Deadwood Structures Research Articles

Fungi and deadwood diversity: A test of the area‐heterogeneity trade‐off hypothesis

Abstract Environmental heterogeneity is one of the most fundamental drivers of species diversity. For decades, ecologists have suggested that heterogeneity–diversity relationships are generally positive. But today, a greater variety of heterogeneity–diversity relationships is discussed. In this study, we contrasted two hypotheses for wood‐inhabiting fungi: The classical heterogeneity–diversity hypothesis, which predicts positive relationships due to an increase in niche dimensionality with increasing heterogeneity. And the more recently stated area‐heterogeneity trade‐off hypothesis, that predicts a unimodal pattern due to an inherent trade‐off between the number of occupied niches and the effective area per species. It allows positive and negative relationships only as special cases. We sampled 3715 deadwood objects on 135 plots along a forest structure gradient in the Black Forest, Germany, and recorded 284 wood‐inhabiting fungal species. To assess heterogeneity of deadwood structures, we calculated two multidimensional structural diversity indices: Structural richness was used as a measure of available niche space, and structural divergence as a measure of multivariate variance within that niche space. Those indices were then related to species richness estimates for rare, common and dominant species using the framework of Hill numbers. We found a linear, positive effect of structural richness and a unimodal effect for structural divergence on estimated species diversity. Structural richness, but not structural divergence, was strongly correlated with the number of sampled deadwood objects. No clear differences between the responses of rare, common and dominant species to the two heterogeneity gradients were found. We also estimated the mean abundance as a proxy for mean population size, which decreased significantly with structural richness but was non‐significantly related to structural divergence. Synthesis. In general, the results of this study suggest a unimodal heterogeneity–diversity relationship for deadwood‐inhabiting fungi and are thereby in line with the area‐heterogeneity trade‐off hypothesis. Thus, the negative effect of heterogeneity should lead to lower species richness and a higher risk of stochastic extinctions at high levels of heterogeneity. However, as deadwood amount and deadwood diversity are often strongly correlated, we argue that the positive effect of resource availability on species richness may mask the negative effect of structural heterogeneity in some cases.

A Modelling System for Dead Wood Assessment in the Forests of Northern Eurasia

Dead wood, including coarse woody debris, CWD, and fine woody debris, FWD, plays a substantial role in forest ecosystem functioning. However, the amount and dynamics of dead wood in the forests of Northern Eurasia are poorly understood. The aim of this study was to develop a spatially distributed modelling system (limited to the territories of the former Soviet Union) to assess the amount and structure of dead wood by its components (including snags, logs, stumps, and the dry branches of living trees) based on the most comprehensive database of field measurements to date. The system is intended to be used to assess the dead wood volume and the amount of dead wood in carbon units as part of the carbon budget calculation of forests at different scales. It is presented using multi-dimensional regression equations of dead wood expansion factors (DWEF)—the ratio of the dead wood component volume to the growing stock volume of the stands. The system can be also used for the accounting of dead wood stock and its dynamics in national greenhouse gas inventories and UNFCCC reporting. The system’s accuracy is satisfactory for the average level of disturbance regimes but it may require corrections for regions with accelerated disturbance regimes.

Does monitoring of saproxylic beetles benefit from inclusion of larvae?

Abstract Saproxylic beetles (Coleoptera) are important for biomonitoring to evaluate the state of ecological conservation of forest ecosystems. However, beetle larvae are rarely considered due to their difficult identification. Here, we evaluate the use of beetle larvae, alongside adult specimens, for monitoring. Forty sifting samples from deadwood structures were analysed from eight different forest sites near Münster (Germany). Larvae were identified by matching with DNA sequences (COI) of identified adults (from GBOL database/BOLD) using various standard DNA‐based species delimitation methods. Our main objective was to figure out whether larvae can be sampled, barcoded, and identified successfully on a larger scale, and whether the inclusion of larval data improved the ecological and taxonomic results of the survey. Altogether we found 129 species as larvae and 313 as imagos. Four larva species could not be identified to species level because of a lack of a match with adult reference sequences. Among all sifting samples, 41% of the species recorded as larva were not found as imago. The inclusion of larvae increased the expected species richness and generated a more precise differentiation between the sites in respect of saproxylic species richness and assemblage composition. Moreover, almost 30% of identified larvae are not morphologically described, so they cannot be identified morphologically. This study showed that the use of larvae could considerably improve the accuracy of ecological surveys, particularly at meso‐ and microhabitat level, while for higher level, geographical scales sequencing and sampling efforts would be at the moment excessive.

