Response Of Carbon Budget Of Biological Soil Crust-soil System To Simulated Warming In Alpine Sand Area

Biological soil crust is an important type of surface cover in alpine sandy areas,which is of great significance in windbreak,sand fixation and ecological restoration.However,research on the effects of warming on the carbon budget of biological soil crust-soil system in alpine regions is scarce,which can not reflect the response of biological soil crusts to climate change in alpine ecosystem.In this study,in the Gonghe Basin of Qinghai,the moss and algae crusts which were widely developed in the artificial vegetation restoration area were taken as the research object.The passive warming device OTC was used to simulate the warming.The daily and monthly dynamics of carbon budget rate of two types of biological soil crust-soil system under the condition of experimental warming were observed.The effects of warming on carbon budget and sensitivity were discussed.The main conclusions were as follows:(1)The daily dynamics of carbon release rate and net carbon release rate of moss and algae crust-soil system showed a "single peak" curve,the daily peak value of carbon release rate appeared around 13:00,and net carbon release rate appeared around 14:00,the existence of biological soil crusts advanced the daily peak value of soil carbon release rate appear about 2hours;and the daily dynamics of carbon fixation rate showed a "double-peak" curve,the daily peaks appeared at 11:00 and 20:00 respectively.The monthly dynamics of each component(carbon release rate,carbon fixation rate and net carbon release rate)showed a "single peak" curve,with the maximum value appearing around August and the minimum value appearing around January.(2)The daily and monthly dynamics of each component of moss and algal crust-soil system were not changed by warming,but the peak value and occurrence time changed.Under the condition of relative drought,when the warming was moderate,the daily peak value of each component would appear earlier,and the peak value would increase,and the average value of each component of the growing season would increase;when the warming was excessive,the daily peak value of each component would appear earlier,but the peak value would decrease,and the average value of each component of the growing season would decrease too,but they were all larger than that of non warming treatment.Under the condition of relative humidity,warming delayed the occurrence of daily peak value of carbon release rate and carbon fixation rate of the two types crust-soil system,and the peak value increased,but the daily peak value of net carbon release rate decreased,and the average value of each component of growing season were all increased.(3)The presence of moss and algae crusts reduced the temperature sensitivity of soil carbon release during the growing season,Q10 values of bare land,moss and algal crust-soil system fluctuated from 1.47 to 2.62,1.29 to 2.10 and 1.34 to 2.13,respectively.The warming changed the temperature sensitivity of two types crust-soil system.In relative drought condition,the warming reduced the temperature sensitivity,the higher the increase of temperature,the smaller the Q10 value;in relative humidity condition,the higher the increase of temperature,the greater the Q10 value,and the long-term warming could reduce the temperature sensitivity of growing season of biological soil crust-soil system and appear adaptive changes.(4)The development of biological soil crusts increased the soil carbon release and fixation,it enhanced the carbon "source" effect of carbon exchange between soil and atmosphere.The warming promoted its carbon "source" effect.In the case of relative drought,the greater the increase of temperature,the weaker the promotion effect;in the case of relative humidity,the greater the increase of temperature,the stronger the promotion effect.