Abstract
Deadwood decomposition is relevant in nature and wood inhabiting fungi (WIF) are its main decomposers. However, climate influence on WIF community and their interactions with bacteria are poorly understood. Therefore, we set up an in-field mesocosm experiment in the Italian Alps and monitored the effect of slope exposure (north- vs. south-facing slope) on the decomposition of Picea abies wood blocks and their microbiome over two years. Unlike fungal richness and diversity, we observed compositional and functional differences in the WIF communities as a function of exposure. Wood-degrading operational taxonomic units (OTUs) such as Mycena, and mycorrhizal and endophytic OTUs were characteristic of the south-facing slope. On the north-facing one, Mucoromycota, primarily Mucor, were abundant and mixotrophic basidiomycetes with limited lignin-degrading capacities had a higher prevalence compared to the southern slope. The colder, more humid conditions and prolonged snow-coverage at north exposure likely influenced the development of the wood-degrading microbial communities. Networks between WIF and N2-fixing bacteria were composed of higher numbers of interacting microbial units and showed denser connections at the south-facing slope. The association of WIF to N2-fixing Burkholderiales and Rhizobiales could have provided additional competitive advantages, especially for early wood colonization.
Highlights
Deadwood decomposition is relevant in nature and wood inhabiting fungi (WIF) are its main decomposers
Biotic drivers affect WIF richness and diversity. These are related to the host tree species[3,13], the fungal community assembly[14,15], the interactions between WIF and saproxylic insects[16,17], and the interactions between fungal and bacterial deadwood colonizers[18,19,20,21]
The role of bacteria in decomposing wood has been underestimated despite evident mutualistic relationships between N2-fixing bacteria and WIF communities[18,22,23]
Summary
Deadwood decomposition is relevant in nature and wood inhabiting fungi (WIF) are its main decomposers. The wood decomposition rates of these two temperate tree species positively correlated with the richness of fruiting bodies and N2-fixing bacteria[23] Topographic features such as slope exposure may have important consequences on deadwood decomposition process[24] and on the underlying soil microbial communities as recently shown in a 2-year mesocosm monitoring of P. abies wood decomposition performed at the same experimental site in the Italian Alps[25,26,27,28]. A faster deadwood decomposition rate at the south-facing slope with respect to the north-facing one was related to a higher bacterial richness and a higher number of detected specialist operational taxonomic units (OTUs)[28] It is still unclear whether and how exposure affects the interactions between fungal and bacterial deadwood colonizers
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