Changes in nitrogen and phosphorus availability driven by secondary succession in temperate forests shape soil fungal communities and function

Soil fungal community plays an important role in forest ecosystems, and
forest secondary succession is a crucial driver of soil fungal community.
However, the driving factors of fungal community and function during
temperate forest succession and their potential impact on succession
processes are poorly understood. In this study, we investigated the
dynamics of the soil fungal community in three temperate forest secondary
successional stages (shrublands, coniferous forests, and deciduous
broadleaf forests) using high-throughput DNA sequencing coupled with
functional prediction via the FUNGuild database. We found that fungal
community richness, α-diversity, and evenness decreased significantly
during the succession process. Soil available phosphorus and nitrate
nitrogen decreased significantly after initial succession occurred, and
redundancy analysis showed that both were significant predictors of soil
fungal community structure. Among functional groups, fungal saprotrophs as
well as pathotrophs represented by plant pathogens were significantly
enriched in the early-successional stage, while fungal symbiotrophs
represented by ectomycorrhiza were significantly increased in the
late-successional stage. The abundance of both saprotroph and pathotroph
fungal guilds was positively correlated with soil nitrate nitrogen and
available phosphorus content. Ectomycorrhizal fungi were negatively
correlated with nitrate nitrogen and available phosphorus content and
positively correlated with ammonium nitrogen content. These results
indicated that the dynamics of fungal community and function reflected the
changes in nitrogen and phosphorus availability caused by the secondary
succession of temperate forests. The fungal plant pathogen accumulated in
the early-successional stage and ectomycorrhizal fungi accumulated in the
late-successional stage may have a potential role in promoting forest
succession. These findings contribute to a better understanding of the
response of soil fungal communities to the secondary forest succession
process and highlight the importance of fungal communities during
temperate forest succession.