Deadwood Diversity Research Articles

Optimizing enrichment of deadwood for biodiversity by varying sun exposure and tree species: An experimental approach

Abstract The enrichment of deadwood is essential for the conservation of saproxylic biodiversity in managed forests. However, existing strategies focus on a cost‐intensive increase of deadwood amount, while largely neglecting increasing deadwood diversity. Deadwood objects, that is logs and branches, from six tree species were experimentally sun exposed, canopy shaded and artificially shaded for 4 years, after which the alpha‐, beta‐ and gamma‐diversity of saproxylic beetles, wood‐inhabiting fungi and spiders were analysed. Analyses of beta‐diversity included the spatial distance between exposed deadwood objects. A random‐drawing procedure was used to identify the combination of tree species and sun exposure that yielded the highest gamma‐diversity at a minimum of exposed deadwood amount. In sun‐exposed plots, species numbers in logs were higher than in shaded plots for all taxa, while in branches we observed the opposite for saproxylic beetles. Tree species affected the species numbers only of saproxylic beetles and wood‐inhabiting fungi. The beta‐diversity of saproxylic beetles and wood‐inhabiting fungi among logs was influenced by sun exposure and tree species, but beta‐diversity of spiders by sun exposure only. For all saproxylic taxa recorded in logs, differences between communities increased with increasing spatial distance. A combination of canopy‐shaded Carpinus logs and sun‐exposed Populus logs resulted in the highest species numbers of all investigated saproxylic taxa among all possible combinations of tree species and sun‐exposure treatments. Synthesis and applications. We recommend incorporating the enrichment of different tree species and particularly the variation in sun exposure into existing strategies of deadwood enrichment. Based on the results of our study, we suggest to combine the logs of softwood broadleaf tree species (e.g. Carpinus, Populus), hardwood broadleaf tree species (e.g. Quercus) and coniferous tree species (e.g. Pinus) under different conditions of sun exposure and distribute them spatially in a landscape to maximize the beneficial effects on overall diversity.

Early-successional saproxylic beetles inhabiting a common host-tree type can be sensitive to the spatiotemporal continuity of their substrate

Intensive forest management has drastically reduced the amount and diversity of dead wood resulting in population decline of saproxylic species. Forestry practices can also disrupt spatiotemporal continuity of dead wood habitats. We studied the effects of stand- and landscape-level densities of host trees on the incidence (proportion of occupied trees) of saproxylic beetles inhabiting recently dead standing Scots pines, a common host-tree type both in natural and managed boreal forests. We compared the occurrence patterns of eight rare specialist and eight common generalist species. Saproxylic beetles were collected from a total of 315 trees in 67 forest stands, including both managed and natural forests, located in three regions which form a gradient in forest-use intensity. Species richness of the entire community at tree and stand level did not respond to the stand- and landscape-level host-tree density. The incidence of six common generalist species did not depend on the stand-level host-tree density, whereas the incidences of four rare specialist species increased with increasing host-tree density. Five out of eight rare specialist species were either significantly less common or absent from the region with the lowest landscape-level density of host trees. We conclude that rare specialist species living in recently dead pines are susceptible to changes in spatiotemporal dynamics of their host trees. To conserve rare early-successional species, it is necessary to ensure continuous input of dying trees by prolonging rotation times in mature forests, regenerating stands using seed-tree cutting and leaving as many permanent retention trees as possible.

Dead wood provides habitat for springtails across a latitudinal gradient of forests in Quebec, Canada

Understanding the importance of dead wood-associated biodiversity and related ecological functions has become increasingly important in forest ecosystem management. Yet, studies on dead wood diversity frequently focus on conspicuous organisms such as birds or saproxylic beetles, and are rarely deployed across significant climatic gradients. Here, we investigated the potential role of deadwood as a habitat for springtails, an understudied group of invertebrates generally associated with soils, and tested how these communities were influenced by climate. Black spruce logs were placed in 13 natural forest sites which were distributed among 3 latitudinal zones (southern, central and northern Quebec, Canada). We compared the springtail communities that colonized the logs through different metrics: abundance, richness and species composition. Our results indicated that dead wood was used as a habitat by 74 springtail species. A clear latitudinal diversity gradient was observed, with southern communities being on average two times richer and over 13 times more abundant than the northern ones per log. Moreover, distinct community compositions were observed in the three zones. Overall, our results suggest that (1) dead wood retention could be beneficial for small invertebrates such as springtails and (2) such biodiversity conservation measures would be more efficient if done systematically along large geographic gradients encompassing different biomes, particularly in the context of climate change.

