Effects of tree mycorrhizal types and their mixtures as well as tree diversity on soil microbial communities

Abstract

Forest soil microbial communities are key to nutrient cycling and ecosystem functioning, shaped by tree diversity and mycorrhizal associations. Using the MyDiv tree diversity experiment with AM, EcM, and mixed plots, we assessed fungal and bacterial communities in tree rooting zones via ITS2 and 16S rRNA sequencing. AM plots showed higher fungal richness than EcM or mixed plots. Fungal community dissimilarity depended on co-existing tree mycorrhizal types, while rooting zones had no effect. Deterministic processes declined from AM to EcM plots, while stochastic processes rose due to dispersal effects. Fungal subcommunities were shaped by both processes, bacterial mostly by stochasticity. Tree species influenced functional gene profiles (C, N, P), with distinct patterns across diversity gradients. Our findings underline the importance of tree-mycorrhizal diversity in structuring soil microbiomes and guiding forest management.