Abstract: To clarify the variation of species composition, diversity, and functional structure of soil fungi community along alpine meadow degradation,we examined the characteristics and controlling factors of soil fungal communities in non-degraded, lightly degraded, moderately degraded, severely degraded and extremely degraded (black soil beach) alpine meadows at the Three Rivers Source Region, based on the high-throughput gene sequencing and FUNGuild functional prediction. The results showed that the dominant phyla in alpine meadow soil were Ascomycota, Basidiomycetes, and Mortierellomycota. Species composition of soil fungal community varied greatly in alpine meadow under different levels of degradation. The abundance of Cladosporium flabelliforme, Entoloma sodale, Hygrocybe conica, Inocybe sp. and Trichocladium opacum increased, while that of Gibberella tricincta and Dactylonectria macrodidyma decreased following grassland degradation. The meadow under severe degradation had higher soil fungal Chao1 index, while that under light degradation had lower Shannon index and Simpson index. The abundance of pathologic, symbiotic, and saprophytic types of fungi varied among different alpine meadows. Along with the grassland degradation, the abundance of soil symbiotic fungi decreased, while that of pathological fungi increased. The soil fungal community and functional compositions changed obviously with degradation in the alpine meadow. Plant aboveground biomass, soil water content, pH, total organic carbon, total nitrogen, ammonium nitrogen, available phosphate, total potassium and AN/AP (ratio of available nitrogen and available phosphorus) were the main driving factors for the variations in soil fungal community structure.

Key words: Three Rivers Source Region, degraded grassland, soil microorganisms, community diversity, functional structure