Habitat use of Bechstein’s Bat (Myotis bechsteinii) and woodpeckers reveals the importance of old-growth features in European beech forests

Old-growth forests provide valuable habitats for bat and woodpecker species worldwide. However, the abundance of old-growth related habitat features is frequently reduced in managed forests. Bechstein’s Bat (Myotis bechsteinii, Kuhl 1817) is globally restricted to old-growth deciduous forests in Europe and therefore a species of high European conservation priority. Since the species prefers woodpecker cavities for roosting, woodpeckers are keystone species for Bechstein’s Bat. We surveyed woodpecker activity and forest structural features within 16 roost sites of Bechsteińs Bat and a random sample from the surrounding managed forest within the centre of the global distribution of Bechsteińs Bat. We found above-average quantity of old-growth related habitat features in the roost sites of Bechstein’s Bat. Five of six occurring woodpecker species revealed significantly higher densities in the roost sites of Bechstein’s Bat, demonstrating a distinct preference of the woodpeckers and the bat in managed forests for old, deciduous stands with high basal areas of large living trees (DBH > 50 cm), bearing deadwood structures and highest available tree cavity densities. Furthermore, when comparing the direct surroundings of roost trees to their wider surroundings (16 ha), cavity density and other old-growth features reached their maxima in the direct surroundings of roost trees (mean = 19.3 cavities ha−1), demonstrating a distinct habitat selection of Bechsteińs Bat for patches with maximum available cavity density on large and fine spatial scale. We found a close relation between the basal area of trees with limb break offs (>20 cm base diameter) and tree cavity density, which leads us to the conclusion that specifically injured but still vital, large trees play a major role for the development and long-term persistence of tree cavities. Finally, our analyses revealed a threshold of 20 (DBH > 50 cm) or 10 (DBH > 70 cm) large deciduous trees bearing deadwood structures per ha to fulfil the minimum habitat requirements of the woodpeckers and Bechstein’s Bat. Obviously, Bechsteińs Bat and the associated woodpeckers explicitly selected forest patches, which most closely resembled primeval forest benchmarks, emphasising the importance of maintaining and developing forest patches, providing the mentioned habitat features within managed forests.

Standing dead trees as indicators of vertebrate diversity: Bringing continuity to the ecological role of senescent trees in austral temperate forests

Standing dead trees are known to house diverse assemblages of vertebrates in temperate forests worldwide. In temperate austral forests of South America, however, the functional role of dead trees has been mostly focused on cavity provision, but other functions remain poorly understood. Thus, we conducted a preliminary study examining the effect of dead trees on the taxonomic diversity of vertebrates in South American temperate forests. Diversity metrics estimated from rarefaction curves and community data augmentation showed that taxonomic diversity of vertebrate species was equal between dead and living trees. Habitat variables equally affected species diversity of vertebrates in dead and living trees. Tree height and elevation had a positive effect while forest cover negatively affected species diversity. The similar diversity and composition of vertebrates found in living and dead trees suggests dead trees are equally valuable for conservation. In austral forests dominated by long-living tree species, the death of a tree is a long process involving the retention of several microhabitats once the tree dies and the enrichment of deadwood structures attracting saproxylic organisms. These findings highlight the need of establishing minimum stocks of dying and senescent trees for achieving ecosystem integrity.

The Abundance and Structure of Deadwood: A Comparison of Mixed and Thinned Chinese Fir Plantations.