Patterns and drivers of deadwood volume and composition in different forest types of the Austrian natural forest reserves

Deadwood is an important structural feature in forests providing essential resources for various organisms. Both forest management and conservation are increasingly focusing on the integration of deadwood into forest management. Deadwood volume and composition are driven by forest type, stand age, natural tree mortality, tree species composition and harvesting intensity. Here, we used inventory data from 28 unmanaged natural forest reserves (NFR) in Austria to analyse the patterns and drivers of: (i) the volume of standing and lying deadwood, (ii) the diversity of deadwood in different forest types. Eight forest types are located in the investigated NFRs covering a wide range of vegetation types with altitudes of 140–1825 m asl.The volumes of living wood and deadwood differed markedly between forest types. The average deadwood volume per forest type ranged from 23 m3 ha−1 in larch forests to 109 m3 ha−1 in spruce-fir-beech forests. Likewise, deadwood diversity (species diversity as well as diversity in diameter classes and degree of decomposition) differed significantly among forest types, with the highest deadwood diversity found in beech and spruce forests and the lowest in hardwood floodplain forests, carbonate pine forests and larch forests.Our results show that volume and composition of deadwood vary greatly among different forest types. Regression models revealed that the availability of deadwood was mainly driven by tree- and stand related factors (e.g. forest type, diameter at breast height and volume of living stand), whereas site-related (e.g. altitude) and climatic factors (e.g. mean annual precipitation) had a minor influence. The variables tree species diversity, aspect and slope showed no significance and were therefore not integrated into the final model.This study provides insights into deadwood availability and diversity in NFRs on a national scale, providing reference data for unmanaged temperate forests and aiding decision-making in nature conservation and forest management, since NFRs are reference areas for close-to-nature forestry.

Foraging behavior of the Eurasian Three-toed Woodpecker (Picoides tridactylus) and its implications for ecological restoration and sustainable boreal forest management

Several studies have shown that the Three-toed Woodpecker (Picoides tridactylus) is strongly favored by large-scale disturbances, including forest fires. However, natural disturbances have largely disappeared from European boreal forests because of modern forestry practices and fire suppression. We currently lack knowledge on the foraging activity and resource use of the Eurasian Three-toed Woodpecker, especially in burned forests, and this restricts our ability to develop strategies for sustainable forest management and ecological restoration aiming at improving the situation of this woodpecker and associated species. In order to fill this knowledge gap, we studied the characteristics of selected foraging substrates and the foraging behavior of the Three-toed Woodpecker during the breeding season in unburned forests and forests that have been subjected to prescribed burning. We used instantaneous sampling duringtwo consecutive springs (2016-2017), where we observed the woodpeckers’ foraging behavior during a total of 977 minutes in burned forest and 962 minutes in unburned forests. The preferred foraging substrate for Three-toed Woodpeckers in both burned and unburned forests can be characterized as freshly dead trees with a DBH > 15 cm. However, data on time spent foraging on different substrates suggest that also substrates in the 5-15 DBH range and living trees are important. Additionally, prescribed burnings led to less pronounced selection of tree species, which suggest that fire may reduce differences in abundance of saproxylic insect prey between tree species. This information on substrate selection and foraging time provide complementary knowledge and thus should be used simultaneously when management strategies for improved woodpecker habitat are developed. Our results suggest that both prescribed burning and protecting forests with high density and diversity of dead wood provides habitat opportunities for Three-toed Woodpeckers and using both in management may maximize conservation outcome

Dead wood diversity in a Norway spruce forest from the Calimani National Park (Eastern Carpathians)

