During decomposition of organic matter, microbial communities may follow different successional trajectories depending on the initial environment and colonizers. The timing and order of the assembly history can lead to divergent communities through priority effects. We explored how assembly history and substrate quality affected fungal dead wood communities and decomposition, 1.5 and 4.5 years after tree felling. In addition, we investigated the effect of invertebrate exclusion during the first two summers. For aspen (Populus tremula) logs, we measured initial bark and wood resource quality, and surveyed the fungal communities by DNA metabarcoding at different time points during succession. We found that a gradient in fungal community composition was related to resource quality and we discuss how this may reflect tolerance-dominance trade-offs in fungal life history strategies. As with previous studies, the initial amount of bark tannins was negatively correlated with wood decomposition rate over 4.5 years. The latent fungal community explained variation in community composition after 1.5, but not after 4.5 years, of succession. Although the assembly history of latent fungi may cause alternate trajectories in successional communities, our results indicate that the communities may easily converge with the arrival of secondary colonizers. We also identified a strong invertebrate-induced priority effect of fungal communities, even after 4.5 years of succession, thereby adding crucial knowledge to the importance of invertebrates in affecting fungal community development. By measuring and manipulating aspects of assembly history and resource quality that have rarely been studied, we expand our understanding of the complexity of fungal community dynamics.

Woodchips from aspen logs at three time intervals: fresh wood, after 1.5 years and after 4.5 years.

Analysed for DNA with a modified CTAB procedure, amplified with uniquely tagged primers of the ITS2 region, sequenced with Illumina Miseq.

Bioinformatics with CUTADAPT, DADA2, ITSx, VSEARCH clustering and LULU post-curation.

Taxonomic annotations from UNITE, functional guilds from FUNGUILD.

biorxiv preprint version of manuscript: https://www.biorxiv.org/content/10.1101/2021.12.01.470726v1