关键词: 退化高寒草甸, 土壤细菌, 物种组成, 群落特征, 生态功能结构

Abstract:

To clarify the response of species composition and functional structure of soil bacteria to grassland environmental degradation in the alpine meadow, the bacteria composition, pattern and function in non-degraded, lightly-degraded, moderately-degraded, severely-degraded and extremely-degraded alpine meadows at the three rivers source region, were studied by high-throughput gene detection techniques. The results showed that the dominant bacteria in alpine meadow soil were Proteobacteria, Acidobacteria, Planctomycetes, Verrucomicrobia and Actinobacteria, and they were accounting for 23%‒29%, 16%‒18%, 9%‒12%, 12%‒14% and 11%‒12%, respectively. The soil bacterial species compositions changed obviously by grassland degradation, the Proteobacteria abundance decreased, while the abundance of Acidobacteria and Planctomycetes increased significantly, and the species on genus level were different at diverse soil layers in degraded alpine meadows. Grassland degradation had no effect on bacterial Chao1 index, lightly-degradation increased bacterial Simpson index, and soil bacterial Shannon index in severly-degraded grassland was the highest. The FAPROTAX functions are mainly composed by Chemoheterotrophy, nitrification, nitrite oxidation and sulfur metabolism. Grassland degradation changed the cycle of carbon, nitrogen, sulfur, iron and manganese, which mediated by microorganisms. Severe and extreme degradation increased the bacterial ammonia-oxidizing function, and decreased the functions of sulfide, nitrite oxidation and ureolysis. In the process of grassland degradation, the bacteriological Chemoheterotrophy, aromatic compounds degradation and the denitrification functions all showed a trend of decreasing first and then increasing variation trends, and the moderate degradation stage was the turning point of the bacterial community ecological functional structure changes. The degradation of alpine meadow changed the soil bacterial community and functional structures. Soil moisture content, pH, total organic carbon, total nitrogen, total potassium, and the ratio of available nitrogen and phosphorus were the main driving factors for the differences in soil bacterial community and functional structures.

Key words: Degraded alpine meadow, soil bacteria, species composition, community characteristics, ecological functional structures