Experimental Study Of Influence Factors On Soil CO₂Release Rate

Laboratory tests on two type of soil Total Organic Carbon of which is1.03%and3.95%respectively from Nanjing, China have been carried out to study the relation between temperature,moisture,test methods,seasons,microbes and organic matter content and soil CO2release rate, and the related mechanisms is analysed according to test results, the corresponding findings are presented as follows:(1) Under low moisture content (8-10%), CO2release rate of the specimens varies little in10-60℃; In18.60-37.89%moisture content range, CO2release rate of the specimens (TOC1.03%) increases with temperature, Q10decreases first and then increases with temperature and the minimum value is at45℃; In19.20-28.98%moisture content range, CO2release rate of the specimens (TOC3.95%) increases first and then decreases and then increases with temperature, and Q10decreases first and then increases; Meanwhile, it is concluded through test results that the relation between soil CO2release rate and temperature is determined by both microbial decomposition and thermal decomposition, and thermal decomposition become dominate instead of microbial decomposition in organic matter decomposition under high temperature.(2) At12℃, CO2release rate of specimens (TOC1.03%) varies little with moisture in8.64-37.89%, under other temperatures, the optimal moisture content range is18.60-28.98%, CO2release is limited both by low and high soil moisture content, and Q10increases with moisture in8.64-18.60%and varies little with moisture in18.60-28.98%; CO2release rate of specimens (TOC3.95%) increases with moisture in9.12-28.98%under different temperature, the optimal moisture content is not found but increasing rate becomes slow, and Q10varies little and is stable in0-2under high temperature, and Q10increases with moisture in9.12-19.2%and decreases with moisture in19.2-28.98%under low temperature. These phenomenon is determined by both enzyme and O2.(3) The CO2release rate of specimens (TOC1.03%. MC18.60%) tested with direct warming method is greater than which tested with continuous warming in10-60℃, and the difference increases with temperature; The optimal temperature is discovered in10-60℃with continues warming method, and the optimal temperature is50℃; The data tested with continuous warming method is lower, and it is caused by substrate loss, and substrate loss increases with temperature, therefore, the data tested with direct method is more accurate.(4) In laboratory test, the variable of season will also change CO2release rate of specimens, and CO2release rate of specimens in winter is greater than which in summer, but the Q10law is similar, and this phenomenon is related to the temperature flexibility of soil microbes.(5) CO2release rate of specimens after sterilization decreases distinctly, but release rate still exists, the results indicate that microbes do dominate soil organic matter decomposition and CO2release and have strong ability of rebirth.(6) CO2release rate of specimens increases with soil organic matter content, and the curves between CO2release rate of specimens (TOC3.95%,1.03%) and temperature are different under high temperature, this phenomenon is related to the difference of organic matter content and components.