Effects of grassland degradation on soil fungal communities in alpine steppes of the Three-River Headwaters Region during different growth periods

Soil fungal communities play an important role in nutrient cycling in grassland ecosystems, but the effects of grassland degradation on soil fungal communities during various vegetation growth stages remain unclear. Therefore, we investigated the soil fungal diversity and community composition at the early, middle, and late plant growth periods in original and degraded alpine steppes in the Three-River Headwaters Region using high-throughput sequencing techniques, and then assessed the biotic and abiotic driving factors. The results showed that the dominant soil fungal phyla in the alpine steppe were Ascomycota and Basidiomycota, and grassland degradation significantly reduced their relative abundance. During the different growing seasons, the soil fungal community diversity was significantly different (P < 0.05), and was lower at the beginning of the growing season and higher at the end. Grassland degradation did not affect soil fungal community diversity significantly (P > 0.05), but significantly changed the soil fungal community structure during different growing seasons (P < 0.05). When compared with the original alpine steppe, soil fungal community composition variations in the degraded alpine steppe were highly correlated with the plant community, and plant biomass and soil organic matter content were the major factors affecting the soil fungal community composition (P < 0.05). In summary, grassland degradation altered soil fungal communities and enhanced their resource limitations during plant growth. Therefore, restoration strategies targeting vegetation communities will facilitate the recovery of soil fungal communities, especially in degraded alpine grasslands.