The role of dead wood in forests encompasses the preservation of biodiversity, the productivity, and the storage of carbon. In this study, we aimed to investigate the variation of the dead wood volume in a subalpine Norway spruce forests. Using a regular grid, the size of the wood, ordered in a five-class scale for snags and logs and a six-class scale for stumps, was recorded. The relationship between the dead wood volume and site respectively stand characteristics by some predictive factors (stand age, altitude, human influence and site productivity) was modelled using mixed linear/nonlinear models. Dead wood volume (74.3 m3·ha-1) accounted for 18.3% of the volume (live trees and dead wood). Regarding the dead wood only, snags amounted to 44.8% of the volume and logs and stumps amounted to 46.5, and 8.7%, respectively. Snags (57.5% of the total) and logs (42.8%), were most common in the 2nd decay class, while stumps were most common in the 6th (51.2%). The distribution of the number of dead wood pieces, in terms of diameter, was obtained according to the Meyer theoretical distribution for snags and to the Gamma theoretical distribution for logs and stumps. This study completes the dead wood database from Norway spruce forests in the subalpine area to find the common features across the Carpathians Mountains. It contributes to the understanding of the dead wood dynamics in a young National Park, considering the year of establishment, consists of forests where forestry work was carried out and stands that were exempt from cutting.

Post-harvesting dynamics of the deadwood profile: the case of lowland beech-oak coppice-with-standards set-aside stands in France

In most European temperate forests, the heavy harvesting of low-quality wood for energy, a low minimum harvest diameter and a short rotation period, result in the limited deadwood resources. However, areas are being set aside in managed forests to restore deadwood levels. Coppice-with-standards is a silvicultural method characterized by periodic logging which clear-cuts coppice trees and removes some standard trees. We studied the deadwood profile (i.e., both amount and diversity) in oak-beech coppice-with-standards over time-since-the-last-harvest in order to evaluate how long it takes to recover significantly high amounts and diversity of deadwood substrates. A total of 282 circular 500-m2 plots were set up in 24 forests in southwestern France. We sampled five time-since-harvest classes within 80 years of the time elapsed since the last harvest. At the plot level, we used Generalized Linear Mixed Models to compare both deadwood volume and diversity among time classes. Diversity was also compared within time classes through accumulation curves. Deadwood legacies were very scarce after harvesting, both for volume and diversity. It took more than 70 years for deadwood amounts to become significantly higher than just after harvest; deadwood diversity was significantly higher only 30–50 years after harvesting due to quick snag recruitment. Crown deadwood, a particularly specialized resource rarely recorded, provided roughly 10–20% of the total deadwood amount throughout the study period and should be systematically recorded in further studies. Time-since-the-last-harvest was the best explanatory variable for both deadwood volume and diversity. We therefore recommend installing permanent set-aside areas to ensure deadwood conservation.

Influence of macroclimate and local conservation measures on taxonomic, functional, and phylogenetic diversities of saproxylic beetles and wood-inhabiting fungi

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.

Mitigating forest biodiversity and ecosystem service losses in the era of bio-based economy

Forests play a crucial role in the transition towards a bioeconomy by providing biomass to substitute for fossil-based materials and energy. However, a policy-policy conflict exists between the desire to increase the utilization of bio based renewable resources and the desire to protect and conserve biodiversity. Increasing forest harvest levels to meet the needs of the bioeconomy may conflict with biodiversity protection and ecosystem services provided by forests. Through an optimization framework, we examined trade-offs between increasing the extraction of timber resources, and the impacts on biodiversity and non-wood ecosystem services, and investigated possibilities to reconcile trade-off with changes in forest management in 17 landscapes in boreal forests. A diverse range of alternative forest management regimes were used. The alternatives varied from set aside to continuous cover forestry and a range of management options to reflect potential applications of the current management recommendations. These included adjustments to the number of thinning, the timing of final felling and the method of regeneration. Increasing forest harvest level to the maximum economically sustainable harvest had a negative effect on the habitat suitability index, bilberry yield, deadwood diversity and carbon storage. It resulted in a loss in variation among landscapes in their conservation capacity and the ability to provide ecosystem services. Multi-objective optimization results showed that combining different forest management regimes alleviated the negative effects of increasing harvest levels to biodiversity and non-wood ecosystem services. The results indicate that careful landscape level forest management planning is crucial to minimize the ecological costs of increasing harvest levels.