The sustainability of coniferous monoculture plantations is facing challenges with respect to yields, ecology, and biodiversity. Conversion of monocultural coniferous plantations into mixed stands using thinning or direct mixed planting is widely considered to be a key strategy for overcoming these challenges and transforming the characteristics of plantations on a regional scale. Substantial amounts of deadwood may be produced in mixed forests (MFs); this material is important for evaluating and modifying forest management methods, understanding the dynamics of forest stands, and achieving biodiversity conservation. We assessed the quantitative characters and diameter distributions of deadwood in mixed and thinned Chinese fir [Cunninghamia lanceolata (Lamb.) Hook.] forests over one rotation. We used the g(r) function and spatial parameters to analyze the spatial structure of deadwood, and used logistic regression and Hegyi’s competition index (HCI) to explore competition and mortality. Our results indicate that: (1) Chinese fir dominated in all groups of deadwood (snags, broken wood, and fallen wood), and the abundance, volume, and mortality rates of deadwood were much lower in the thinning forest compared to the MF. (2) Later coming populations (LCPs) comprised the majority of the small diameter classes in the thinning forest, but only accounted for a small proportion of the MF. (3) Broken wood in the thinning forest was randomly distributed, while the other types of deadwood were clustered at most spatial scales. In contrast, the spatial patterns in the MF were random at most spatial scales. (4) Total deadwood in both stands was in a status of intermediate and was randomly surrounded by its four nearest neighbors. All types of deadwood were highly mixed in the thinning forest and moderately mixed in the MF. Our case study suggests that thinning and mixing result in different stand development processes and thus influence the type, amount, and structure of deadwood. Thinning significantly reduces competition, which is the main driver of tree mortality. Converting pure Chinese fir plantations into mixed stands by thinning should be taken in future. Understanding tree mortality after conversion is essential to select appropriate silvicultural treatments and achieve ultimately sustainable forest management.

Spatial patterns of bat diversity overlap with woodpecker abundance.

Woodpecker diversity is usually higher in natural forests rich in dead wood and old trees than in managed ones, thus this group of birds is regarded as an indicator of forest biodiversity. Woodpeckers excavate cavities which can be subsequently used by several bird species. As a consequence, their abundance indicates high avian abundance and diversity in forests. However, woodpecker-made holes may be also important for other animals, for example, mammals but it has seldom been investigated so far. Here, we examine how well one species, the Great Spotted Woodpecker, predicts species richness, occurrence and acoustic activity of bats in Polish pine forests. In 2011 we conducted woodpecker and bat surveys at 63 point-count sites in forests that varied in terms of stand age, structure and amount of dead wood. From zero to five Great Spotted Woodpeckers at a point-count site were recorded. The total duration of the echolocation calls during a 10-min visit varied from 0 to 542 s and the number of bat species/species groups recorded during a visit ranged between zero to five. The local abundance of the woodpecker was positively correlated with bat species richness (on the verge of significance), bat occurrence and pooled bat activity. The occurrence of Eptesicus and Vespertilio bats and Nyctalus species was positively related with the abundance of the Great Spotted Woodpecker. The activity of Pipistrellus pygmaeus, Eptesicus and Vespertilio bats and a group of Myotis species was not associated with the woodpecker abundance, but echolocation calls of Nyctalus species, P. nathusii and P.pipistrellus were more often at sites with many Great Spotted Woodpeckers. Moreover, the probability of bat presence and the activity of bats was generally higher shortly after dusk and in middle of the summer than in late spring. We suggest that the observed correlations can be driven by similar roosting habitats (e.g., woodpeckers can provide breeding cavities for bats) or possibly by associated invertebrate food resources of woodpeckers and bats. The abundance of Great Spotted Woodpecker seems to be a good positive indicator of bat species richness, occurrence and activity, thus adding a group of relatively cryptic forest species that are indicated by the presence of the Great Spotted Woodpecker.

