Characteristics of culturable bacteria diversity among different permafrost types in the upstream regions of the Shule River basin,Qinghai-Tibet Plateau
Owing to climate change and human activities,significant degradation of permafrost has happened in the upstream regions of the Shule River Basin,such as the increasing depth of the active layer and vegetation degradation. However,little is known about the consequent effects of permafrost degradation to the soil microbes. In this study,we analyzed the culturable bacterial diversity of 12 permafrost-affected soil samples from four principal permafrost types,sub-stable permafrost (SSP) ,transition permafrost (TP) ,unstable permafrost (UP) and extremely unstable permafrost (EUP) in different seasons,to investigate the effects of soil properties on bacterial community structure during the process of permafrost degradation. The results showed that the genera Arthrobacter and Micrococcus were the dominant bacteria in the upstream region of the Shule River. The genus Arthrobacter comprised 15. 6% ~ 50. 1% and the genus Micrococcus comprised 7. 5% ~ 48. 5% of the total culturable bacteria,and these percentages decreased and increased during the process of permafrost degradation, respectively. Based on 16S rDNA gene sequences and the phylogenetic tree,the culturable bacteria in the study area belonged to 27genera,and fell into five phylogenetic groups: alpha-Proteobacteria,gamma-Proteobacteria,Actinobacteria, Firmicutes and Bacteroides,among which Actinobacteria was the dominate phylum. Such a culturable bacterial community structure was similar with previous studies of permafrost ecosystems. Bacterial diversity characteristics were different among different permafrost types,these results indicated that there existed huge environmental heterogeneity between different permafrost during the process of reverse vegetation succession along with permafrost degradation,and this heterogeneity has further affected the species diversity. Besides,correlation analysis showed that soil moisture,soil total nitrogen and organic carbon were important factors that affecting the culturable bacterial diversity. Hence,we can conclude that permafrost degradation,caused by global warming, affects soil properties and consequently drives changes in the soil bacterial diversity. The results provide a data base for the comprehensive evaluation of the ecological environment of different types of permafrost in Qinghai-Tibet Plateau.