The Study Of Soil Respiration Of Qilian Spruce And Steppe In The Upstream Of Heihe River

Carbon dioxide released from the soil is considered to be one of the largest flux in the carbon cycle of the earth, slight changes of Soil respiration will have an enormous impact on the concentration of CO2in the atmosphere,, exacerbate or mitigate global climate change.Similarly, reducing soil CO2emission and increasing soil carbon storage can reduce the concentration of CO2in the atmosphere. Studies have shown that high-latitude and high-altitude ecosystem is more sensitive and rapid response to the temperature rise. Qilian Mountain is located at the junction of the Qinghai-Tibet Plateau and the Loess Plateau and desert in Inner Mongolia and Xinjiang, plateau ecosystem is fragile and sensitive to changes in the global climate, its unique terrestrial ecosystems play an important role in the global climate and the carbon budget.In this paper, CO2flux was measured understory Picea crassifolia forest and sub-alpine meadow in Qilian Mountains using Li-8100Automated Soil CO2Flux System in growing season in the field, Study the temporal variation of the flux and the correlation with temperature and humidity and other environmental factors. For the following main conclusions:Diurnal variation of soil respiration in Picea crassifolia forest results show that, CO2flux released from the earth’s surface increases on the basis of soil respiration due to the covering of moss and litter and the CO2flux released from the earth’s surface into the atmosphere in August is more than50%than that in June.The max flux in June had better consistency with near-Earth temperature; in mid-August growing season, the maximum flux on moss surface had better consistency with soil temperature.CO2fluxes on litter surface and cleared litter surface, moss surface and de-moss surface reached the maximum in late July to early August throughout the growing season, at this time, the average near-Earth temperature and soil temperature reached maximum value. Soil moisture reached the maximum value in mid-August during the entire growing season. The measured CO2fluxes and soil temperature and air temperature reached a significant level whether or not to remove moss or litter, correlation between CO2flux on the moss surface de-moss surface and soil temperature greater than the temperature of near-Earth,CO2fluxes on litter surface and cleared litter surface showed a high correlation with air temperature and soil temperature. Using soil moisture and soil temperature to explain the changes in soil CO2fluxes common can improve the degree of explanation on moss surface and de-moss surface. But had no significant effect on the CO2flux on the litter surface and cleared litter surface.Van’t Hoff model can better express the relationship between soil CO2flux, total CO2fluxes and soil temperature, near-Earth temperature, can explain about50%-70%soil respiration. But the simulation between soil moisture and carbon fluxes through the linear model, quadratic model, power function model showed no significant relationship.diurnal variation of Subalpine meadow results show whether or not to remove the above-ground parts of plants, the maximum value of ecosystem respiration and soil respiration had good synchronization with near-Earth temperature.Soil respiration and ecosystem respiration reached maximum at about13:00-15:00. Compare the maximum of soil respiration and ecosystem respiration, the minimum of the soil moisture and the maximum of the soil temperature had hysteresis. The minimum of soil moisture was around17:00. The minimum soil respiration was around5:00-7:00am.The monthly variation resulted:CO2released in the natural meadow state was30%more comparing with soil respiration which was mowed.Compared with the soil respiration which was removed the above-ground parts of plants, The maximum value of ecosystem respiration in advance at the end of July, with an average of36.3%more than mowing.The average of soil temperature was12.1℃. the average of near-earth air temperature was15.54℃,1.8%and6.3%lower than mowing. Little change in soil moisture before September, an average of43.7%.1.4%more than mowing.Index and polynomial model can better expressed the relationship between Soil respiration and air temperature, and the explain rate of soil temperature observations can be improved20%-30%if removed observations at nights when using exponential model.Q10value displayed in the growing season, with the month increased, The amount of soil respiration has a tendency to increase in the same night temperature.Ecosystem respiration have a significant correlation with near-earth air temperature and soil temperature and can be explained60%of the ecosystem respiration variation, removal of night-time observations can improve the fitting accuracy of the results.The Q10value shows that raising the same temperature, the CO2released rate of ecosystem respiration was larger than that of soil respiration.Relatively high correlation of soil respiration and the water and heat conditions of soil20cm-60cm layers, followed by solar radiation and atmospheric conditions caused by solar radiation; ecosystem respiration between solar radiation and atmospheric conditions caused by solar radiation have a very clear correlation, and have relatively less effects by the water and heat conditions of surface and20cm-60cm soil layers.