purpose, we study three case studies of European dieback: (i) Pyrenean fir (Abies alba) and (ii) Loire Valley oak (Quercus spp.) caused by droughts, and (iii) Bavarian spruce (Picea abies) caused by storms and Ips typographus} outbreaks. On each of these sites, we inventoried the dead wood and tree-related microhabitats present on the plots as well as saproxylic beetles. These surveys revealed significant changes in habitats, resulting in increases in dead wood and changes in tree-related microhabitat composition. These changes appeared to be modulated by the severity of dieback. In cascade, these habitat changes induced modifications in the local composition of saproxylic beetles. For both coniferous forests, habitat changes induced positive effects of dieback on local beetle diversity, both taxonomic and functional. Furthermore, we observed homogenisations of saproxylic beetle communities in the landscape due to dieback. Furthermore, we highlighted the importance of dieback at the landscape scale on local taxonomic, functional and phylogenetic assemblages of saproxylic beetles. We also show that functional and phylogenetic diversity were mostly driven by landscape processes. Finally, we noted that sanitary and salvage logging did not affect local beetle diversity but strongly altered their ecological relationships. Our results highlight the value that can be gained from declining areas for the conservation of otherwise threatened species groups in managed forest areas, by maintaining the habitats created (i.e. dead wood and tree-related microhabitats). Finally, they highlight the need to consider the maintenance of these declining areas on a landscape scale.
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Deadwood and microhabitats play a fundamental role in many forest ecosystem processes. Deadwood provides the substrate for a multitude of wood-dependent organisms, as well as a variety of microhabitats. Deadwood is a key factor in maintaining the ecosystem functionality and increasing the overall forest biodiversity. In Mediterranean forests, the relationship between stand-structure attributes and species-diversity indicators is still poorly investigated. In this study, we hypothesized that the abundance of saproxylic species was influenced by (i) the composition and amount of deadwood, and (ii) the heterogeneity in types and density of microhabitats. The investigation was carried out in a broadleaved mixed forest located in Central Apennine (Italy), in which silvicultural interventions were interrupted for several decades. The experimental area extends on approximately 240 ha; structural traits, deadwood and microhabitats were sampled on 50 plots of 530 m 2. Saproxylic beetles were collected using window flight traps and emergence traps on decaying deadwood. We applied joint species distribution models (JSDM) to quantify the relationship between forest attributes and the abundance of sa-proxylic species, explicitly including their functional traits (e.g., trophic level). Results demonstrated that mi-crohabitats, living biomass, basal area and coarse woody debris had a significant effect of saproxylic beetles belonging to different trophic categories. Considering the conservation status, only the stand basal area significantly affected the abundance of Near Threatened (NT) saproxylic beetles. This study highlighted the importance of integrating multiple biodiversity indicators to find sustainable solutions for conservation purposes, unlike many studies on conservation-oriented management strategies, more frequently focused on independent forest biodiversity indicators.
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The successional dynamics of forests—from canopy openings to regeneration, maturation, and decay—influence the amount and heterogeneity of resources available for forest‐dwelling organisms. Conservation has largely focused only on selected stages of forest succession (e.g., late‐seral stages). However, to develop comprehensive conservation strategies and to understand the impact of forest management on biodiversity, a quantitative understanding of how different trophic groups vary over the course of succession is needed. We classified mixed mountain forests in Central Europe into nine successional stages using airborne Li DAR . We analysed α‐ and β‐diversity of six trophic groups encompassing approximately 3,000 species from three kingdoms. We quantified the effect of successional stage on the number of species with and without controlling for species abundances and tested whether the data fit the more‐individuals hypothesis or the habitat heterogeneity hypothesis. Furthermore, we analysed the similarity of assemblages along successional development. The abundance of producers, first‐order consumers, and saprotrophic species showed a U‐shaped response to forest succession. The number of species of producer and consumer groups generally followed this U‐shaped pattern. In contrast to our expectation, the number of saprotrophic species did not change along succession. When we controlled for the effect of abundance, the number of producer and saproxylic beetle species increased linearly with forest succession, whereas the U‐shaped response of the number of consumer species persisted. The analysis of assemblages indicated a large contribution of succession‐mediated β‐diversity to regional γ‐diversity. Synthesis and applications . Depending on the species group, our data supported both the more‐individuals hypothesis and the habitat heterogeneity hypothesis. Our results highlight the strong influence of forest succession on biodiversity and underline the importance of controlling for successional dynamics when assessing biodiversity change in response to external drivers such as climate change. The successional stages with highest diversity (early and late successional stages) are currently strongly underrepresented in the forests of Central Europe. We thus recommend that conservation strategies aim at a more balanced representation of all successional stages.
