Dead Wood Quality Research Articles

Will stumps from forest thinning and other standing deadwood provide habitat for saproxylic beetles if felling stumps on clearcuts are harvested?

ABSTRACT Increased level of stump harvest on clearcuts is expected due to growing demand for bioenergy. For saproxylic species, this will reduce habitat supply. Negative effects on populations may be buffered by alternative deadwood habitats, especially stumps after forest thinning. We investigated clearcuts and mature forest to see whether such stumps or other standing deadwood could host saproxylic beetles that occur in clear-felling stumps. The study was conducted in boreal Sweden, on clearcuts 3–14 years after harvest and in mature forests. Beetles were sampled from the bark of spruce, pine and birch, from stumps after clear-felling, stumps after thinning, snags within forests and high-stumps on clearcuts. Beta diversity differed significantly between deadwood types, but not tree species. The stumps after thinning had a species poor assemblage compared to other deadwood. Abundance of common species was higher in deadwood on clearcuts compared to forests, and higher in snags than in stumps. We conclude that stumps after thinning and other standing deadwood will not buffer habitat loss from increased stump harvest for species inhabiting stumps on clearcuts, because these communities require sun-exposed habitats. Within mature managed forests, improving the quality and diversity of deadwood will be important for increasing the diversity of saproxylic beetle communities.

Harmonized decay classification for dead wood in Nordic national forest inventories

ABSTRACT Dead wood quality is typically recorded as a biodiversity indicator and as part of forest carbon estimates, using decay classification systems. In large-scale national forest inventories (NFIs), these systems typically differ among countries. Harmonizing them would allow analyzes over broader scales and the use of larger data sets. Here, we exemplified the development of a harmonized decay classification for the NFIs of Finland, Norway, and Sweden, using wood density as an objective harmonizing criterion. We sampled 441 Scots pine, Norway spruce, birch and trembling aspen in different conditions and decay classes, measured their density and developed the harmonized classification for each species and dead wood type (standing and fallen). The assignments relied on minimizing within-class variance in wood density in the harmonized classes. Assigned into three (standing dead wood) and four (fallen dead wood) classes, the harmonization led to modest losses of information, especially in the advanced decay stages. How the original decay classes were assigned into the harmonized classes differed slightly, depending on the tree species and type. This is an advantage over the expert assessment that typically treat all species and types of dead wood the same way despite clear differences in decomposition pathways.

Factors influencing the diversity of deadwood, a crucial microhabitat for many rare and endangered saproxylic organisms

Deadwood (DW) is a crucial component of habitats, with both its volume and diversity considered critical for saproxylic organisms. Deadwood position, thickness, snag height, species composition, and decay stage were studied in the context of eight factors characterizing habitats, stands, and management types. A multivariate multiple regression model was used to analyze data from 29,098 sample plots.Deadwood diversity (a 5-dimensional dependent variable) was found to strongly depend on DW volume in a given area and on the species composition of the stand. A less pronounced effect was exerted by site fertility and moisture, the age and DBH structure of the stand, and terrain type. The model also revealed that the location of the stand in managed or unmanaged areas did not have a direct impact on deadwood diversity, with stand features being more important.Analysis of individual qualitative characteristics showed that DW thickness was affected by the same seven factors as DW diversity. DW position and decay stage were influenced by four factors: site fertility and moisture as well as stand age and species composition. In addition to the species composition of stands, DW species composition was positively influenced by more fertile and moist sites and a more varied DBH structure of stands. A significant negative effect was identified for high DW volume, which indicates that the deadwood accumulated in a stand tends to be derived from the tree species that was most vulnerable to mortality at a given time. Snag height variation was influenced by such stand characteristics as age, DBH structure, and species composition; the other significant factors were DW volume and terrain type. The diversity levels of individual DW characteristics were significantly and positively correlated, which means that all of them often revealed high or low diversity at the same time.Our study showed that forests with low DW volume additionally face the problem of DW quality. Thus, efforts to increase DW volume should be focused on those DW characteristics that are lacking (large trees, species diversity, and height variation of snags). DW diversity is lower in younger stands, with little DBH variation, and in forests which are more easily accessible, located mostly in the lowlands, and growing on less fertile and dry or mesic sites.

