Soil fungal composition under decomposing deadwood is largely affected by tree bark density rather than soil properties

Abstract

Deadwood is an important structural and biological component of forest ecosystems habitating for a variety of soil fungal communities. However, it is unknown how decomposition of deadwood impacts fungal communities in the soil underneath functionally different tree species in forests. This study compared the effects of the barks of seven tree species, differing in physicochemical characteristics, on soil fungal communities during the early stages of deadwood decomposition in a subtropical forest. A field experiment consisting of 3 evergreen broadleaf, 3 deciduous broadleaf and 1 coniferous tree species, was conducted for 18 months to examine the impact of deadwood decomposition on soil fungal community using real-time PCR and high-throughput sequencing. Our results demonstrated that wood decomposition led to significant declines in soil pH. Functionally distinct tree species significantly shaped the distinct soil fungal composition and abundances underneath the deadwood of both broadleaf and coniferous trees after 18 months of decomposition. The fungal ecological guilds underneath the deadwood were altered, with symbiotrophs being more prominent, and a higher proportion of pathogens were observed under certain broadleaf tree species. Out of the soil fungal ASVs detected, only 51 (3 %) were generalists, while 1053 ASVs (52 %) exhibited traits indicating potential fungal specialists. There were stronger coniferous tree species preferences in soil fungal composition, compared to broadleaf trees. The initial bark density from broadleaf and coniferous species illustrated the most obvious difference. Interestingly, tree bark density, rather than soil chemistry, was the key driver causing the fluctuations in fungal composition during deadwood decomposition. Tree species traits notably affected soil fungal community during early wood decomposition. These findings highlight the importance of considering the bark traits in understanding the dynamics of soil fungal communities and its implications for forest health and ecosystem management.