Effects of plant diversity and soil properties on soil fungal community structure with secondary succession in the Pinus yunnanensis forest

Forest secondary succession alters plant diversity and soil properties in the forest ecosystems; however, effects of this process on the soil fungal community structure are poorly understood. We used Illumina high-throughput sequencing to identify soil fungal community during forest secondary succession (including 30-, 45-, 60-, and 80-year-old stands) in the Pinus yunnanensis forest. The aims were to explore how plant diversity and soil properties drive soil fungal community structure and elucidate the role of fungal guilds in integrating the linkages of plant diversity and soil properties with forest secondary succession. Our study found that forest secondary succession changed woody species composition, richness, and soil properties, furthermore, this also affected significantly soil fungal diversity, community composition, and the abundances of the different functional guilds along the forest secondary succession. Soil fungal diversity initially increased up to the 60-year-old stand, and then decreased with forest secondary succession. The main phyla included Agaricomycetes, Leotiomycetes, Mortierellomycetes, and Eurotiomycetes, and indicator phyla varied differently with forest secondary succession. Soil fungal community could be clearly divided into the four successional stages. Forest secondary succession affected significantly soil fungal diversity via altering woody species richness and soil properties. Mycorrhizal, saprotrophic, and endophytic fungi interacted differently with forest secondary succession. Ectomycorrhizal fungi (ECM) played a vital role in driving forest secondary succession, and greater ECM fungal abundance could drive the forest secondary succession process through changes in the ECM plant composition. ECM plant community composition displayed different effects on ECM fungal abundance. As a result, ECM fungal abundance increased with a higher abundance of Castanopsis orthacantha, and decreased with a higher abundance of P. yunnanensis. Ericoid mycorrhizal fungal abundance reached its maximum in the 45-year-old stand and then decreased, which could provide valuable information for understory restoration. Undefined saprotrophic fungal abundance decreased with increasing forest secondary succession, accompanied by an increase of ECM fungal abundance, while endophytic fungi increased with forest secondary succession. Our findings suggested that plant-fungal symbionts and environmental selection posed an important constraint in assembly of soil fungal community and functional guild abundances. Altogether, these results provided new insights for predicting shifts in plant and soil fungal community strategies with the forest secondary succession in the P. yunnanensis forest.