Determining structure and volume of the European beech (Fagus sylvatica L.) deadwood in managed stands in the Rodopi Mountain Range National Park, Greece

Abstract The multifaceted role of deadwood in forest ecosystems has been widely recognized while it is regarded as an indicator of sustainable forest management. Nevertheless, there are hardly any data on deadwood volume and structure in managed forests in Greece. The study took place in beech forests of the Western and Central part of the Rodopi Mountain Range. The objective was to determine the amount, variability and quality of deadwood and to compare it with data from managed as well as natural forests. Data were collected on 30 randomly distributed circular plots of 0.1 ha. The results showed that the average deadwood amount (13.46 m3 ha−1) was much lower compared to that recorded in other European forests and they highlighted the absence of large dead standing trees due to the management regime. The deadwood quality showed great variation in stages of decay.

Stem traits, compartments and tree species affect fungal communities on decaying wood.

SummaryDead wood quantity and quality is important for forest biodiversity, by determining wood‐inhabiting fungal assemblages. We therefore evaluated how fungal communities were regulated by stem traits and compartments (i.e. bark, outer‐ and inner wood) of 14 common temperate tree species. Fresh logs were incubated in a common garden experiment in a forest site in the Netherlands. After 1 and 4 years of decay, the fungal composition of different compartments was assessed using Internal Transcribed Spacer amplicon sequencing. We found that fungal alpha diversity differed significantly across tree species and stem compartments, with bark showing significantly higher fungal diversity than wood. Gymnosperms and Angiosperms hold different fungal communities, and distinct fungi were found between inner wood and other compartments. Stem traits showed significant afterlife effects on fungal communities; traits associated with accessibility (e.g. conduit diameter), stem chemistry (e.g. C, N, lignin) and physical defence (e.g. density) were important factors shaping fungal community structure in decaying stems. Overall, stem traits vary substantially across stem compartments and tree species, thus regulating fungal communities and the long‐term carbon dynamics of dead trees.

Evidence of the association between deadwood and forest recreational site choices

The level of biodiversity is in decline, also in forests. As more natural structures are known to safeguard biodiversity, changes in forest management, including higher amounts of deadwood, may help reverse the decline. However, this could lead to trade-offs between forest ecosystem services, and forest recreation might be negatively affected by the presence of more natural forest structures, especially deadwood. So far, only a few studies have investigated the influence of deadwood on recreation in larger forest areas and on a national or regional scale. To better understand the possible impact, we analysed how higher amounts and different forms of deadwood would affect site preferences for recreation employing an online survey based on a representative sample in Bavaria, Germany (N = 1462). A choice experiment comprising different forest alternatives with varying degrees of deadwood showed that the amount of deadwood does not influence respondents' choice of recreation sites. However, deadwood quality attributes, i.e. structural variety and advanced decomposition positively impacted site choices. Latent class models revealed both observed and unobserved taste heterogeneity. Deadwood was, however, not an essential attribute for the forest site-selection, while infrastructure facilities or good paths/accessibility were more important. The results show that no significant trade-offs between forest recreation and deadwood enrichment exist. At the same time, respondents showed solid preferences for improving habitats for rare and endangered species in forests, indicating that biodiversity is significant to them. As the preferences for a mixture of standing and lying structures also coincide with conservation ecology research, we conclude that conflicts between recreationists and increased occurrence of deadwood to promote biodiversity are not that severe as often assumed by forest managers.

Dead wood diversity promotes fungal diversity

Dead wood is a source of life as it provides habitat and substrate for a wide range of fungal species. A growing number of studies show an important role of wood quality for fungal diversity, but in most cases for a limited number of wood traits or tree species. In this study, we evaluate how abiotic and biotic factors affect the fungal diversity and composition during dead wood decomposition. For ten common European tree species, fresh similar‐sized logs were incubated simultaneously in two Dutch forests. Annual surveys of fungal fruiting bodies were made for an 8‐year period. For each tree species, 20 fresh stem traits were measured that are important for chemical and physical defence and for nutritional quality. Throughout eight years, 4644 fruiting bodies belonging to 255 species and 90 genera were recorded on the logs of ten tree species. Fungal frequency and richness were higher for Angiosperms than for Gymnosperms, both for individual tree species and as a group, and higher for tree species with more acquisitive stem trait strategies (i.e. high nutritional value and low physical defence). Differences in fungal communities were strongly driven by phylogenetic group (Gymnosperms versus Angiosperms), stem traits, decay time and forest sites, together explaining 23% of the variation. Fungal communities in sandy site diverged early in the decay process but converged later because of substrate homogenization. Of the 128 fungal species included in the analyses, 41% showed a preference for specific tree species and 34% for a specific successional year. In conclusion, dead wood quality, determined by tree species and decay stage, is an important driver of fungal diversity. For forest management, promoting a wide array of dead tree species (especially angiosperm species), a range of stem trait values and decay stages will increase fungal and, thereby, forest biodiversity.

