Carbon Processes In Meadow Steppe And Its Response To Fencing In Northern Slope Of The Tianshan Mountain

Grassland ecosystem is an important component of the terrestrial ecosystem. Therefore, studying the variation of the carbon cycle has important significance for understanding the material cycles in the terrestrial ecosystem. With global climate change, the grassland ecosystem carbon cycle has become a research hot spot, and the observation of meadow steppe ecosystem is relatively scarce. This research uses the Li-8100 automated soil CO2 flux system and static chamber method(Li-840 CO2/H2 O infrared analyzer) to study carbon dynamics in Gan gou, 50 km in the southwest of Urumqi. Soil respiration and the ecological system respiration of meadow steppe inside and outside of the fencing were also observed in situ. The soil, root, vegetation of the fencing inside and outside were investigated, and the temperature, moisture and other environmental factors were monitored. The main conclusions are as follows:1 After comparative Analysis of enclosure and grazing meadow soil carbon density, aboveground vegetation carbon density and carbon density of root system, we found that, after 8 years of fenced meadow grassland soil carbon density and carbon density were higher than grazing roots in different soil layers, especially for the 0~10 cm soil layer(P<0.01).The carbon density of plant in fencing area was significantly higher than that at the grazing district(P<0.01) in every month. Therefore, the fencing section of meadow steppe promoted carbon storage capacity, and significantly increased the meadow soil and vegetation carbon storage.2 Whether inside or outside of the fencing, the mountain meadow steppe soil respiration showed obvious diurnal and seasonal variations, a single peak curve. Grazing did not change the variation of soil respiration rate, the peak is especially obvious from May to August, while no obvious peak was observed in April, September, and October. The size of carbon emission was higher than that in the other in July 6, in particular, the greatest contribution to soil respiration and total carbon emissions. In general, after enclosure of carbon emissions is significantly higher than that outside the fence.3 Temperature and humidity are two important factors affecting soil respiration, but the temperature plays a leading role. In the mountain meadow steppe, no significant correlation between soil respiration and soil water content; while soil respiration and soil temperature have a significant positive correlation, illustrating that temperature is the dominant factor controlling the mountain meadow grassland soil respiration. Inside and outside the fence of the shallow soil(0~5cm), the correlation is higher than those at other soil depths, and in all levels of soil, the correlation between soil respiration and temperature inside the fence were higher than those outside the fence, reflecting the change of soil respiration could be better monitored by 5cm geothermal energy.4 The mountain meadow steppe, whether inside or outside the fence, ecosystem carbon exchange showed obvious diurnal and seasonal variations, showed a single peak curve. Grazing has no impact on the variation of carbon flux. Form May to August, carbon absorption was obviously higher than that outside the fence, while in other months it is the carbon source. Inside the fence, the 5~8 month in the ecosystem carbon uptake in the larger contribution, so after enclosure meadow grassland in season for carbon sink. While outside the fence is because of the summer in carbon absorption contribution is small, thus performing as carbon source.5 Temperature and humidity are two important factors of ecosystem carbon exchange, but the temperature plays a leading role. In the mountain meadow steppe, ecosystem carbon exchange correlation with soil water content was not significant; ecosystem carbon exchange has a significant linear correlation with temperature, temperature is the dominant factor determining the mountain meadow grassland carbon exchange.