Structure and Dynamics of Deadwood in Pine and Oak Stands and their Role in CO2 Sequestration in Lowland Forests of Central Italy

There are many data values describing deadwood in primary forests, however, there is much less information concerning managed forests, particularly in the Mediterranean area. Whole non-living woody biomass (deadwood) is the main component of forest types that plays a vital role in improving and maintaining biodiversity. The dynamics of deadwood and CO2 sequestration by deadwood were examined in three Mediterranean lowland forests: pine forest Pinus pinea L.), evergreen oak forest (Quercus ilex and Quercus suber L.), and deciduous oak forest (Quercus cerris L.). The aim of this study was to carry out a quantitative and qualitative evaluation of the deadwood to gather useful information for the Mediterranean forest management, and to provide some useful data that can be integrated into the methods of estimation for carbon stored in dead components of Mediterranean forest types. The investigations focused on the characterization of the deadwood, to determine which traits are dominant and their potentially functionality within the forest type. Results indicated the deciduous oak type had the highest amount of stand volume (379 m3/ha), deadwood volume (161.8 m3/ha), and C storage (31.43 t/ha). The major component of dead wood was the standing dead trees or snags. There was a higher volume of deadwood in the deciduous oak forest than in the pine and evergreen oak forests. In addition, the deciduous oak forest had a higher snag creation index, a higher fallen log creation index, and a higher past management index compared to pine and evergreen oak forest types. Deadwood volume increased as the decay class in the deciduous oak forest increased, while this trend decreased in the evergreen oak and pine forests. The amount of deadwood was affected by the forest type and forest management regime. Dynamic and past management of deadwood indices indicated that their structure was still in the initial phase of creation and decay in the pine and evergreen oak forests. A comparison with other studies on similar forest types brought out that the variation range of the main parameters for the management of deadwood fell within the variation of the parameters studied. However, the values of these parameters cover a broad range. The population of each forest type is extremely sensitive to the different evolutionary periods of the forest dynamics.

Using the visitor-employed photography method to analyse deadwood perceptions of forest visitors: a case study from Bavarian Forest National Park, Germany

This study investigates visitors’ perceptions and preferences regarding the characteristics of deadwood in the Bavarian Forest National Park (SE-Germany). Visitor-employed photography has been used to collect information about visitors’ preferences. Deadwood is the second most photographed forest element which underlines its important role in forest perception. Even though deadwood photographs are evaluated significantly worse than most other forest elements, most visitors nevertheless associate deadwood photographs with a positively rated forest image. Based on the relationship between aesthetics and recreation revealed in the interviews, it can be concluded that the forest path during the hike was both pleasant and restful. This is confirmed by the post-trip interviews, showing that a higher proportion of deadwood is associated with more aesthetics or recreational value. Regarding deadwood structure results show that deadwood fragments and debris are perceived negatively, while root stocks were assessed more positively. We also found a gradient with positive evaluations increasing with progressing decomposition.

Accurate forest projections require long-term wood decay experiments because plant trait effects change through time.

Whether global change will drive changing forests from net carbon (C) sinks to sources relates to how quickly deadwood decomposes. Because complete wood mineralization takes years, most experiments focus on how traits, environments and decomposer communities interact as wood decay begins. Few experiments last long enough to test whether drivers change with decay rates through time, with unknown consequences for scaling short-term results up to long-term forest ecosystem projections. Using a 7 year experiment that captured complete mineralization among 21 temperate tree species, we demonstrate that trait effects fade with advancing decay. However, wood density and vessel diameter, which may influence permeability, control how decay rates change through time. Denser wood loses mass more slowly at first but more quickly with advancing decay, which resolves ambiguity about the after-life consequences of this key plant functional trait by demonstrating that its effect on decay depends on experiment duration and sampling frequency. Only long-term data and a time-varying model yielded accurate predictions of both mass loss in a concurrent experiment and naturally recruited deadwood structure in a 32-year-old forest plot. Given the importance of forests in the carbon cycle, and the pivotal role for wood decay, accurate ecosystem projections are critical and they require experiments that go beyond enumerating potential mechanisms by identifying the temporal scale for their effects.

