The New phytologist | 2021
Ectomycorrhizal fungal decay traits along a soil nitrogen gradient.
Abstract
The extent to which ectomycorrhizal fungi decay soil organic matter SOM has implications for accurate predictions of forest ecosystem response to climate change. The distribution of gene-traits associated with SOM decay remains poorly understood among ectomycorrhizal fungal communities. We hypothesized that soil inorganic N availability acts as an environmental filter that structures the distribution of genes associated with SOM decay and specifically, that ectomycorrhizal fungal communities occurring in inorganic N poor soils have greater SOM decay potential. To test this hypothesis, we paired amplicon and shotgun metagenomic sequencing of 60 ectomycorrhizal fungal communities associating with Quercus rubra L. along a natural soil inorganic N gradient. Ectomycorrhizal fungal communities occurring in low inorganic N soils were enriched in gene families involved in the decay of lignin, cellulose, and chitin. Ectomycorrhizal fungal community composition were the strongest driver of shifts in metagenomic estimates of fungal decay potential. Our study illuminates the identity of key ectomycorrhizal fungal taxa and gene families potentially involved in the decay of SOM, and we link rhizomorphic and medium-distance hyphal morphologies with enhanced SOM decay potential. Coupled shifts in ectomycorrhizal fungal community composition and community level decay gene frequencies are consistent with outcomes of trait-mediated community assembly processes.