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Enhanced nitrogen (N) deposition due to combustion of fossil fuels and agricultural fertilization is a global phenomenon which has severely altered carbon (C) and N cycling in temperate forest ecosystems in the northern hemisphere. Although deadwood holds a substantial amount of C in forest ecosystems and thus plays a crucial role in nutrient cycling, the effect of increased N deposition on microbial processes and communities, wood chemical traits and deadwood mass loss remains unclear. Here, we simulated high N deposition rates by adding reactive N in form of ammonium-nitrate (40 kg N ha−1 yr−1) to deadwood of 13 temperate tree species over nine years in a field experiment in Germany. Non-treated deadwood from the same logs served as control with background N deposition. Our results show that chronically elevated N levels alters deadwood mass loss alongside respiration, enzymatic activities and wood chemistry depending on tree clade and species. In gymnosperm deadwood, elevated N increased mass loss by +38 %, respiration by +37 % and increased laccase activity 12-fold alongside increases of white-rot fungal abundance +89 % (p = 0.03). Furthermore, we observed marginally significant (p = 0.06) shifts of bacterial communities in gymnosperm deadwood. In angiosperm deadwood, we did not detect consistent effects on mass loss, physico-chemical properties, extracellular enzymatic activity or changes in microbial communities except for changes in abundance of 10 fungal OTUs in seven tree species and 28 bacterial OTUs in 10 tree species. We conclude that N deposition alters decomposition processes exclusively in N limited gymnosperm deadwood in the long term by enhancing fungal activity as expressed by increases in respiration rate and extracellular enzyme activity with minor shifts in decomposing microbial communities. By contrast, deadwood of angiosperm tree species had higher N concentrations and mass loss as well as community composition did not respond to N addition.

Forestry in Europe changed the tree species composition and reduced dead-wood amount and heterogeneity, and therefore negatively affected saproxylic diversity. Efficient conservation requires knowledge about the importance of the relevant diversity drivers across taxa. We examined the relative importance of space vs. host for saproxylic diversity at a spatial extend of 600 km in Germany. Further, we disentangled effects of among regions, forest stands, host clades, and tree species on saproxylic diversity. This allows inferences for spatial- and host tree-related conservation strategies. Beetle, fungal sporocarp, molecular-derived fungal, and bacterial communities were studied in a large nested dead-wood experiment comprising 11 tree species. We used multiplicative diversity partitioning to assess the diversity of rare, typical, and dominant species. The beta-diversity of beetles and fungal sporocarps was equally explained by space and host, but that of molecular fungi and bacteria mainly by the host. Across taxa, beta-diversity was higher among forest stands than among regions. However, for beetles and fungal sporocarps, differences among regions were also important. Host tree clade and host tree species were important for beetle and host clade for fungal sporocarp beta-diversity. Host tree species was more important than host clade for the beta-diversity of molecular fungi and bacteria. The divergent response of different taxa to space and host calls into question the use of a simple spatially-centered or host-centered strategy. Instead, a high dead-wood tree species diversity on a broad spatial coverage at the national scale in temperate European forests is necessary to maintain rare and abundant species.

Deadwood provides an important carbon source in forests and wooded ecosystems and, accordingly, forest management strategies discuss the enrichment of deadwood amount and diversity by different tree species. To investigate the decomposition processes of enriched deadwood, we simultaneously placed 3,669 size-standardized and gamma sterilized wood specimens of 13 tree species (Populus tremula, Tilia cordata, Prunus avium, Betula pendula, Carpinus betulus, Fraxinus excelsior, Quercus robur, Fagus sylvatica, Acer platanoides, Larix decidua, Pinus sylvestris, Picea abies, and Pseudotsuga menziesii) at a total of 300 forest and grassland plots in three regions in Germany covering large gradients of management intensity and environmental conditions. After 1 year, mass loss was calculated and its relationship with wood traits and environmental conditions was assessed to determine the most important factors. Mass loss was overall higher in forest compared to grassland habitats, with wood traits as the most important driver, followed by region and environmental factors related to microclimate. However, management intensity was less relevant to explain the mass loss in both habitats. Our results suggest that decomposition of enriched deadwood, even after removal of endophytes, is influenced by the same drivers (positively by moisture and abundance of macronutrients, negatively by lignin and phenol concentration) as naturally occurring wood. Furthermore, due to the immense and standardized experimental setting, our study contributes to a better understanding of the important drivers of mass loss in different tree species and thus provides the basis for predictions of the carbon cycle in a changing world.