Estimation of coarse dead wood stocks in intact and degraded forests in the Brazilian Amazon using airborne lidar

Abstract. Coarse dead wood is an important component of forest carbon stocks, but it is rarely measured in Amazon forests and is typically excluded from regional forest carbon budgets. Our study is based on line intercept sampling for fallen coarse dead wood conducted along 103 transects with a total length of 48 km matched with forest inventory plots where standing coarse dead wood was measured in the footprints of larger areas of airborne lidar acquisitions. We developed models to relate lidar metrics and Landsat time series variables to coarse dead wood stocks for intact, logged, burned, or logged and burned forests. Canopy characteristics such as gap area produced significant individual relations for logged forests. For total fallen plus standing coarse dead wood (hereafter defined as total coarse dead wood), the relative root mean square error for models with only lidar metrics ranged from 33 % in logged forest to up to 36 % in burned forests. The addition of historical information improved model performance slightly for intact forests (31 % against 35 % relative root mean square error), not justifying the use of a number of disturbance events from historical satellite images (Landsat) with airborne lidar data. Lidar-derived estimates of total coarse dead wood compared favorably with independent ground-based sampling for areas up to several hundred hectares. The relations found between total coarse dead wood and variables quantifying forest structure derived from airborne lidar highlight the opportunity to quantify this important but rarely measured component of forest carbon over large areas in tropical forests.

Medium‐term effects of active management on the structure of mature Douglas‐fir (Pseudotsuga menziesii) stands

AbstractWe developed an observational study to (1) examine differences in the structure of mature Douglas‐fir stands representing thinned, structural retention harvest and unmanaged conditions, and (2) assess the extent to which active management in mature stands expedites development of old‐growth structure, relative to two old‐growth indices. Time since treatment averaged 38 and 22 yr in thinned and retention harvest conditions, respectively, and stand age ranged from 106 to 193 yr when sampled. Differences in stand structure were apparent between all three management conditions, with attributes associated with stumps, live tree diameter diversity, understory vegetation, and vertical foliage structure being the strongest individual drivers of these differences. Mean old‐growth index scores were lower than expected of true old‐growth for each of the management conditions examined here, but were not significantly different between thinned and unmanaged stands. Our results suggest thinning in mature stands may promote certain elements of old‐growth structure, including foliage height diversity, but also indicate the need for provisions against the depletion of dead wood resources. Stumps are an understudied dead wood structure, and in actively managed mature stands, our results imply that stumps may provide a degree of functional substitution where down log availability is low.

Saving species, time and money: Application of unmanned aerial vehicles (UAVs) for monitoring of an endangered alpine river specialist in a small nature reserve

The increasing importance of conservation and restoration of our natural capital is associated with a growing demand for reliable and cost-effective scientific data to support decision making and monitoring of implemented measures. Such data include information about habitats, abiotic conditions and disturbances. The small extent or small-scale structure of most restoration sites requires a high spatial resolution exceeding that provided by standard satellite imagery. When the site is still unstable during the initial phase or when frequent disturbance is expected, additionally a high temporal resolution is required. In this case study, we demonstrate the usefulness of a UAV (unmanned aerial vehicle) for monitoring river and floodplain restoration based on a conservation project aimed to preserve Germany's last remaining population of the highly endangered alpine river plant C. chondrilloides. This population is confined to a small, 5 ha area within a highly dynamic alluvial fan in the Bavarian Alps. We used the data acquired by UAV to monitor stream channel dynamics, to quantify bedload transport, erosion and deadwood structures and to characterize vegetation cover and height with the aim of identifying types and loss of habitats and consequently estimating extinction risk. The results show a highly dynamic stream channel and considerable bedload transport and erosion between flood events. The majority of the remaining C. chondrilloides population is found on terraces which are prone to erosion and escape habitats are missing. Between 2016 and 2017 we documented a loss of almost 25% of the species' potential habitats due to erosion events. Three percent of the existing population was lost to those events. Substantial spread of the species was only at the edge terrace which is subject to a high risk of extinction. Our study further demonstrates that many important parameters for the implementation of evidence-based conservation can be easily and cost-effectively derived from standard RGB images taken by UAVs and GIS software. As a consequence, we encourage the increased use of UAVs for restoration and monitoring practice.