Biological traits explain bryophyte species distributions and responses to forest fragmentation and climatic variation

Abstract Forest ecosystems have been subjected to intensive exploitation, and on top of these land use‐driven habitat alterations, there is an ongoing and rapid climate change. Understanding why environmental responses differ across species and how differences are mediated by species’ traits is crucial for predicting the complex effects of global change on forest biodiversity. We used (1) single‐species distribution models and (2) multispecies predictive fourth‐corner models of varying complexity to identify critical response traits of dead wood inhabiting bryophytes and to quantify species’ relationships with climatic and forest landscape variation. We hypothesized that reproductive and life‐history traits would be mainly linked with forest connectivity, whereas morphological traits would mostly relate to (micro‐)climatic variation. The inferred trait–environment relationships based on the different fourth‐corner models were consistent. Unexpectedly, reproduction modes were more closely linked to climatic and habitat factors than to forest connectivity. Sexual reproduction was positively related to high temperatures and broadleaf trees, but negatively to high amounts of precipitation. The opposite was true for species which predominantly, or additionally, reproduce asexually. Bryophyte life‐forms were related to both habitat and climatic conditions. The positive relationship of shoot length with both high temperatures and high amounts of precipitation suggested that competitive exclusion is important in determining trailing edges of dead wood inhabiting bryophytes. Synthesis. Differences in physiological tolerances obviously play a much greater role in shaping the distributional pattern of bryophyte species with different reproductive systems than previously thought. Evidence suggests that current geographic ranges were primarily determined by physiological tolerances and competitive abilities. Species’ relationships with forest connectivity were complex and determined by the combination of reproductive traits with other critical species’ properties. Given the different species’ relationships with climatic gradients, and the varying species’ dispersal and competitive capacities, we expect clear changes in metacommunity composition following climate change and an overall decrease in the diversity of dead wood inhabiting bryophytes in Sweden.

Characteristics of boreal and hemiboreal herb-rich forests as habitats for polypore fungi

Herb-rich forests are often considered biodiversity hotspots in the boreal zone but their fungal assemblages, particularly those of wood-decaying fungi, remain poorly known. We studied herb-rich forests as habitats for polypores, a distinct group of wood-decaying fungi, and assessed the importance of tree- and stand-scale variables for polypore species richness, abundance, and diversity, including red-listed species. The data include 71 herb-rich forest stands in Finland and 4797 dead wood items, on which we made 2832 observations of 101 polypore species. Dead-wood diversity was the most important variable explaining polypore species richness and diversity, whereas increasing latitude had a negative effect. Red-listed species showed a positive response to the abundance of large-diameter dead wood, which, especially birch, supported also high general abundance of polypores. The composition of polypore assemblages reflected their host-tree species. The red-listed species did not show explicit patterns in the ordination space. Compared to old-growth spruce forests, herb-rich forests seem to host lower polypore species richness and less red-listed species. However, because of high proportion of deciduous trees in the dead wood profile, herb-rich forests have a clear complementary effect on polypore assemblages in boreal forest landscapes.

Effects of local forest continuity on the diversity of fungi on standing dead pines