The home-field advantage (HFA) hypothesis has been used intensively to study leaf litter decomposition in various ecosystems. However, the HFA in woody substrates is still unexplored. Here, we reanalyzed and integrated existing datasets on various groups of microorganisms collected from natural deadwood of two temperate trees, Fagus sylvatica and Picea abies, from forests in which one or other of these species dominates but where both are present. Our aims were (i) to test the HFA hypothesis on wood decomposition rates of these two temperate tree species, and (ii) to investigate if HFA hypothesis can be explained by diversity and community composition of bacteria and in detail N-fixing bacteria (as determined by molecular 16S rRNA and nifH gene amplification) and fungi (as determined by molecular ITS rRNA amplification and sporocarp surveys). Our results showed that wood decomposition rates were accelerated at “home” versus “away” by 38.19% ± 20.04% (mean ± SE). We detected strong changes in fungal richness (increase 36–50%) and community composition (RANOSIM = 0.52–0.60, P < 0.05) according to HFA hypothesis. The changes of fungi were much stronger than for total bacteria and nitrogen fixing for both at richness and community composition levels. In conclusion, our results support the HFA hypothesis in deadwood: decomposition rate is accelerated at home due to specialization of fungal communities produced by the plant community above them. Furthermore, the higher richness of fungal sporocarps and nitrogen-fixing bacteria (nifH) may stimulate or at least stabilize wood decomposition rates at “home” versus “away.”

Trade-offs and synergies in the supply of forest ecosystem services are common but the drivers of these relationships are poorly understood. To guide management that seeks to promote multiple services, we investigated the relationships between 12 stand-level forest attributes, including structure, composition, heterogeneity and plant diversity, plus 4 environmental factors, and proxies for 14 ecosystem services in 150 temperate forest plots. Our results show that forest attributes are the best predictors of most ecosystem services and are also good predictors of several synergies and trade-offs between services. Environmental factors also play an important role, mostly in combination with forest attributes. Our study suggests that managing forests to increase structural heterogeneity, maintain large trees, and canopy gaps would promote the supply of multiple ecosystem services. These results highlight the potential for forest management to encourage multifunctional forests and suggest that a coordinated landscape-scale strategy could help to mitigate trade-offs in human-dominated landscapes.

Despite the important role of wood-inhabiting fungi (WIF) in deadwood decomposition, our knowledge of the factors shaping the dynamics of their species richness and community composition is scarce. This is due to limitations regarding the resolution of classical methods used for characterizing WIF communities and to a lack of well-replicated long-term experiments with sufficient numbers of tree species. Here, we used a large scale experiment with logs of 11 tree species at an early stage of decomposition, distributed across three regions of Germany, to identify the factors shaping WIF community composition and Operational Taxonomic Unit (OTU) richness using next generation sequencing. We found that tree species identity was the most significant factor, corresponding to (P < 0.001) and explaining 10% (representing 48% of the explainable variance) of the overall WIF community composition. The next important group of variables were wood-physicochemical properties, of which wood pH was the only factor that consistently corresponded to WIF community composition. For overall WIF richness patterns, we found that approximately 20% of the total variance was explained by wood N content, location, tree species identity and wood density. It is noteworthy that the importance of determinants of WIF community composition and richness appeared to depend greatly on tree species group (broadleaved vs. coniferous) and it differed between the fungal phyla Ascomycota and Basidiomycota.

