施肥对土壤丛枝菌根真菌群落的影响

o elucidate the underlying mechnisms of how fertilization affects the arbuscular mycorrhizal (AM) fungal community in soil, the AM fungal communities in an 8 yr of nitrogen and phosphorus gradient fertilization field were investigated. A total of 37 AM fungal phylotypes was identified in 25 soil samples, of which 17 phylotypes belonged to the genus Glomus. Fertilization significantly reduced the phylotype richness of AM fungi, especially the highest level of fertilizer input caused the phylotype richness within the genus Glomus to decline by 66%, but significantly increased AM fungal genus richness. Across the fertilization gradient, the relative abundance of Glomus declined from 81% to 14%, whereas the relative abundance of Diversispora increased from 5% to 43%. Both the species and phylogenetic compositions of AM fungal communities varied among treatments, and both were correlated significantly with soil available P and the abundance of Elymus nutans (all P < 0.001). AM fungal communities were phylogenetically clustered in unfertilized soil, random in low fertilizer treatment and overdispersed in high fertilizer treatments, indicating that the primary ecological process determining AM fungal communities shifted from environmental filtering to stochastic process and finally to competitive exclusion across the fertilization gradient.