Secondary metabolites and nutrients explain fungal community composition in aspen wood

Fungi are the main decomposers of litter and wood, driving carbon and nutrient cycles. Despite a large number of studies, fungal community composition is remarkably difficult to predict. In the present study, we explore the importance of secondary metabolites and nutrient content in wood and bark as determinants of fungal com-munity composition. We used aspen (Populus tremula) logs of similar size, from one location, and measured concentrations of carbon, nitrogen and secondary metabolites in bark and wood sampled shortly after felling. Fungal DNA was extracted from logs directly after felling and after two seasons of decomposition, and the fungal communities were assessed using DNA-metabarcoding. Concentrations of metabolites varied considerably be-tween individual trees, and we also observed significant differences within single trees. Plant metabolites and nitrogen concentrations significantly affected fungal community composition. For the overall fungal commu-nities and for wood saprotrophic fungi, the explanatory power of wood and bark metabolites was highest in logs decomposed over two seasons. In recently felled trees however, concentration of metabolites had a stronger effect on plant pathogens and endophytes. We conclude that secondary metabolites represent an overlooked, but important niche dimension for fungal communities in both functional sapwood and dead wood.

Automated summary

This study explores the importance of secondary metabolites and nutrient content in wood and bark for fungal community composition, and finds that they have significant effects on fungal communities. Secondary metabolites represent an important niche dimension for fungal communities in both functional sapwood and dead wood.