Nitrogen deposition can strongly affect biodiversity, but its specific effects on terrestrial microbial communities and their roles for ecosystem functions and processes are still unclear. Here, we investigated the impacts of N deposition on wood‐inhabiting fungi (WIF) and their related ecological functions and processes in a highly N‐limited deadwood habitat. Based on high‐throughput sequencing, enzymatic activity assay and measurements of wood decomposition rates, we show that N addition has no significant effect on the overall WIF community composition or on related ecosystem functions and processes in this habitat. Nevertheless, we detected several switches in presence/absence (gain/loss) of wood‐inhabiting fungal OTUs due to the effect of N addition. The responses of WIF differed from previous studies carried out with fungi living in soil and leaf‐litter, which represent less N‐limited fungal habitats. Our results suggest that adaptation at different levels of organization and functional redundancy may explain this buffered response and the resistant microbial‐mediated ecosystem function and processes against N deposition in highly N‐limited habitats.

Mit Ausnahme der Diskussionen zu den Auswirkungen zu hoher Schalenwilddichten wird in der Forstwirtschaft kaum ein Thema derzeit so leidenschaftlich diskutiert wie die Auswirkungen der Waldbewirtschaftung auf die Biodiversität [2, 3, 4]. Hierbei stehen Buchenwälder aufgrund ihres in Mitteleuropa gelegenen Verbreitungsschwerpunkts im Vordergrund der Diskussionen. Viele dieser Debatten münden letztlich in der Frage, ob und wenn ja wie viel der bislang bewirtschafteten Waldfl äche über die bisher vorhandenen Naturwaldfl ächen hinaus aus der Nutzung genommen werden sollte [5].

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 6.5 years 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.

In forest ecosystems, deadwood is an important component that provides habitat and contributes to nutrient cycles, as well as to carbon and water storage. The change of wood constituents, nutrients and microbial species richness in the field over the whole time of decomposition has only rarely been studied, in particular not in relation to oxidative enzyme activities (mediating lignin degradation) and different forest management regimes.To describe wood decomposition, we selected coarse woody debris (CWD) in form of 197 logs of Fagus sylvatica, Picea abies and Pinus sylvestris in forests with different management regimes across three regions in Germany. They were sampled and analyzed for wood density, water content, wood constituents (Klason and acid-soluble lignin, organic extractives, water-soluble lignin fragments), carbon, nitrogen and metals (Al, Ca, Cu, K, Mg, Mn and Zn). Furthermore, the activities of oxidative enzymes like laccase, manganese peroxidase, and general peroxidase were measured. Since filamentous fungi (Basidiomycota, Ascomycota) are the major biological agents of wood decomposition, fungal species richness based on sporocarps and molecular fingerprints was recorded.Higher forest management intensity had a negative effect on deadwood volume and in consequence on fungal species richness (sporocarps), but hardly to other analyzed variables. Furthermore, there were significant differences between the tree species for the concentrations of wood constituents and most nutrients as well as the activities of oxidative enzymes, although their course during decomposition was mostly similar among the tree species. We found that molecular species richness increased with the period of decomposition in contrast to the number of fruiting species, which was highest in the intermediate stage of decomposition. Both types of species richness increased with increasing volume of the CWD logs. Regarding the entire period of decomposition, white-rot fungi (WRF), based

Wood-inhabiting fungi are major agents of wood decomposition. However, it is unclear which factors determine their distribution and enzyme production. Many studies that have addressed this issue suffer from a lack of geographic extent. Here, we investigate the fungal community structure of 117 Fagus sylvatica logs in relation to wood physico-chemical properties and secreted ligninolytic enzymes, across three distinct geographical regions of Germany. Our results revealed that fungal community structure was similar across different regions, but was nevertheless variable in all regions. The relationships between fungal community structure, wood physico-chemical properties and enzyme activities were not consistent across different regions. However, we identified that the wood physico-chemical properties (i.e. decay class, remaining mass, density, extractives, total lignin and pH) were the most important factors associated with the fungal community structure in all three regions. In contrast, the wood physico-chemical properties and the fungal community structure did not sufficiently explain variation in the detected enzymatic activities. Thus, we assume that interspecific interactions and recently described priority effects play more important roles in the production of lignin modifying enzymes.

