RESUMO
The soil fungal community plays an important role in forest ecosystems and is crucially influenced by forest secondary succession. However, the driving factors of fungal community and function during temperate forest succession and their potential impact on succession processes remain 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 broad-leaved 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 and 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 indicate that the dynamics of fungal community and function reflected the changes in nitrogen and phosphorus availability caused by the secondary succession in 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 secondary forest succession and highlight the importance of fungal communities during the successional process.
RESUMO
There is growing interest in understanding the role that plant-soil feedbacks (PSFs) may play in invasion resistance. However, recent studies have shown that there is great uncertainty in explaining community patterns by PSF studies regarding invasions. This uncertainty may be partly because soils used for PSF studies are usually collected from open areas rather than natural communities, thus ignoring the effects of community contexts that may specifically influence the soil feedbacks of community residents to invaders. We performed a two-phase pot experiment to study the soil feedback initiated by ten co-occurring native and exotic species to a forest invader, Phytolacca americana, and the experiments were performed in forest soil and open area soil. The context-dependent mechanisms were further explored by studying different components of PSF. The results showed that natives and exotics had positive and negative effects on P. americana in the open area soil, respectively, but both had negative effects in the forest soil. Nutrient limitation was more important for the PSF in open area soil, whereas biotic factors were likely the primary mechanisms explaining the PSF in forest soil. Additionally, the litter-mediated allelopathy of dominant Quercus acutissima caused the strongest inhibition of the invader. These results suggest that native species can effectively resist invasion by producing negative PSF depending on the community context. Evidence that exotic species promote invasion through positive PSFs was not obtained. This study provided preliminary insights into the possibility of bridging PSF studies and community patterns.