Abstract Human-induced fragmentation affects forest continuity, i.e. availability of a suitable habitat for the target species over a time period. The dependence of wood-inhabiting fungi on landscape level continuity has been well demonstrated, but the importance of local continuity has remained controversial. In this study, we explored the effects of local forest continuity (microhabitat and stand level) on the diversity of wood-inhabiting fungi on standing dead trunks of Scots pine (Pinus sylvestris L.). We studied species richness and community composition of decomposers and Micarea lichens on 70 trunks in 14 forests in central Finland that differed in their state of continuity. We used dendrochronological methods to assess the detailed history of each study trunk, i.e. the microhabitat continuity. The stand continuity was estimated as dead wood diversity and past management intensity (number of stumps). We recorded 107 species (91 decomposers, 16 Micarea lichens), with a total of 510 occurrences. Using generalized linear mixed models, we found that none of the variables explained decomposer species richness, but that Micarea species richness was positively dependent on the time since tree death. Dead wood diversity was the most important variable determining the composition of decomposer communities. For Micarea lichens, the community composition was best explained by the combined effect of years from death, site and dead wood diversity. However, these effects were rather tentative. The results are in line with those of previous studies suggesting the restricted significance of local forest continuity for wood-inhabiting fungi. However, standing dead pines that have been available continuously over long periods seem to be important for species-rich communities of Micarea lichens. Rare specialists (e.g. on veteran trees) may be more sensitive to local continuity, and should be at the center of future research.

“Primeval forest relict beetles” of Central Europe: a set of 168 umbrella species for the protection of primeval forest remnants

Identification of forest stands with priority for the conservation of biodiversity is of particular importance in landscapes with a long cultural and agricultural history, such as Central Europe. A group of species with a high indicator value for the naturalness of forest ecosystems are saproxylic insects. Some of these species, especially within the order Coleoptera, have been described as primeval forests relicts. Here, we compiled a list of 168 “primeval forest relict species” of saproxylic beetles based on expert knowledge. These species can serve as focal and umbrella species for forest conservation in Central Europe. They were selected because of their dependence on the continuous presence of primeval forest habitat features, such as over-mature trees, high amounts of dead wood, and dead wood diversity, as well as their absence in managed Central European forests. These primeval forest relict species showed a moderately strong clumping pattern within the phylogeny of beetles, as indicated by phylogenetic signal testing using the D-statistic. When we controlled for phylogenetic relatedness, an ordinal linear model revealed that large body size and preference for dead wood and trees of large diameter are the main characteristics of these species. This list of species can be used to identify forest stands of conservation value throughout Central Europe, to prioritize conservation and to raise public awareness for conservation issues related to primeval forests.

Cross-taxon congruence and relationships to stand characteristics of vascular plants, bryophytes, polyporous fungi and beetles in mature managed boreal forests

Multi-taxon analyses of ecological assemblages are needed when the effects of forestry on biodiversity are examined. Management usually simplifies the structure of forests, which results in quantitative and qualitative declines in many microhabitats and species associated with them. In Fennoscandia, most forests are managed for industrial use of wood, but relatively little is known about the relationships between structural components and biodiversity in managed forests. Abundance, composition or species number of different species groups reacting similarly to variation in their environment would be a useful tool e.g. in estimating responses of species that are more difficult to sample. Thus far evidence for, or the lack of, such congruence or indicator functioning is not conclusive. We therefore examined the associations between stand structural features and species diversity and congruence between species groups of vascular plants, bryophytes and lichens, polypores and beetles. Our study was carried out in mature managed Norway spruce dominated forests in Southern Finland in 2009. Our main findings were (1) cross-taxon congruence in species richness was generally low, suggesting that any single taxonomic group performed poorly as an indicator of overall biodiversity; (2) the volume and diversity of dead trees were the most frequently detected significant predictors of species richness of the studied groups; (3) in terms of species composition, only vascular plants co-varied significantly with bryophytes and lichens; in addition, bryophytes and lichens as well as polypores co-varied significantly with stand structural features; (4) species composition of vascular plants, polypores and saproxylic beetles was associated with the volume of living trees, and in polypores it was also associated with the volumes of both dead and living deciduous trees. These results suggest that biodiversity monitoring for management and conservation requires data from several taxa. However, the volume and diversity of dead wood are useful indicators of stand-level species richness of several taxa, whereas the volume of living trees is an important indicator for the stand-level species composition of several groups. Thus, these structural variables have the potential to function as easily attainable indicators of general forest biodiversity.

