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Background: Tree mycorrhizal types (arbuscular mycorrhizal fungi and ectomycorrhizal fungi) alter nutrient use traits and leaf physicochemical properties and, thus, affect leaf litter decomposition. However, little is known about how different tree mycorrhizal species affect the microbial diversity, community composition, function, and community assembly processes that govern leaf litter-dwelling microbes during leaf litter decomposition. Methods: In this study, we investigated the microbial diversity, community dynamics, and community assembly processes of nine temperate tree species using high-resolution molecular technique (Illumina sequencing), including broadleaved arbuscular mycorrhizal, broadleaved ectomycorrhizal, and coniferous ectomycorrhizal tree types, during leaf litter decomposition. Results and discussion: The leaves and needles of different tree mycorrhizal types significantly affected the microbial richness and community composition during leaf litter decomposition. Leaf litter mass loss was related to higher sequence reads of a few bacterial functional groups, particularly N-fixing bacteria. Furthermore, a link between bacterial and fungal community composition and hydrolytic and/or oxidative enzyme activity was found. The microbial communities in the leaf litter of different tree mycorrhizal types were governed by different proportions of determinism and stochasticity, which changed throughout litter decomposition. Specifically, determinism (mainly variable selection) controlling bacterial community composition increased over time. In contrast, stochasticity (mainly ecological drift) increasingly governed fungal community composition. Finally, the co-occurrence network analysis showed greater competition between bacteria and fungi in the early stages of litter decomposition and revealed a contrasting pattern between mycorrhizal types. Conclusion: Overall, we conclude that tree mycorrhizal types influence leaf litter quality, which affects microbial richness and community composition, and thus, leaf litter decomposition. [ABSTRACT FROM AUTHOR]

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." [ABSTRACT FROM AUTHOR]

• The microbial co-occurrence networks along soil depths in Mt. Oakley were analyzed. • There were contrasting patterns between soil bacterial and fungal diversity along altitudinal gradient. • Altitude was more important than soil depth for shaping soil microbial communities. • Main drivers of microbial community structure are consistent for whole and sub-network communities. • Sub-network community analysis revealed important drivers that do not capture by whole community. Soil bacterial and fungal communities with different key ecological functions play important roles in boreal forest ecosystems. Although several studies have reported on the altitudinal distribution patterns of microbes, our understanding of the characteristics of the microbial community and the core composition of the microbiome in cold-temperate montane forests is still limited. In this study, Illumina MiSeq sequencing was used to investigate the changes in soil bacterial and fungal communities in surface and subsurface soils along an altitudinal gradient (from 830 m to 1300 m) on Oakley Mountain. The diversity of the bacterial and fungal communities showed a monotonic decrease and a monotonic increase with altitude, respectively. The influence of altitude on the bacterial and fungal community composition was stronger than that of soil depth. The variations in pH and dissolved organic nitrogen content at different altitudes were the main factors influencing the bacterial and fungal community structures, respectively. There was no obvious difference between the network structures of the surface and subsurface soil fungal communities, while the network of the subsurface soil bacterial community was more complex and intricate than that of the surface soil bacterial community. The network nodes mainly belonging to Proteobacteria and Actinobacteria were the key bacterial taxa in the two soil layers. Although the main drivers of microbial community structure are consistent for whole and sub-nerwork communities, the subnetwork community analysis revealed other important drivers (i.e. soil temperature and nitrate nitrogen) that do not capture by whole community analysis. Thus, the more comprehensive picture of the important factors shaping microbial community structure can be achieved by combining whole and subnetwork community analyses. Our results demonstrated that altitude had a stronger influence on soil bacterial and fungal communities than soil depth and that bacterial and fungal communities showed divergent patterns with altitude and soil depth. [ABSTRACT FROM AUTHOR]