Dominant plant species and soil properties drive differential responses of fungal communities and functions in the soils and roots during secondary forest succession in the subalpine region

In this study, we provide fungal community structure analysis of three contrasting sites in secondary succession, and try to identify variables that shape fungal community composition. Soil and roots were sampled from three sites representing a secondary succession from grassland, to shrubland to forest. We analyzed the fungal community and potential ecological functions based on high-throughput sequencing and the FUNGuild database. Fungal alpha-diversity in the nonrhizosphere and bulk soils of the secondary forest was significantly higher than that in the grassland, while the opposite result was observed in roots, and no significant difference was found in fungal alpha-diversity in the rhizosphere soil. Fungal fl-diversity in the soils and roots varied significantly with succession. FUNGuild data show that the relative abundance of arbuscular mycorrhizal (AM) fungi and dung saprotroph decreased with succession; ectomycorrhizal (ECM) fungi, ericoid mycorrhizal and fungal parasite increased with succession; undefined saprotrophs and plant pathogens showed no significant difference during succession. Total phosphorus, available phosphorus and soil nitrogen: phosphorus ratio were the main factors determining fungal fl-diversity and fungal functional guilds. Interestingly, the roots of the dominant plants at three succession stages enriched plant pathogens Gibberella, Exserohilum and Venturia, respectively. In conclusion, our result revealed differential change trends in fungal alpha-diversity and fungal fl-diversity in the soils and roots among three succession stages. Moreover, the fungal functional guilds (i.e., ECM, AM, plant pathogen) also showed significant changes during succession. These results could enhance understanding of the mechanism of secondary succession in the subalpine region.