Features of Soil Cultivable Microorganism Quantity and Diversity Distribution under Different Alpine Grassland Ecosystems in Qinghai-Tibet Plateau

Three representative alpine grassland ecosystems in the Qinghai-Tibet Plateau were selected to investigate the seasonal dynamics of their soil cultivable microorganisms. The results show that the amount of soil microorganism ranges from 0.4 x 107 CFU times g super(-1) to 4.6 x 107 CFU times g super(-1) and differs significantly with season. The amount of soil microorganism is the most in May in alpine sandy grassland and alpine cold swamp grassland, while is more in July in alpine-cold meadow. Based on the 16S rDNA gene sequence and phylogenetic tree, the cultivable bacteria in present study belong to 21 genera and fall into five phylogenetic groups: alpha -Proteobacteria, beta -Proteobacteria, gamma -Proteobacteria, Actinobacteria and Firmicutes, among which Actinobacteria is the predominant one. Further analysis shows that the bacteria are characterized by a taxa-area relationship. This relationship is governed primarily by environmental heterogeneity rather than geographic distance or plant composition. Al