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Wood-inhabiting fungi and saproxylic beetles are threatened by habitat degradation. Our understanding of the importance of macroclimate and local factors determining their taxonomic diversity has increased, but determinants of functional and phylogenetic diversity are poorly understood. We investigated assemblages of wood-inhabiting fungi and saproxylic beetles along a 1000 m elevational gradient of a temperate low mountain range. We (i) tested the relative importance of macroclimate (i.e. elevation) and local variables (microclimate, i.e. canopy closure, amount and diversity of dead wood) in determining observed and rarefied diversities and (ii) explored whether determinants of observed functional and phylogenetic diversities match those of taxonomic diversity. For both taxa, the determinants of observed phylogenetic and functional diversities largely matched those of taxonomic diversity. The diversity of wood-inhabiting fungi was predominantly determined by local variables, whereas that of saproxylic beetles was determined by both local variables and elevation. Taxonomic and phylogenetic diversities of saproxylic beetles decreased with increasing elevation, but standardized functional richness and entropy of both groups increased with increasing elevation. Diversities of wood-inhabiting fungi increased with canopy closure, while diversities of saproxylic beetles decreased with increasing canopy closure. Microclimate and dead-wood amount and diversity affected the observed and rarefied diversity of both saproxylic taxa, which justifies conservation actions that focus on attributes of dead wood and canopy cover. The contrasting responses of fungi and beetles highlight the need for amounts of diverse dead wood in the various microclimates to preserve functional and phylogenetic diversities of saproxylic organisms.
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Aim Primary forests have high conservation value but are rare in Europe due to historic land use. Yet many primary forest patches remain unmapped, and it is unclear to what extent they are effectively protected. Our aim was to (1) compile the most comprehensive European‐scale map of currently known primary forests, (2) analyse the spatial determinants characterizing their location and (3) locate areas where so far unmapped primary forests likely occur. Location Europe. Methods We aggregated data from a literature review, online questionnaires and 32 datasets of primary forests. We used boosted regression trees to explore which biophysical, socio‐economic and forest‐related variables explain the current distribution of primary forests. Finally, we predicted and mapped the relative likelihood of primary forest occurrence at a 1‐km resolution across Europe. Results Data on primary forests were frequently incomplete or inconsistent among countries. Known primary forests covered 1.4 Mha in 32 countries (0.7% of Europe’s forest area). Most of these forests were protected (89%), but only 46% of them strictly. Primary forests mostly occurred in mountain and boreal areas and were unevenly distributed across countries, biogeographical regions and forest types. Unmapped primary forests likely occur in the least accessible and populated areas, where forests cover a greater share of land, but wood demand historically has been low. Main conclusions Despite their outstanding conservation value, primary forests are rare and their current distribution is the result of centuries of land use and forest management. The conservation outlook for primary forests is uncertain as many are not strictly protected and most are small and fragmented, making them prone to extinction debt and human disturbance. Predicting where unmapped primary forests likely occur could guide conservation efforts, especially in Eastern Europe where large areas of primary forest still exist but are being lost at an alarming pace.
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As the terrestrial human footprint continues to expand, the amount of native forest that is free from significant damaging human activities is in precipitous decline. There is emerging evidence that the remaining intact forest supports an exceptional confluence of globally significant environmental values relative to degraded forests, including imperilled biodiversity, carbon sequestration and storage, water provision, indigenous culture and the maintenance of human health. Here we argue that maintaining and, where possible, restoring the integrity of dwindling intact forests is an urgent priority for current global efforts to halt the ongoing biodiversity crisis, slow rapid climate change and achieve sustainability goals. Retaining the integrity of intact forest ecosystems should be a central component of proactive global and national environmental strategies, alongside current efforts aimed at halting deforestation and promoting reforestation.
Given the global intensification of forest management and climate change, protecting and studying forests that develop free of direct human intervention-also known as primary forests-are becoming increasingly important. Yet, most countries still lack data regarding primary forest distribution. Previous studies have tested remote sensing approaches as a promising tool for identifying primary forests. However, their precision is highly dependent on data quality and resolution, which vary considerably. This has led to underestimation of primary forest abundance and distribution in some regions, such as the temperate zone of Europe. Field-based inventories of primary forests and methodologies to conduct these assessments are inconsistent; incomplete or inaccurate mapping increases the vulnerability of primary forest systems to continued loss from clearing and land-use change. We developed a comprehensive methodological approach for identifying primary forests, and tested it within one of Europe's hotspots of primary forest abundance: the Carpathian Mountains. From 2009 to 2015, we conducted the first national-scale primary forest census covering the entire 49,036 km 2 area of the Slovak Republic. We analyzed primary forest distribution patterns and the representativeness of potential vegetation types within primary forest remnants. We further evaluated the conservation status and extent of primary forest loss. Remaining primary forests are small, fragmented, and often do not represent the potential natural vegetation. We identified 261 primary forest localities. However, they represent only 0.47% of the total forested area, which is 0.21% of the country's land area. The spatial pattern of primary forests was clustered. Primary forests have tended to escape anthropogenic disturbance on sites with higher elevations, steeper slopes, rugged terrain, and greater distances from roads and settlements. Primary forest stands of montane mixed and subalpine spruce forests are more abundant compared to broadleaved forests. Notably, several habitat types are completely missing within primary forests (e.g., floodplain forests). More than 30% of the remaining primary forests are not strictly protected, and harvesting occurred at 32 primary forest localities within the study period. Almost all logging of primary forests was conducted inside of protected areas, underscoring the critical status of primary forest distribution in this part of Europe. Effective conservation strategies are urgently needed to stop the rapid loss and fragmentation of the remaining primary forests. Our approach based on precise, field-based surveys is widely applicable and transferrable to other fragmented forest landscapes.
