Carbon Cycle Environmental Sensitivity Analysis Of Typical Grassland

Ecological system carbon cycle is the current hot spot of ecology research. We measured different enclosed period and grazing community CO2NEE diurnal variation and their sensitivity to environmental factors, typical steppe in Xilinhaote using the dynamic open chamber made by ourself. Compare the similarities and differences and the correlation with the small scale chamber method data and the large scale eddy covariance data measured at the same time. This study provide the basic data to the estimate of carbon sequestration、the data match and scale transformation between the small scale CO2NEE data measured by the chamber and the large scale eddy covariance data. The main conclusion is as follow:1. The CO2NEE daily variation of the enclosed grassland mainly shows the double absorption peak curve. The trend is as follow:the CO2NEE change to negative value after the sunrise, reach to the negative peak in the morning, then the community photosynthetic rate decline gradually, CO2NEE increased and change to positive value in the noon, afternoon the light intensity begin to reduce, and reach to another negative value about two hours before sunset. The CO2NEE daily variation of the free grazing grassland shows a single peak curve. The trend is as follow:the CO2NEE is positive value in the night, in the daytime because of the vegetation degeneration、low productivity, so the photosynthesis is weak, the respiration enhanced with the increase of light and temperature, the community net CO2release is increased and reach to the peak in the noon, then decreased in the afternoon.2. Through the analysis of effectively photosynthetic active radiation of grassland communities in the afternoon and before sunset, the research found, that in the total situations effectively photosynthetic active radiation has positive correlation with community CO2assimilation rate, whereas in some local situations, they have negative correlation; The community are sensitive to radiation in its response threshold (between light compensation points and light saturation ones), and the basic trend is the crest vs trough. But as the positive correlation of the overall trend, it does not follow the variation discipline of radiation, and the correlation of temperature is significantly higher than the radiation.3. The change of the community CO2flux affected by both temperature and their own rhythm.4. By analyzing the large scale eddy covariance data of the same period, except several irregular data, the observation results were most consistent of the enclosed plots of27years and5years, but the results from the free grazing plot are opposite.