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Decomposition of wood is an important component of global carbon cycling. Most wood decomposition models are based on tree characteristics and environmental conditions; however, they do not include community dynamics of fungi that are the major wood decomposers. We examined the factors explaining variation in sapwood decay in oak tree stumps two and five years after cutting. Wood moisture content was significantly correlated with sapwood decay in younger stumps, whereas ITS-based composition and species richness of the fungal community were the best predictors for mass loss in the older stumps. Co-occurrence analysis showed that, in freshly cut trees and in younger stumps, fungal communities were nonrandomly structured, whereas fungal communities in old stumps could not be separated from a randomly assembled community. These results indicate that the most important factors explaining variation in wood decay rates can change over time and that the strength of competitive interactions between fungi in decaying tree stumps may level off with increased wood decay. Our field analysis further suggests that ascomycetes may have a prominent role in wood decay, but their wood-degrading abilities need to be further tested under controlled conditions. The next challenging step will be to integrate fungal community assembly processes in wood decay models to improve carbon sequestration estimates of forests. [ABSTRACT FROM AUTHOR]

Owing to previous methodological limitations, knowledge about the fine-scale distribution of fungal mycelia in decaying logs is limited. We investigated fungal communities in decaying Norway spruce logs at various spatial scales at two environmentally different locations in Sweden. On the basis of 454 pyrosequencing of the ITS2 region of rDNA, 1914 operational taxonomic units ( OTUs) were detected in 353 samples. The communities differed significantly among logs, but the physical distance between logs was not found to have a significant effect on whether fungal communities had any resemblance to each other. Within a log, samples that were closer together generally had communities that showed more resemblance to each other than those that were further apart. OTUs characteristic for particular positions on the logs could be identified. In general, these OTUs did not overlap with the most abundant OTUs, and their ecological role was often unknown. Only a few OTUs were detected in the majority of logs, whereas numerous OTUs were rare and present in only one or a few logs. Wood-decaying Basidiomycetes were often represented by higher sequence reads in individual logs than Ascomycete OTUs, suggesting that Basidiomycete mycelia spread out more rapidly when established. OTU richness tended to increase with the decay stage of the sample; however, the known wood decayers were most abundant in less-decomposed samples. The fungi identified in the logs represented different ecological strategies. Our findings differ from previously published sporocarp studies, indicating that the highly abundant fruiting species may respond to environment in different ways than the rest of the fungal community. [ABSTRACT FROM AUTHOR]