Comparing the Quantity and Structure of Deadwood in Selection Managed and Old-Growth Forests in South-East Europe

The knowledge about the impact of selection silviculture on deadwood components is fairly scarce. This study compared two Dinaric old-growth forests (OGFs) with adjacent managed forests (MFs) in which the single-tree selection system has been applied for a century. The comparisons were made in terms of the current amounts of coarse woody debris (CWD), distribution of its decay stages, and diameter structure of different CWD types (snags, logs, stumps). The relationship between the volume of live and dead trees was also examined. In both OGFs and MFs, the most snags were found in the third decay stage, while the volume of logs and stumps increased from the first to fifth decay class. The study showed the clear advantage of OGFs over adjacent selection MFs in terms of CWD volume, whereas the basal area of live trees and growing stock were not always reliable indicators for distinguishing between MFs and OGFs. The diameter distribution of individual CWD types (snags, logs, stumps) also differed significantly between selection MFs and OGFs in all tested pairs. This fact, along with the significant differences in CWD volume, indicates that selection silviculture should be amended to incorporate practices that ensure more natural management of deadwood components.

Can large unmanaged trees replace ancient pollarded trees as habitats for lichenized fungi, non-lichenized fungi and bryophytes?

Management of ancient trees constitutes a major dilemma in the conservation of associated biodiversity. While traditional methods are often advocated, such practices may incur considerable costs and their effects have rarely been scientifically evaluated. We compared the communities of lichenized fungi, non-lichenized fungi, and bryophytes among equal number of coarse previously pollarded and unmanaged trees (n = 340). On 400 Ulmus glabra and 280 Fraxinus excelsior trees at 62 sites in Norway, we found 209 lichenized fungi, 128 non-lichenized fungi, and 115 bryophytes. Pollarded trees were richer in microhabitats than unmanaged trees and had significantly higher richness of bryophytes (ash) and non-lichenized fungi (ash and elm), the latter increasing with the availability of dead wood, cavities and coarse bark structure in pollarded trees. Further, the average total number of red-listed species, and red-listed lichenized fungi separately, were significantly higher on pollarded versus unmanaged trees, with diversity related to trunk circumference, depth of bark fissures and number of cavities. Our results underline the importance of microhabitats associated with old trees, but we cannot establish with certainty the importance of pollarding per se. Since we did not find any negative effect of canopy cover for community diversity, we assume that old trees with rich epiphytic communities can develop without management intervention. The high share (37 out of 49) of red-listed species occurring on unmanaged trees, and the fact that 11 red-listed species were found exclusively on unmanaged trees, may further indicate that unmanaged trees can with time replace the ancient pollarded trees as habitats for rich cryptogamic communities.

Structure and Spatial Distribution of Dead Wood in Two Temperate Old-Growth Mixed European Beech Forests

Old-growth forests are often looked at as reference for close to nature silviculture, which aims to manage forests in a natural way. An important component of these forests is the large amount of deadwood they possess; the role of dead wood in the forest ecosystem has been well recognised. A detailed investigation of dead wood characteristics (the amount per stand, species, dead wood type, decay class, size and spatial distribution) was performed in two Romanian old-growth European mixed beech forests: Runcu Grosi Reserve (sessile oak-beech) and Sinca (silver fir-beech). Dead wood pieces were classified as belonging to one of seven dead wood types and one of five decay classes. The total amount of the dead wood was greater in Runcu Grosi (240.8 m3 ha-1) than in Sinca Forest (135.5 m3 ha-1). The majority of the dead wood in Runcu Grosi was composed of sessile oak (91.7%), whereas in Sinca Forest, the main dead wood species was silver fir (67.0%); both species exhibited higher values of probability density than beech, the second most important species. The dead wood exhibited much variation in tree size and in dead wood type, and covered the entire spectrum of decomposition classes. The main spatial pattern of all standing dead trees was random in both forests (over 55%), with a reduced participation of regularity and aggregation. The results of this investigation could be used as key values derived from natural conditions to enhance the biodiversity related to dead wood in managed temperate beech mixed forests.