Lignin and its degradation, particularly in forest ecosystems, play a major role in the global carbon cycle. Filamentous fungi equipped with extracellular oxidoreductases (oxidative enzymes), i.e., laccase, manganese-dependent peroxidases and several other peroxidases, are the key players in the bioconversion of lignin. In particular, for coarse woody debris (CWD), this process is poorly understood and the activities of laccase and peroxidases have never been studied on a large field scale. We investigated the activities of these enzymes in 701 samples of Fagus sylvatica, Picea abies and Pinus sylvestris CWD across three regions in Germany and analyzed their dependence on pH, water content, wood density, total lignin, organic extractives, metals, water-soluble lignin fragments and fungal species richness. Respective enzyme activities were present in 79 % of all samples, and the activities were highly variable and more frequent in F. sylvatica than in coniferous wood. Logistic regressions and correlations between enzyme activities and the variables revealed that the fungal community structure and the amount of water-soluble lignin fragments are most important determinants, and that the prevalent acidic pH in CWD is suitable to facilitate laccase and manganese peroxidase activities. Concentrations of metals (manganese, copper, iron) were sufficient to ensure synthesis and functioning of relevant enzymes. Based on this large field study, we conclude that laccase and peroxidases in CWD are highly relevant for lignin degradation, but the variable pattern of their secretion is the result of a complex array of wood parameters and the fungal community structure, which could only partly be resolved.

Fungi play vital roles in the decomposition of deadwood due to their secretion of various enzymes that break down plant cell-wall complexes. The compositions of wood-inhabiting fungal (WIF) communities change over the course of the decomposition process as the remaining mass of wood decreases and both abiotic and biotic conditions of the wood significantly change. It is currently not resolved which substrate-related factors govern these changes in WIF communities and whether such changes influence the deadwood decomposition rate. Here we report a study on fungal richness and community structure in deadwood of Norway spruce and European beech in temperate forest ecosystems using 454 pyrosequencing. Our aims were to disentangle the factors that correspond to WIF community composition and to investigate the links between fungal richness, taxonomically-resolved fungal identity, and microbial-mediated ecosystem functions and processes by analyzing physico-chemical wood properties, lignin-modifying enzyme activities and wood decomposition rates. Unlike fungal richness, we found significant differences in community structure between deadwood of different tree species. The composition of WIF communities was related to the physico-chemical properties of the deadwood substrates. Decomposition rates and the activities of lignin-modifying enzymes were controlled by the succession of the fungal communities and competition scenarios rather than fungal OTU richness. Our results provide further insights into links between fungal community structure and microbial-mediated ecosystem functions and processes.

Decaying wood hosts a large diversity of seldom investigated protists. Environmental sequencing offers novel insights into communities, but has rarely been applied to saproxylic protists. We investigated the diversity of bright spored wood-inhabiting Myxomycetes by environmental sequencing. Myxomycetes have a complex life cycle culminating in the formation of mainly macroscopic fruiting bodies, highly variable in shape and colour that are often found on decaying logs. Our hypothesis was that diversity of bright spored Myxomycetes would increase with decay. DNA was extracted from wood chips collected from 17 beech logs of varying decay stages from the Hainich-Dün region in Central Germany. We obtained 260 partial small subunit ribosomal RNA gene sequences of bright spore Myxomycetes that were assembled into 29 OTUs, of which 65% were less than 98% similar to those in the existing database. The OTU richness revealed by molecular analysis surpassed that of a parallel inventory of fruiting-bodies. We tested several environmental variables and identified pH, rather than decay stage, as the main structuring factor of myxomycete distribution.

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 Fagus sylvatica and Picea abies 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 Fagus sylvatica and Picea abies. 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 a woodblock experiment of Fagus sylvatica. 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.