Dynamic feedbacks among tree functional traits, termite populations and deadwood turnover

Abstract Changes in the composition of plant functional traits may affect ecosystem processes through influencing trophic interactions. Bottom‐up control by plant species through food availability to animals may vary with time. However, such dynamics and their consequences for deadwood turnover are poorly known for detrital food webs. We introduce a dynamic conceptual model of the feedback of tree functional traits, (deadwood‐feeding) termite populations and deadwood decomposition. We hypothesized that tree functional diversity (in terms of a wood resource economic spectrum [WES]) supports the sustenance of termite populations via complementary food supplied through time, as deadwood varies in traits both initially across species and because of different decomposition rates. Simultaneously, driven by this temporal dynamics of food quality, the consumption of deadwood by termites should hypothetically sustain deadwood turnover in a functionally diverse forest over time. We tested our hypothesis through an 18‐month termite‐exclusion decomposition experiment by incubating coarse (i.e. 5 cm diameter) deadwood of 34 woody species in two subtropical forests in East China. One site still sustained a healthy population of pangolins as the keystone termite predator, whereas another had lost its pangolins due to hunting and illegal wildlife trade. The results supported our hypothesis: in the first 12 months, termites amplified the positive linear relationship between % wood mass loss and initial wood quality (WES). In contrast, between 12 and 18 months, termite‐mediated consumption, and associated wood mass loss, showed a humpback relation with the initial WES. This shift in termite preference of deadwood species along the WES reflects complementary food availability to termites through time. Synthesis. Our findings imply that tree functional composition, with variation in deadwood quality through decomposition time, can help to sustain termite populations and thereby forest carbon turnover. Future studies need to test whether and how our conceptual model may apply to other detrital systems and food webs. In general, food web research would benefit from a stronger focus on temporal patterns for better understanding the interactions of basal resource functional traits and consumers on ecosystem functions.

Deadwood volume and quality in recreational forests: the case study of the Belgrade forest (Turkey)

Aim of the study: The aim of this study is to understand quantitative and qualitative characteristics of deadwood in recreational forests.Area of study: Belgrade forest in the North of Istanbul city (Turkey).Material and methods: The data has been collected through a stratified sampling scheme that has randomly located 50 clusters formed by 3 sample plots each (150 sample plots).Main results: The results show an average deadwood volume of 16.49 m3 ha-1 (81.5% in logs, 16.4% in snags, 2.1% in stumps). The highest volume of deadwood is in oldest forests (age over 180 years) with an average value of 20.39 m3 ha-1, followed by forests with 61-120 years with 15.77 m3 ha-1. Concerning forest management objectives, the results show that average deadwood volume is 13.66 m3 ha-1 in the forest section managed for water resource conservation and 21.14 m3 ha-1 in the forest section managed for recreational purposes.Research highlights: Deadwood management in the recreational forests must consider both biodiversity conservation and recreational attractiveness of an area.Keywords: forest management; forest types; forest accessibility; stand age; wood decomposition rate.

Modeling of Dead Wood Potential Based on Tree Stand Data

Here we present a framework for identifying areas with high dead wood potential (DWP) for conservation planning needs. The amount and quality of dead wood and dying trees are some of the most important factors for biodiversity in forests. As they are easy to recognize on site, it is widely used as a surrogate marker for ecological quality of forests. However, wall-to-wall information on dead wood is rarely available on a large scale as field data collection is expensive and local dead wood conditions change rapidly. Our method is based on the forest growth models in the Motti forest simulator, taking into account 168 combinations of tree species, site types, and vegetation zones as well as recommendations on forest management. Simulated estimates of stand-level dead wood volume and mean diameter at breast height were converted into DWP functions. The accuracy of the method was validated on two sites in southern and northeastern Finland, both consisting of managed and conserved boreal forests. Altogether, 203 field plots were measured for living and dead trees. Data on living trees were inserted into corresponding DWP functions and the resulting DWPs were compared to the measured dead wood volumes. Our results show that DWP modeling is an operable tool, yet the accuracy differs between areas. The DWP performs best in near-pristine southern forests known for their exceptionally good quality areas. In northeastern areas with a history of softer management, the differences between near-pristine and managed forests is not as clear. While accurate wall-to-wall dead wood inventory is not available, we recommend using DWP method together with other spatial datasets when assessing biodiversity values of forests.

