The Response Of Ecosystem Carbon Exchange To Different Stocking Rates In Stipa Breviflora Desert Steppe

Ecologists pay more attention to climate warming in recent years, which caused by elevated atmospheric CO2 concentration. Grassland has huge carbon sequestration potential because of its vast area. Grazing is the main utilization way of grassland, livestock regulated the grassland productivity, community structure, soil physical and chemical properties through foraging and trampling, then indirectly change the carbon cycle balance between grassland ecosystem and atmosphere. At the same time, water and temperature factors are also the key factors of restricting the grassland carbon input and output.In this study, we choose Stipa breviflora desert grassland under different stocking rates to measure CO2 exchange rate between grassland ecosystem and atmosphere in the daily, monthly, yearly scales, respectively, to observe the tendency of standing crops of plants community, functional group and dominant species, vegetation coverage, the underground biomass, soil temperature, soil moisture, soil organic carbon content, air temperature and precipitation. We try to explore the response of desert grassland ecosystem carbon exchange rate to different sheep stocking rates, and to reveal the mechanism of how vegetation, soil and environmental factors effect on carbon exchange.The results showed as followes.1. Long-term overgrazing caused the standing crops proportion of perennial bunch grasses increase significantly in the community, meanwhile the standing crops proportion of forbs, shrubs and semi-shrubs decreased, C4 species’standing crops proportion raised in the community.2. Eecosystem carbon exchange was effected by stocking rates and precipitation commonly. However, precipitation could reduce the response of ecosystem carbon exchange to stoking rates.3. The increase of accumulative underground biomass, net root biomass and soil organic carbon content could cause the growth of soil respiration rate.4. Soil moisture, air temperature and soil temperature had effect on ecosystem carbon exchange rate.