Study On Community Structure And Diversity Of Microorganism In Degraded Alpine Grassland Ecosystem On The Tibet Plateau

Alpine grassland of Qinghai-Tibet Plateau is the most unique grassland and the area accounts for 37.64% of the total national grasslands. This is not only a very important animal husbandry base in China, but also plays a very important role in promoting regional economic development, protecting ecological environment and maintaining ecological balance. In recent years, alpine grassland of Qinghai-Tibet Plateau was degrading seriously due to the sensibility and frangibility of the ecosystem as well as natural and man-made dual factors. If the situation continues deteriorating, Qinghai-Tibet Plateau may become the fourth dust source of China. The current research focuses on the changes of the above-ground vegetation, rodents, and soil physicochemical characteristics, which has already yielded good results. We investigated bacterial and archaeal communities recovered from four different alpine grassland environments:ND (non degraded), MD (moderately degraded), HD (heavily degraded), ED (extremely degraded) in the area of Shule River. For each sample, both bacterial and archaeal total DNA was extracted and 16S rRNA clone libraries were constructed, respectively, to analyze the structure composition and distribution characteristics of microbial community. We hope that the study could contribute to the restoration of degraded grassland and the maintenance of biodiversity on the Tibetan Plateau. The main results of this study are as follows:1. The variation and of bacterial community structure and diversity in degraded alpine grasslandAll retrieved bacterial sequences were classified into nine groups:Proteobacteria(α,β,γ,δ), Acidobacteria, Actinomycetes, Bacteroidetes, Vemicomicrobia, Gemmatimonadetes, Firmicutes, Planctmycetes and Unclassified. Proteobacteria, Acidobacteria and Actinomycetes were significantly dominant groups in four habitats.With the degradation of alpine grassland, the relative abundances of a-Proteobacteria, ^-Proteobacteria, Acidobacteria, Bacteroidetes and Planctomycetes decreased, and some had significant variation in different habitats (P<0.05); while the relative abundances of y-Proteobacteria, Actinomycetes, Gemmatimonadetes, Firmicutes increased, and also had significant variation (P<0.05). In addition, we found that the ratio of Proteobacteria and Acidobacteria declined with degradation, which is reported to have a great relationship with soil organic matter. From a diversity point of view, the Richness Index, Shannon-Weaver Index and Simpson index diminished with degradation.Through the NMDS analysis, it was found that grassland degradation changed the diversity of above-ground vegetation and soil physicochemical characteristics, most of which were the main factors to change bacteria community structure and abundance (P<0.05).2. The variation and of archeal community structure and diversity in degraded alpine grasslandThe phylogenetic analysis of archaeal 16S rRNA shows that all sequences belonged to Crenarchaeota, which were assigned to three groups:Groupl.1b, Group1.1a and Groupl.3. Group 1.1b is the dominant group in four habitats. The experimental results show that the archaeal structure in the four habitats has no significant variation. In contrast to the bacterial community, the Richness Index-. Shannon-Weaver Index and Simpson index of archaeal were quite lower, and also diminished with degradation.In summary, alpine grassland degradation changed microorganism community structure and diversity, but the bacterial community changed obviously. Bacteria can be used as a good indicator of grassland degradation.