Rocky pine forests in the High Coast Region in Sweden: structure, dynamics and history

Almost all forests in Sweden are managed and only a small fraction are considered natural. One exception is low productive forests where, due to their limited economical value, natural dynamics still dominate. One example is the Scots pine (Pinus sylvestris L.) forests occurring on rocky and nutrient-poor hilltops. Although these forests represent a regionally common forest type with a high degree of naturalness, their dynamics, structure and history are poorly known. We investigated the structure, human impact and fire history in eight rocky pine forests in the High Coast Area in eastern Sweden, initially identified as good representatives of this forest type. This was done by sampling and measuring tree sizes, -ages, fire-scarred trees, as well as dead wood volumes and quality along three transects at each site. The structure was diverse with a sparse layer of trees (basal area 9 m2 and 640 trees larger than 10 cm ha-1) in various sizes and ages; 13 trees ha-1 were more than 300 years old. Dead wood (DW), snags and logs in all stages of decay, was present and although the actual DW (pine) volume (4.4 m3 ha-1) and number of units (53 ha-1) was low, the DW share of total wood volume was 18% on average. Dead wood can be present for several centuries after death; we found examples of both snags and logs that had been dead more than 300 years. Frequent fires have occurred, with an average cycle of 40 years between fires. Most fires occurred between 1500-1900 and many of them (13) during the 1600s. However, fires were probably small since most fire years were only represented at one site and often only in one or a few samples. The rocky pine forests in the High Coast Area are representative of undisturbed forests with low human impact, exhibiting old-growth characteristics and are valuable habitats for organisms connected to sun-exposed DW. Management of protected rocky pine forests may well include small-scale restoration fires and the limited DW volumes should be protected.

Natural and human-related determinants of dead wood quantity and quality in a managed European lowland temperate forest

Much is known about the minimum thresholds for dead wood that would ensure the persistence of saproxylic organisms and maintain the overall biodiversity of forest ecosystems, but reaching those thresholds is still a challenge in forests where nature conservation is not the sole goal (e.g., Natura 2000 forests managed for timber). Understanding what determines the quantity and quality of dead wood in managed forests is a prerequisite for developing methods to increase its retention without decreasing a forest’s production. We surveyed the volume, number, stage of decay, and species identity of standing and lying coarse woody debris (CWD) in 183 stands in a complex of lowland Natura 2000 forests in southern Poland, and then determined the relationships between these parameters and tree stand structure, intensity of previous silviculture interventions, accessibility of terrain, and local community impact. CWD volume varied from 0.1 to 66.3 m3 ha−1 (average 6.9 m3 ha−1), which is up to several times less than the recommended thresholds. Large-sized CWD and CWD of species known to support rich communities of saproxylic organisms (e.g., Carpinus betulus) were clearly underrepresented. Wood of economically less valuable species was often left in the forest, which boosted the diversity of CWD microhabitats. CWD quantity and quality was significantly shaped by both natural and human-related factors. Among the latter, harvesting intensity and proximity to human settlements affected CWD negatively, while terrain-related difficulties (distance to roads, watercourse density) affected it positively. Surprisingly, the site accessibility effect was important even though the studied area is level and covered by a dense road network. The results suggest that cost-effective CWD management plans for Natura 2000 forests, or, more broadly, multifunctional forests, should discourage some practices accompanying timber harvesting (e.g., fragmenting of pieces of aged CWD), promote practices that positively affect CWD (e.g., not harvesting low-value timber), and set aside small areas to accelerate CWD retention. These things should be done wherever their effects are unlikely to be reversed, i.e., at sites difficult for forestry vehicles to access and away from human settlements.

Morphological traits predict host-tree specialization in wood-inhabiting fungal communities

Abstract Tree species is one of the most important determinants of wood-inhabiting fungal community composition, yet its relationship with fungal reproductive and dispersal traits remains poorly understood. We studied fungal communities (total of 657 species) inhabiting broadleaved and coniferous dead wood (total of 192 logs) in 12 semi-natural boreal forests. We utilized a trait-based hierarchical joint species distribution model to examine how the relationship between dead wood quality and species occurrence correlates with reproductive and dispersal morphological traits. Broadleaved trees had higher species richness than conifers, due to discomycetoids and pyrenomycetoids specializing in them. Resupinate and pileate species were generally specialized in coniferous dead wood. Fungi inhabiting broadleaved trees had larger and more elongated spores than fungi in conifers. Spore size was larger and spore shape more spherical in species occupying large dead wood units. These results indicate the selective effect of dead wood quality, visible not only in species diversity, but also in reproductive and dispersal traits.