Is it Worth the Money? The Functionality of Engineered Shallow Stream Banks as Habitat for Juvenile Fishes in Heavily Modified Water Bodies

AbstractHeavily modified water bodies (HMWB) are characterized by monotonous and straightened channel morphologies with high degrees of bank enforcement. They often lack shallow bank habitats, which are considered important for critical life stages of fishes. In this study, three principle options to engineer shallow stream zones were assessed concerning the value of the created habitats for larval, juvenile and adult stages of fishes in 30 sites from three HMWB. The construction scheme of the juvenile habitats comprised different degrees of embankment ranging from rip‐rap structures with steep bank angles to almost nature‐like construction schemes with very flat river‐banks and sparing usage of structural enrichment such as boulders and dead wood. In general, the differences between the three habitat types were more pronounced in density of different life stages than in the presence or absence of species or certain life stages. A steep bank angle and a high degree of engineering such as placement of rip‐rap embankment, boulders or dead wood structure in the habitats were hardly accepted by early larval and juvenile stages of rheophilic fishes. In contrast, the construction scheme of a nature‐like habitat with a flat bank angle (<10%), low water depth (mean = 24 cm) and a sparing usage of coarse woody debris (CWD) and boulders had the highest success. Other investigated habitat types did not provide additional benefit, neither in terms of supporting additional species and life stages, nor in high individual numbers and should thus only be implemented when land for restoration is scarce and nature‐like habitats cannot be realized. Copyright © 2016 John Wiley & Sons, Ltd.

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.

Dead wood quality influences species diversity of rare cryptogams in temperate broadleaved forests

Dead wood is one of the most important indicators of forest naturalness and the most important manageable habitat for biodiversity in forests. Standing and lying dead wood, and especially coarse woody debris, plays an important part in creating habitats for many highly specialized organisms, e.g., insects, fungi, lichens and bacteria. Temperate mixed deciduous forests, rich in species, have been studied only to a small extent from the point of view of the ecology of wood-related cryptogams. Our study aimed at the reduction of the gap in knowledge about the ecological characteristics of dead wood-dependent organisms by focusing on species of cryptogams developing on various dead wood structures typical of temperate non-beech forests. Studies were performed in forests located in Lithuania, Poland, Belarus and Russia. We recorded 48 species of cryptogams: 18 species of bryophytes, 24 species of fungi and 6 species of lichens developing on dead wood. Our study stresses the importance of all types of dead wood as a substrate for the development of rare cryptogam species. Logs were the most important substratum type for cryptogams, followed by snags, dead trees and stumps. The cryptogam species richness on logs was several times higher than on the three other types of substrata. Coarse logs of intermediate decay stages hosted the highest number of cryptogams, followed by freshly fallen logs and, finally, well decayed logs. Assessing the importance of dead wood quality for the studied cryptogams, we found that intermediate decay stages are extremely important for fungi, while bryophytes or lichens do not show a clear preference. The highest number of cryptogams was found on Fraxinus excelsior, Quercus robur and Picea abies, while other tree species had less than half cryptogam species.

How does deadwood structure temperate forest bat assemblages?

Thirty percent of forest species depend on deadwood. Some of them are now considered rare or at high risk of extinction mainly due to an insufficient quantity of deadwood substrates. Some bats roost in dead trees and snags. Because European bats are strictly insectivorous, we can wonder whether deadwood plays an important role by providing potential preys too. We conducted ultrasonic surveys in different deciduous French forests dominated by oaks (Quercus spp.) and beech (Fagus sylvatica). Our results showed a positive relationship between the volume of deadwood and the richness of bat species. Some species were positively related to deadwood volumes, either lying or standing, with detected thresholds. Species richness increased particularly from 25 m3 per hectare of standing deadwood. This link can be explained by deadwood-dwelling preys or by changes in the forest structure, due to openings created by dead trees that are favorable for edge-habitat species. Other species negatively reacted to the presence of deadwood, either because bats were not able to forage there or because dead trees did not provide relevant preys. Contrary to our hypothesis, clutter by foliage and basal area of the living trees explained more the presence/occurrence of gleaning bats than deadwood. Whereas several species were considered as forest bats (Myotis bechsteinii, Plecotus auritus, Barbastella barbastellus), we did not find any relationship between their occurrence and deadwood. This result strengthens the need of further studies on the relationships between forest habitats and bat assemblages.