The Study Of Community Diversity And Soil Active Organic Carbon Pool Characteristics Under Different Utilizations In Alpine Grassland

Soil organic carbon pool of grassland is one of the largest carbon pools in the terrestrial ecosystems. The ways of grassland utilization have an important influence on the species diversity, organic carbon and its active components. Taken the different fencing time(long-term fencing, short-term fencing) of the Bayanbulak alpine grassland and the different grazing(moderate grazing, farming and grazing) as the study objects in the article, the grassland community diversity characteristics, soil organic carbon and its active components(particulate organic carbon、readily oxidizable carbon、microbial biomass carbon),distribution proportion and profile distribution characteristics were analyzed, and taking the carbon pool management index as the quantified index to evaluate grassland soil quality changes. Conclusions are as follows:The grassland community diversity characteristics(Diversity index、Evenness index、Dominance index) had different responses to different utilizations in the study. The general result of the three indexes showed: MG>A+G>LF>SF. Moderate grazing improved species diversity and species dominance; diversity index and dominance index were decreased after fencing. The four different utilization ways had no significant influence on grassland evenness.The grassland community diversity characteristics were significantly positive correlated with readily oxidizable carbon and total nitrogen only in 0~10 cm; which were significantly negative correlated with most soil nutrients in 10~30 cm.The soil organic carbon had different responses to utilization in the study, and its general result showed: SF>LF>MG>A+G, which showed that short-term fencing had a significant effect on organic carbon accumulation; under the agriculture, the organic carbon lossed significantly.The changing characteristics of soil particulate organic carbon and its distribution proportion were correspond with organic carbon, and its general result showed:SF>LF>MG>A+G, which showed that short-term fencing was helpful to particulate organic carbon accumulation, improving soil carbon pool activity; grazing, agriculture and grazing decreased the activity of soil carbon. The contents of particulate organic carbon, distributionproportion in different utilizations and the changing range among soil layers were greater than that of organic carbon, which showed that they were more sensitive to external change.The soil readily oxidizable carbon had different responses to different utilizations in the study, and the general result showed: SF>LF>A+G>MG. Fencing improved the contents of soil readily oxidizable carbon effectively, especially in 15~50 cm soil layers, there was a significant difference from other utilizations. While the readily oxidizable carbon distribution proportion showed: A+G>LF>SF>MG, there was difference whit the changing trend of readily oxidizable carbon. The changing range of oxidizable carbon and its distribution proportion were greater than organic carbon. It showed they can become sensitivity indexes to indicate the influence of different utilizations on the stability of grassland carbon pool.The response of microbial biomass and its microbial quotient to utilizations in the study results showed: LF>MG>SF>A+G,in which there was greater difference from the variation characteristics of organic, the other active organic and its distribution proportion, which showed that the carbon pool stability was not only affected by its activity, but also by other environmental factors and human factors. So the conclusion was different.The carbon pool management index of different utilizations results showed:SF(112.30)>A+G(100.00)>LF(90.65)>MG(87.44). It showed that short-term fencing had positive significance to grassland quality recovery, and with the increase of the readily oxidizable carbon content, the carbon pool management index was improved more significantly. There were significant correlated between carbon pool management index and grassland community diversity characteristics in 0-30 cm soil layer. Which showed that the CPMI can be used as indication to indicating grassland community diversity characteristics.