Combining tree species and decay stages to increase invertebrate diversity in dead wood

Dead wood availability and the variability in dead wood quality, i.e. tree species and decay stages, are often low in managed forests, which negatively affects biodiversity of invertebrate species. Leaving more (coarse) dead wood can increase invertebrate richness, but it remains unclear how many and which combinations of tree taxa and decay stages are required to optimize niche heterogeneity in managed forests. We investigated the diversity of the main arthropod groups associated with dead wood, i.e. millipedes, centipedes, isopods and beetles, through the first four years of decomposition of logs of twenty common temperate tree species placed in the “common garden” experiment LOGLIFE. We hypothesized that (1) invertebrate richness for combinations of a given number of tree species would be promoted by mixing both tree species and decay period and that (2) invertebrate richness increases up to a saturation point with more tree species at different decay stages added. We also hypothesized that (3) an increase in phylogenetic distance among the tree species in combinations would promote their overall invertebrate diversity. We found that the better combinations, in terms of invertebrate richness, after one and two years of decay, but not after four years, consisted of a mix of gymnosperms and angiosperms, indicating that variation in tree species is especially important during the initial decomposition period. The best combinations in terms of invertebrate richness consisted of at least one tree species from each decay period, indicating that also variation in the decay stage of the tree is important to promote invertebrate diversity. We observed that at least four wood types were required to approach the 95% saturation point for species richness. The third hypothesis, that dissimilarity in phylogenetic position could be a predictive tool for increasing invertebrate richness in combinations of tree species, was not supported by our results. Thus, in order to maintain diversity of dead wood invertebrates in forests we recommend not only to provide richness in tree species, but also to plant particular combinations of trees (preferably angiosperm-gymnosperm combinations) that differ in the invertebrate communities they typically host and to temporally spread the logging of trees. This way the logging residues cover different resources and habitats at each moment in time, which is likely to result in a large diversity of dead wood invertebrates.

Application of next-generation sequencing technologies to conservation of wood-inhabiting fungi.

Next-generation sequencing (NGS) has significantly increased knowledge of microbial communities and their distribution. However, it is still not common to apply NGS technology to microbial conservation. We sought to use NGS technologies to evaluate conservation strategies for wood-inhabiting fungi. Evaluating a deadwood experiment 3 years after it was established, we specifically examined which tree species combinations promoted the highest richness of wood-inhabiting fungi. Deadwood enrichment was an effective strategy and logs of 6 tree species, either those with the highest wood-inhabiting fungal α and γ diversity or those with the highest β diversity, maintained >1,000 operational taxonomic units (OTUs) spread over a wide range of taxonomic groups. In comparison, a conservation strategy based only on the results of sporocarp surveys yielded 591 OTUs. This result highlights the need to use NGS approaches to inform microbial conservation strategies. We also determined that 5 tree species with the highest saproxylic beetle γ diversity simultaneously conserved wood-inhabiting fungi. Apart from deadwood volume, we suggest data on deadwood quality and species also be included as indicators, especially for wood-inhabiting fungal diversity, and incorporated quickly in forest assessment and monitoring systems in Central Europe.

Remotely Sensed Single Tree Data Enable the Determination of Habitat Thresholds for the Three-Toed Woodpecker (Picoides tridactylus)

Forest biodiversity conservation requires precise, area-wide information on the abundance and distribution of key habitat structures at multiple spatial scales. We combined airborne laser scanning (ALS) data with color-infrared (CIR) aerial imagery for identifying individual tree characteristics and quantifying multi-scale habitat requirements using the example of the three-toed woodpecker (Picoides tridactylus) (TTW) in the Bavarian Forest National Park (Germany). This bird, a keystone species of boreal and mountainous forests, is highly reliant on bark beetles dwelling in dead or dying trees. While previous studies showed a positive relationship between the TTW presence and the amount of deadwood as a limiting resource, we hypothesized a unimodal response with a negative effect of very high deadwood amounts and tested for effects of substrate quality. Based on 104 woodpecker presence or absence locations, habitat selection was modelled at four spatial scales reflecting different woodpecker home range sizes. The abundance of standing dead trees was the most important predictor, with an increase in the probability of TTW occurrence up to a threshold of 44–50 dead trees per hectare, followed by a decrease in the probability of occurrence. A positive relationship with the deadwood crown size indicated the importance of fresh deadwood. Remote sensing data allowed both an area-wide prediction of species occurrence and the derivation of ecological threshold values for deadwood quality and quantity for more informed conservation management.

