Effects Of Land Use And Management On Soil Carbon And Nitrogen Mineralization Of Alpine Grassland

Change of land use patterns and management are the core factor of soil quality and environmental change, which also causes soil productivity and ecological environmental problems, and that, soil carbon and nitrogen are mainly indicative parameter. We illustrated these ways in the research:lab incubation,15N isotope labeling, added cow dung and urea and sugar, fenced grassland. The research aimed at that the dynamic mineralization of soil carbon and nitrogen in alpine meadow and farmland transformed into solar greenhouse vegetable field, added cow dung and urea and sugar in fenced grassland of alpine meadow, deteriorate artificial grassland and deteriorate pasture and native meadow in Qinghai Sanjinagyuan, thus revealing the effect of soil carbon and nitrogen bank under land use patterns and management, and also provide basic information about land use patterns and management. The results were listed as follows:(1) Under laboratory conditions, the soil CO2-C accumulation in farmland was higher than in alpine meadow, and its also was higher in alpine meadow than in1-year-old greenhouse and5-year-old greenhouse, but the difference was no significant in soil organic carbon mineralization and its accumulation in alpine meadow, farmland,1-year-old greenhouse,5-year-old greenhouse soil (P>0.05) after28days. The soil nitrogen mineralization capacity of the alpine meadow was stronger than that of farmland,1-year-old greenhouse and5-year-old greenhouse. The soil nitrogen mineralization capacity of farmland was weaker than that of alpine meadow,1-year-old greenhouse and5-year-old greenhouse, while they were similar between1-year-old greenhouse and5-year-old greenhouse. These soil carbon and nitrogen mineralization mainly occurred during the first culitivation stage after treatment (0～7d or0～3d).(2) Under laboratory conditions, soil carbon and nitrogen mineralization total product in grazing were higher than fenced after added cow dung and urea and sugar treatments. Sugar addition stimulates soil nitrogen fixation in a short-term (0～7d), and urea and cow dung stimulates soil nitrogen mineralization. By15N isotope tracer showed:soil microbes used nitrogen efficiency is higher in grazing than in fenced, and added urea stimulates soil microbes used nitrogen mainly occurred during the first seven days (0～7d), but together added urea and sugar mainly occurred during the end days (7～56d). (3) Soil carbon mineralization rate were higher in meadow than in deteriorate artificial grassland and deteriorate pasture in Qinhai sanjiangyuan native (P<0.05), and there were no significant difference deteriorate artificial grassland and deteriorate pasture (P>0.05). The soil CO2-C accumulation in native meadow was higher than deteriorate artificial grassland and deteriorate pasture after28days. When incubate temperature is five centigrade, the soil nitrogen mineralization capacity of the native meadow was stronger than that of deteriorate artificial grassland and deteriorate pasture; when incubate temperature are fifteen or twenty five, the soil nitrogen mineralization capacity of the deteriorate pasture was stronger than that of deteriorate artificial grassland and native meadow. However, the soil mineralization process was similar among different soil types.(4) With the incubation temperature increase, temperature sensitivity of native meadow soil respiration was stronger than that of deteriorate artificial grassland and deteriorate pasture. Temperature sensitivity of soil nitrogen mineralization in the5℃-15℃was weaker than that of15℃-25℃.In conclusion, conversion of grassland to farmland or greenhouse on the soil nitrogen mineralization abilities was weakened, but the difference was no significant in soil organic carbon mineralization accumulation in alpine meadow, farmland,1-year-old greenhouse,5-year-old greenhouse soil (P>0.05) after28days. Soil carbon and nitrogen mineralization total product in grazing were higher than fenced after added cow dung and urea and sugar treatments. Carbon and nitrogen addition stimulates soil respiration in a short-term (0-14d), but the difference was no significant in soil organic carbon mineralization accumulation in fenced and grazing. When global warming, temperature sensitivity of native meadow soil respiration was stronger than that of the deteriorate artificial grassland and deteriorate pasture, and the15℃is transition temperature of the soil nitrogen mineralization temperature sensitivity.