Response Of SOM Decomposition To Temperature Change In Zoige Alpine Wetland,China

Zoige alpine wetland,which lies in the east edge of Qinghai-Tibetan plateau and belongs to the third pole of the world,is considered to be very sensitive to future climate warming and soil moisture decreasing.At the same time,there was the periodic warming and cooling generally existing around the clock,seasonal and interannual scales.Whether there was inconsistent response in the process of soil organic matter decomposition during climate warming and cooling will be significant for predicting future carbon(C)budget of terrestrial ecosystem.Therefore,understanding changes in soil organic matter(SOM)decomposition,temperature sensitivity(Q10)and their mechanism in alpine wetlands response to warming and drying is important for assessing scientific problems of carbon source or sink in alpine wetland and providing important theoretical basis for carbon balance function of terrestrial ecosystem response to climate change.Here,we established a sampling gradient from the wetland edge to the meadow in the Zoige alpine wetland in China,which represented a gradient of decreasing soil moisture.We conducted incubation experiments in thermostat(8-28?)and thermode(6-30?)to investigate changes in SOM decomposition and Q10during degradation process of alpine wetland to alpine meadow.What's more,we explored the inconsistent response and mechanism of SOM decomposition to climate warming and cooling.The conclusions as follows.(1)Temperature significantly influenced SOM decomposition rates in all sampling locations.SOM decomposition rate first increased and then decreased with decreasing soil moisture,which indicated that drying of these wetlands would enhance internal SOM decomposition.However,Q10 and activation energy(Ea)showed no apparent trends with changing soil moisture.Overall Q10 values in the wetland(1.50)were significantly lower than that of the meadow(1.83);similar trends were found for Ea.(2)Ea was negatively logarithmic correlated with carbon quality indices in all plots,which suggested that the carbon quality-temperature hypothesis is applicable to alpine wetlands and meadows.The responses of SOM decomposition and Qio in alpine wetlands to future declines in wetland area and soil moisture are discussed.(3)The rate of SOM decomposition in warming process is significantly greater than it in cooling process(F=7.194,P<0.001;F=10.810,P<0.001).The average rate of SOM decomposition during warming(R~2=0.523,P=0.523;R~2=0.511,P=0.003)and cooling(R~2=0.835,P<0.001;R~2=0.277,P=0.001)are significantly linear decrease in alpine wetland and meadow with the increase of incubation time.The Qio of SOM decomposition in cooling process(4.80,5.20)was significantly higher than the Q10(1.80;1.80)in warming process(F=8.379,P<0.001;F=18.441,P<0.001).(4)The Qio of SOM decomposition was significantly positive correlation with soil microbial carbon and nitrogen(R~2=0.418,P=0.418;R~2=0.600,P<0.001).The Q10 of SOM decomposition in cooling process was significantly positively correlation to soil soluble organic carbon in alpine wetland(relevant coefficient was 0.731),and was significantly negative correlation to soil soluble organic nitrogen(relevant coefficient was 0.756).The Q10 of SOM decomposition in cooling process was significantly positive correlation to soil soluble organic carbon in alpine meadow(relevant coefficient was 0.866),and was significantly positive correlation to soil microbial nitrogen(relevant coefficient was 0.837).In addition,there was significant positive correlation with soil pH value and negative correlation with oxidation reduction potential(ORP)during warming and cooling.The microorganism and substrate supply drove the inconsistent response of SOM decomposition to the process of climate warming and cooling,which should be controlled by the quantity of microorganisms and the quantity and quality of substrate.