A native long horned beetle promotes the saproxylic diversity in exotic plantations of Monterrey pine

Native saproxylic (deadwood dependent) beetle species living in exotic forest plantations may provide environmental services for forestry companies, but their sensitivity to forest management makes them difficult to conserve. Here, we used Structural Equation Models (SEM) to assess the role of the endemic beetle Acanthinodera cumingii in native forest and exotic pine plantations as an ecosystem engineer that improves the quality of deadwood for saproxylic beetles. Deadwood quality in native forest and pine plantations was accounted for by A. cumingii density and deadwood decay stage. In native forest, diversity of predators and fungivores responded positively to deadwood quality, while in the pine plantations the diversity of all functional groups, with exception of detritivores, was positively affected by deadwood quality. In addition, all saproxylic functional groups were less diverse in stumps than in logs. These findings suggest that A. cumingii larvae contribute to make more diverse the assemblages of saproxylic beetles in deadwood. We suggest that sustainable management of pine plantations based on the role of A. cumingii as an ecosystem engineer and biodiversity indicator must necessarily consider forest practices intended to mimic the native forest conditions that regulate the deadwood decay dynamics.

Response of saproxylic insect communities to logging history, tree species, stage of decay, and wood posture in the central Nearctic boreal forest

Saproxylic insect assemblages are essential functional components of forest ecosystems that can be affected by forest management. We used a split-plot ANOVA design to analyze differences in selected saproxylic insects (all arthropod orders and dipteran and parasitic hymenopteran families) emerging from dead wood of sites with different logging histories (horse-logged, mechanically-logged and unlogged), tree species (Populus and Picea), stage of decay (early- and late-decay stages) and posture (standing and downed logs) in the boreal forest of central Canada. No clear effects of logging history were seen for the studied taxa; however, interaction between logging history and other dead wood features was apparent. Cecidomyiidae consistently emerged more from Populus than from Picea dead wood. Most of the studied saproxylic families were more abundant in late-decay than in early-decay wood. Dipterans of the Cecidomyiidae, Ceratopogonidae, Empididae, Mycetophilidae and Sciaridae families, and hymenopterans of the Diapriidae and Ichneumonidae families were significantly more abundant in downed than in standing dead wood. In contrast, Mymaridae was most abundant in standing dead wood. Our study provides evidence that some insects at high taxonomic levels respond differently to dead wood quality, and this could inform future management strategies in the boreal forest for the conservation of saproxylic fauna and their ecological functions.

Community fingerprinting reveals increasing wood-inhabiting fungal diversity in unmanaged Mediterranean forests

Abstract Wood-inhabiting fungi are major decomposers of organic matter in forest systems, playing a crucial role for the maintenance of critical ecosystem processes. Despite their importance, very few studies have investigated wood-inhabiting fungi with biomolecular techniques, especially in Southern Europe. We studied deadwood quality along with stand structural attributes and local ecological parameters to disentangle the relationships between forest habitat characteristics and fungal community structure. Wood samples were collected from 72 lying dead logs in four forest reserves located along a latitudinal transect on the Italian Peninsula. The sites differed in tree species composition, management history and successional stage. The fungal community was investigated through fingerprinting analysis while physical properties of deadwood logs and structural attributes of the stands were assessed in the field. In addition, lignin, carbon and nitrogen content were analyzed for each sampled log. Our results indicate that the combination of structural and morphological aspects of the study areas played a great role in differentiating the fungal communities across these unmanaged forests. Among the wood chemical characteristics, only lignin content significantly affected the overall community structure, suggesting a role of decay stage and tree species in selecting specific fungal taxa. Climatic factors were found to be important only for fungal species diversity and was positively influenced by mean annual precipitation and negatively related to temperature annual range. Nevertheless, a mixed effect model showed a greater impact of living tree species richness in predicting fungal diversity within logs. Our findings suggest that decomposer communities respond to environmental changes at different spatial scales and that the structural and ecological heterogeneity of forest systems subjected to natural dynamics for a longer period support a more diverse fungal community.

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.