Tree-related microhabitats (TreMs) are important features for the conservation of biodiversity in forest ecosystems. Although other structural indicators of forest biodiversity have been extensively studied in recent decades, TreMs have often been overlooked, either due to the absence of a consensual definition or a lack of knowledge. Despite the increased number of TreM studies in the last decade, the role of drivers of TreM profile in primary forests and across different geographical regions is still unknown. To evaluate the main drivers of TreM density and diversity, we conducted the first large-scale study of TreMs across European primary forests. We established 146 plots in eight primary forests dominated by European beech (Fagus sylvatica L.) in the Carpathian and Dinaric mountain ranges. Generalized linear mixed effect models were used to test the effect of local plot characteristics and spatial variability on the density and diversity (alpha, beta, and gamma) of TreMs. Total TreM density and diversity were significantly positively related with tree species richness and the proportion of snags. Root mean square tree diameters were significantly related to alpha and gamma diversity of TreMs. Both regions reached similarly high values of total TreM densities and total TreM densities and diversity were not significantly different between the two regions; however, we observed between the two regions significant differences in the densities of two TreM groups, conks of fungi and epiphytes. The density and diversity of TreMs were very high in beech-dominated mountain primary forests, but their occurrence and diversity was highly variable within the landscapes over relatively short spatial gradients (plot and stand levels). Understanding these profile provides a benchmark for further comparisons, such as with young forest reserves, or for improving forest management practices that promote biodiversity.
Primary forests represent the ultimate intact habitat for saproxylic insects. However, their extent has been considerably reduced over the past centuries, and those remaining are very heterogeneously distributed. Primary forests are still locally abundant in tropical and boreal zones but are rare in temperate zones. Consequently, many saproxylic insects that were adapted to typical characteristics of primary forests, such as large amounts of dead wood or overmature and senescent trees, might have become extinct regionally due to habitat loss. The remaining primary forests therefore function as refuges for those saproxylic species that cannot survive in managed forests because of their high ecological requirements. Here we identify six characteristics of primary forests important for saproxylic insects that differentiate these forests greatly from managed forests, namely, absence of habitat fragmentation, continuity, natural disturbance regimes, dead-wood amount and quality, tree species composition and habitat trees. These six characteristics highlight the importance of primary forests for the conservation of saproxylic insects in all three main climatic domains (tropical, boreal and temperate). As primary forests are rare in northern temperate zones and are being dramatically lost in boreal and tropical zones, we propose that they should be strictly conserved independently of their climatic zone. Furthermore, we recommend that studies in primary forests intensify to provide reference data for integrating primary forest characteristics into managed forests to improve the conservation of saproxylic species.
Natural amounts of dead wood in a forest vary considerably, depending on living tree biomass, decomposition rates, and rates of dead-wood development. In natural forests, dead wood is created by the senescence of trees and natural disturbances. However, dead-wood amounts in many forest ecosystems worldwide nowadays are largely influenced by human activities, such as timber and fuel wood production and post-disturbance salvage logging. The biodiversity of saproxylic insects is usually positively correlated with the amount of dead wood, and dead-wood amount affects species composition and functional characteristics of saproxylic assemblages. Dead-wood amount is in turn correlated with dead-wood diversity, and several studies highlight the importance of dead-wood diversity for saproxylic biodiversity, which suggests that habitat heterogeneity is a major driver behind the positive relationship between dead-wood amount and biodiversity. The strength of this relationship is mediated by temperature. Effects of both temporal forest continuity and spatial connectivity are often linked to differences in dead-wood amount. Frequent interactions and correlations between dead-wood amount and other habitat factors indicate that future studies should aim more precisely at unraveling the importance of individual factors for saproxylic biodiversity, which will help to improve conservation strategies to counteract negative effects of anthropogenically altered dead-wood amount and diversity. Such conservation strategies, particularly in Europe and North America, include passive and active measures to retain dead wood in managed forests and to restore amounts and diversity of dead wood similar to levels in natural forests. More research is needed in the subtropics and tropics where conservation strategies rarely consider dead wood, although the few existing studies suggest that dead wood is an important factor for biodiversity in these regions.