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Some forest-related studies on possible effects of climate change conclude that growth potential of European beech ( Fagus sylvatica L.) might be impaired by the predicted increase in future serious drought events during the growing season. Other recent research suggests that not only multiyear increment rates but also growth resistance and recovery of beech during, respectively, after dry years may differ between pure and mixed stands. Thus, we combined dendrochronological investigations and wood stable isotope measurements to further investigate the impact of neighborhood diversity on long-term performance, short-term drought response and soil water availability of European beech in three major geographic regions of Germany. During the last four decades, target trees whose competitive neighborhood consisted of co-occurring species exhibited a superior growth performance compared to beeches in pure stands of the same investigation area. This general pattern was also found in exceptional dry years. Although the summer droughts of 1976 and 2003 predominantly caused stronger relative growth declines if target trees were exposed to interspecific competition, with few exceptions they still formed wider annual rings than beeches growing in close-by monocultures. Within the same study region, recovery of standardized beech target tree radial growth was consistently slower in monospecific stands than in the neighborhood of other competitor species. These findings suggest an improved water availability of beech in mixtures what is in line with the results of the stable isotope analysis. Apparently, the magnitude of competitive complementarity determines the growth response of target beech trees in mixtures. Our investigation strongly suggest that the sensitivity of European beech to environmental constrains depends on neighborhood identity. Therefore, the systematic formation of mixed stands tends to be an appropriate silvicultural measure to mitigate the effects of global warming and droughts on growth patterns of Fagus sylvatica. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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-spored 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. [ABSTRACT FROM AUTHOR]