Wood decay rates of 13 temperate tree species in relation to wood properties, enzyme activities and organismic diversities

Deadwood decay is an important ecosystem process in forest ecosystems, but the relative contribution of specific wood properties of tree species, activities of wood-degrading enzymes, and decomposer communities such as fungi and insects is unclear. We ask whether wood properties, in particular differences between angiosperms and gymnosperms, and organismic diversity of colonizers contribute to wood decomposition. To test this, we exposed deadwood logs of 13 tree species, covering four gymnosperms and nine angiosperm species, in 30 plots under different forest management in three regions in Germany. After a decomposition time of 6.5years Carpinus betulus and Fagus sylvatica showed the highest decay rates. We found a positive correlation of decay rate with enzyme activities, chemical wood properties (S, K concentration) and organismic diversity, while, heartwood character, lignin content, extractive concentration and phenol content were negatively correlated with decay rate across all 13 tree species. By applying a multi-model inference approach we found that the activity of the wood-degrading enzymes laccase and endocellulase, beetle diversity, heartwood presence, wood ray height and fungal diversity were the most important predictor variables for wood decay. Although we were not able to identify direct cause and effect relations by our approach, we conclude that enzyme activity and organismic diversity are the main drivers of wood decay rate, which greatly differed among tree species. Maintaining high tree species diversity will therefore result in high structural deadwood diversity in terms of decay rate and decay stage.

The importance of dead wood for hole-nesting birds: a two years study in three beech forests of central Italy

This study explored the hole-nesting bird community for two years, in three beech forest stands of central Italy. Our experimental design involved 12 replicated sampling points in each study area for a total of 36 sampling points. Stand characteristics were measured through selected environmental variables (tree diameter, tree density, volume of dead wood, diversity of dead wood and canopy closure), to develop habitat models for describing the factors affecting the abundance of hole-nesting birds. We performed generalized linear models to determine which environmental variables better explained the presence and abundance of hole-nesting birds in the three study areas. The species that showed the highest values of abundance are the Nuthatch, the Blue Tit and the Great Tit. Within the guild of hole-nesting birds there are differences in the selection of suitable trees for nesting, roosting or foraging. Primary cavity nesters (woodpeckers) are mostly related to the presence of large trees, the volume of dead...

Disentangling the effects of forest-stand type and dead-wood origin of the early successional stage on the diversity of wood-inhabiting fungi

Commercial forestry increasingly aims at both optimizing timber production and maintaining species diversity. To maintain the diversity of the species-rich group of wood-inhabiting fungi, effective forest conservation concepts that include the enrichment of dead wood in commercial forests are required. However, which type of dead wood should be enriched in which type of forest stand (coniferous or broad-leaved) is still debated. Our study aimed at (1) disentangling the relative importance of forest-stand type, dead-wood origin (tree species) and time since death and (2) determining whether fungal species richness on logs of broad-leaved trees is higher in broad-leaved stands than in coniferous stands and whether fungal species richness on logs of coniferous trees is higher in coniferous stands than in broad-leaved stands (home-field advantage). We exposed logs of 9 broad-leaved and 4 coniferous tree species in 19 broad-leaved and 9 coniferous forest stands in 2009 and surveyed the logs in 2012 and 2014 for wood-inhabiting fungi. Across all logs, fungal species richness was mainly driven by the tree species of the dead wood and time since death, whereas fungal community composition was solely driven by the tree species of the dead wood. The fungal species richness and community composition of broad-leaved logs was significantly correlated to time since death but not to forest-stand type. The fungal species richness and community composition of coniferous logs was neither affected by forest-stand type nor time since death. When individual tree species were considered, forest-stand type did not affect fungal species richness or community compositions, but fungal species richness on logs of Acer, Fagus, Carpinus and Populus increased with time since death. To increase the species richness of wood-inhabiting fungi in commercial forests, we recommend that the tree species diversity of dead wood should be increased and should especially originate from different lineages (angiosperms and gymnosperms), and that a broad variety of successional stages of dead wood should be maintained. Our results suggest that such a strategy would be effective irrespective of the tree species composition of the forest stand, as we found no support for home-field advantages in the early stage of decomposition.

Erratum: A pyrosequencing insight into sprawling bacterial diversity and community dynamics in decaying deadwood logs of Fagus sylvatica and Picea abies.

