Experimentally manipulating forest structure to mimic management strategies: effects on deadwood fungal diversity and related ecosystem processes

Understanding the relationships between forest management, biodiversity, and ecosystem processes is necessary for achieving multifunctionality. Deadwood fungi are extremely diverse and important for carbon turnover in forests. However, how forest structure, resulting from management, affects deadwood fungal diversity and decomposition is not well known. We experimentally tested the effects of microclimate (via canopy cover) and deadwood enrichment (snags, logs, tree crowns, and habitat trees) on fungal diversity. Further, we assessed the effects of the treatments and fungal diversity on wood mass loss. We characterized the fungal communities of Fagus sylvatica (European beech) and Pinus sylvestris (Scots pine) deadwood via metabarcoding and measured wood mass loss after 3 years. We found that the host tree species was more important than canopy cover or deadwood enrichment for fungal alpha and beta diversity. Fungal alpha diversity of beech was mainly related to canopy cover; diversity of beech was higher under closed canopies. While alpha diversity of pine was related only to deadwood enrichment as diversity increased where habitat trees and crowns remained. Furthermore, while mass loss of beech was significantly higher in patches where trees were removed and patches where crowns remained, pine mass loss was neither affected by canopy cover nor deadwood enrichment. Host tree diversity is more important than environmental variability as a determinant of fungal diversity, underpinning the importance of maintaining diverse hosts in forests. However, contrasting diversity and decomposition effects between beech and pine suggest the need for forest management strategies tailored to tree species to maintain fungal diversity and ecosystem processes.