Effects Of Active Carbon Limitation And Microbial Community Responses On Temperature Sensitivity Of Soil Respiratio

Changes in labile carbon pools and microbial communities are the primary factors controlling soil respiration（Rs）in warming experiments.The response of Rs to climate change,which usually is called temperature sensitivity of Rs(Q₁₀),is of great significance for predicting possible feedback between global carbon cycle and climate system.However,their relative importance of labile carbon and microbial community response to soil respiration temperature sensitivity is still unclear,especially in the context of global warming.Their relative contributions have caused considerable uncertainty in predicting the feedback of carbon cycle to climate change.This study revealed the relative contribution of labile carbon limitation and soil microbial community to soil respiration under drying-rewetting cycle（DWC）and warming.Using two long-term experimental soils representing different SOC pools（old-field for 15 years,and bare-fallow for 15 years,represent more labile C and stable C,respectively）,three soil treatments were made:（a）bare-fallow soils were sterilized then inoculated with old-field soil microbes（LC）to assess the labile C limitation effects,while controlling for microbial community responses;or（b）soil microbes from the bare-fallow were used to inoculate sterilized old-field soils（MC）to assess the microbial community effects,while controlling for labile C limitation;（c）sterilized old-field soils were inoculated with microbes extracted old-field soils to serve as Controls for LC and MC.The three soils of LC,MC and Control were conducted a 60-d laboratory incubation experiment at 22 and 32℃.The incubation experiment included six10-d DWC of two treatments:one mean constant-moisture treatment at 60%water-holding capacity（WHC）,and a DWC treatment with 10-d drying to 20%WHC and immediately rewetting to 100%WHC.The main results of as follows:（1）In the constant treatment,the result of cumulative soil respiration（CSR）was:Control>MC>LC,which indicated that both labile C limitation and microbial community response can reduce soil respiration,and the influence of labile C limitation was greater.However,in the dry-wet cycle treatment,Control=LC>MC,which indicated that under DWC conditions,labile C limitation had no effect on soil respiration,and microbial community response can reduce soil respiration.（2）Q₁₀ of Control decreased with the extension of culture time,while Q₁₀of LC increased with the increase of culture time,and Q₁₀of MC was relatively stable with the change of time.Compared with Control and MC,the temperature sensitivity of LC is greater,while that of MC is lower than that of Control.Taking together,the results showed that DWC lifted the limitation of labile carbon and changed the relative contribution of labile carbon limitation and microbial community response to soil respiration.Under the condition of short-term warming,microbial community response can reduce the temperature sensitivity of soil respiration more than labile C limitation.