Deadwood is an important biodiversity hotspot in forest ecosystems. While saproxylic insects and wood-inhabiting fungi have been studied extensively, little is known about deadwood-inhabiting bacteria. The study we present is among the first to compare bacterial diversity and community structure of deadwood under field conditions. We therefore compared deadwood logs of two temperate forest tree species Fagussylvatica and Piceaabies using 16S rDNA pyrosequencing to identify changes in bacterial diversity and community structure at different stages of decay in forest plots under different management regimes. Alphaproteobacteria, Acidobacteria and Actinobacteria were the dominant taxonomic groups in both tree species. There were no differences in bacterial OTU richness between deadwood of Fagussylvatica and Piceaabies. Bacteria from the order Rhizobiales became more abundant during the intermediate and advanced stages of decay, accounting for up to 25% of the entire bacterial community in such logs. The most dominant OTU was taxonomically assigned to the genus Methylovirgula, which was recently described in an experiment of Fagussylvatica woodblocks. Besides tree species we were able to demonstrate that deadwood physico-chemical properties, in particular remaining mass, relative wood moisture, pH, and C/N ratio serve as drivers of community composition of deadwood-inhabiting bacteria.

Restoring volume, diversity and continuity of deadwood in boreal forests

Restoration of boreal forests by emulating natural disturbances is used to bring back typical components of natural forests that are reduced by silvicultural management. The volume, diversity and continuity of deadwood are the most important factors determining the diversity of deadwood-dependent species. In a large-scale experiment consisting of 43 experimental stands and 15 controls we assessed how alternative restoration methods enhancing deadwood availability (felling and felling + burning with two levels of felling: 20 and 40 % of initial volume of living trees, and a storm treatment) would affect short- and long-term deadwood volume and diversity using 7-year deadwood measurements and simulation modelling. In short-term, restoration by felling + burning increased both the volume and diversity of deadwood, whereas felling only increased merely the volume of deadwood. The simulations of tree growth, mortality and wood decomposition indicated that in comparison to controls, felled and storm-treated stands have greater deadwood volumes up to 40 years and felled + burned stands more than 60 years after restoration. Our results suggest that felling with 20 % of initial tree volume does not harm the future deadwood continuity, whereas intensive burning may imperil the deadwood continuity in a stand level. In conclusion, restoration clearly speeds up the development of the deadwood volumes needed to host large portions of biodiversity, and burning is the most effective restoration method in short- and long term. In practice, several restoration methods could be used concurrently in the landscape to obtain the best results.

Are biodiversity patterns of saproxylic beetles shaped by habitat limitation or dispersal limitation? A case study in unfragmented montane forests

Understanding the processes that shape biodiversity patterns is essential for ecosystem management and conservation. Local environmental conditions are often good predictors of species distribution and variations in habitat quality usually positively correlate to species richness. However, beside habitat limitation, species presence-absence may be constrained by dispersal limitation. We tested the relative importance of both limitations on saproxylic beetle diversity, using forest continuity as a surrogate for dispersal limitation and stand maturity as a surrogate for habitat limitation. Forest continuity relies on the maintenance of a forest cover over time, while stand maturity results in the presence of old-growth habitat features. Forty montane beech-fir forests in the French pre-Alps were sampled, under a balanced sampling design in which forest continuity and stand maturity were crossed. A total of 307 saproxylic beetle species were captured using flight-interception traps and Winkler–Berlese extractors. We explored the response of low- versus high-dispersal species groups to forest continuity and stand maturity. Saproxylic beetle diversity increased significantly with stand maturity and was mostly influenced by variables related to deadwood diversity at the stand scale and suitable habitat availability at the landscape scale. Surprisingly, no evidence of dispersal limitation was found, as diversity patterns were not influenced by forest continuity and associated variables, even for low-dispersal species. Our study demonstrates that in an unfragmented forest landscape, saproxylic beetles are able to colonize recent forests, as long as local deadwood resources are sufficiently diversified (e.g. tree species, position, diameter and/or decay stage).