The Impact Of Grassland, Grazing On Soil Microbial Biomass On The Eastern Tibetan Plateau

The Tibetan Plateau plays an important role in water conservation and global climate regulation, showing a serious degradation because of the climate changing and overgrazing, it has threatened the ecological balance, biodiversity conservation and economic development. Soil microbial biomass is more sensitive than other soil physical-chemical properties in soil quality, and is recognized as early warning indicators of soil ecosystem in recent years, it has been increasingly used in the evaluation of damage or rehabilitation of the ecosystems. In order to explore the change and relationship between the soil physical-chemical properties and microbial biomass on eastern Tibet Plateau, we did a research on soil microbial biomass of different grassland types and grazing intensity, the results are as follows.1. The study is about the soil microbial biomass of different grassland types with different soil depth in Ganna region (alpine meadow, alpine shrub meadow, sub-alpine meadow, swamping meadow and upland meadow), which is in Gansu Province.1) The soil respiration and microbial carbon of same grassland type decrease with their increasing depth, it maybe because of more organic matter, more appropriate environment and more effective organic matter in top depth, which are conducive to the growth and proliferation of the microorganism, the increase of metabolic quotient with its soil depth shows that the ripening of the top depth is higher than that of bottom depth.2) The microbial biomass of swamping meadow is the highest and upland meadow is the lowest. Through to the biological community structure by the ratio of microbial carbon and nitrogen, we can infer that the number of fungi in alpine meadow and upland meadow soils are higher, and the bacteria numbers are higher in the soils of the other grassland types. There are significant positive correlation (P<0.01) between soil respiration, microbial carbon and moisture content, organic carbon, total nitrogen, and a significant negative correlation (P<0.01) between metabolic quotient and moisture content, organic carbon, total nitrogen.2. The study is about the soil grazing impact of different sampling time in swamping meadow (non-grazing, seasonal-grazing and full-grazing).1) The soil moisture decreases significantly because of the increasing bare of ground, the order of moisture content in May, July, September are: non-grazing>full-grazing>seasonal-grazing, soil organic carbon, total nitrogen and respiration are the highest in non-grazing area in different time.2) The results show that the grazing intensity has significant impact on soil organic carbon, total nitrogen, respiration, and no impact on microbial carbon, nitrogen. There is a significant positive correlation (P<0.01) between soil respiration and water content, organic carbon, total nitrogen, and a significant positive correlation (P<0.01) between total nitrogen and water content, organic carbon.3. The study is about the soil grazing impact of alpine meadow for two years (light-grazing, middle-grazing and heavy-grazing), the results show that:soil moisture of two years decrease with increasing grazing intensity, the pH value increases with the increasing grazing intensity, microbial carbon decreases in2010and increases in2011.The results showed that the soil microbial biomass of different grazing treatment have no differences, the difference between moisture content and pH value, microbial biomass carbon is significantly (P<0.01).