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Aim Fungi are drivers of wood decay in forested ecosystem, while bryophytes use dead wood as a platform for their autotrophic lifestyle. We tested the hypothesis that fungal communities on beech logs are mainly structured by substrate quality, while bryophyte communities are structured by climatic gradients. In addition, we tested whether community structure in both organism groups is altered along a gradient from nearly pristine forest to forests heavily affected by management and human disturbance in the past. Location Europe. Methods We surveyed 1207 fallen beech logs in 26 of the best‐preserved forest stands across six European countries, representing a gradient in overall naturalness of the forest landscape. Recorded species were classified into ecological guilds. Indirect ordination and variation partitioning was used to analyse the relationship between species composition and environmental variables, recorded at log or site level. Results In total, 10,367 bryophyte and 15,575 fungal records were made, representing 157 and 272 species, respectively. Fungal communities were more clearly structured by substrate quality than were bryophyte communities. In both groups a distinct turnover in species composition was evident along a longitudinal gradient from Central to Western Europe. Fungi specialized in trunk rot and specialized epixylic bryophytes were scarcely represented in Atlantic regions, and partly replaced by species belonging to less specialized guilds. Variables related to climate and forest conditions were confounded along this main geographical gradient in community composition. Main conclusions We found that bryophyte and fungal communities co‐occurring on fallen beech logs in European beech forest reserves differed in their responses to biogeographical drivers and local‐scale habitat filters. Both groups responded to major gradients in climate and forest conditions, but the loss of specialist guilds in degraded forest landscapes points to a functionally important effect of forest landscape degradation at the European continental scale.

The forest cover of the western European lowland plain has been very low for centuries. Remaining forests were intensively managed, and old-growth elements like veteran trees and coarse woody debris became virtually absent. Only over the last decades have these old-growth elements progressively redeveloped in parks, lanes and forests, and have now reached their highest level over the last 500-1000 years. Biodiversity associated with these old-growth elements makes up an important part of overall forest biodiversity. The ability of species to recolonise the newly available habitat is strongly determined by limitations in their dispersal and establishment. We analyse the current status and development of old-growth elements in Flanders (northern Belgium) and the process of recolonisation by means of specific cases, focussing on saproxylic fungi and saproxylic beetles. Our results show that 'hotspots' of secondary old growth, even isolated small patches, may have more potential for specialised biodiversity than expected, and may provide important new strongholds for recovery and recolonisation of an important share of old-growth related species.

+358-40-8204799 AbstractIntensive forest management creates habitat degradation by reducing the variation of forest stands in general, and by removing old trees and dead wood in particular. Nonintervention forest reserves are commonly believed to be the most efficient tool to counteract the negative effects on biodiversity, but actual knowledge of the conservation efficiency is limited, especially for recent reserves. The structure of ecological communities is often described with measures of nestedness, beta diversity and similarity between communities. We studied whether these measures differ among forest reserves with different management histories. For this purpose, we used a large data set of woodinhabiting fungi collected from dead beech trees in European beech-dominated forest reserves. The structure of fungal assemblages showed high beta diversity, while nestedness and similarity was low. During the decomposition process of trees beta diversity between the communities occupying different trees increased in natural, but not in previously managed sites. Effects of management and decay process on nestedness were complex. We argue that the detected differences most likely reflect historical effects 3 which have extirpated specialised species from the local species pools in managed sites, and resulted in more homogeneous communities in managed sites. It is alarming that community structure is affected the most in the latest decay stages where the decay process turns the dead wood into litter, and which is thus the interface between the wood decay and the litter-decaying ecosystem. The effects of simplified communities in late decay stages on soil biodiversity should be studied.

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