Simulation Research For Impact By Climate Change On Productivity And Soil Organic Carbon Of Chinese Main Grassland

Chinese grassland is broad with abundant species,and it is an important carbon pool of terrestrial ecosystem.Grassland productivity and soil carbon are the main components of the carbon pools of grassland ecosystem.In recent decades,Chinese main grassland had been degraded under climate changes,which seriously restricts the carbon sink function of grassland ecosystem.Therefore,in order to clarify the impact of climate change on the carbon storage of grassland ecosystem,as well as reveals the response of productivity and soil organic carbon to different greenhouse gas emission scenarios in the future,based on the CENTURY model,took the alpine meadow,alpine grassland,alpine desert of Qinghai-tibet plateau and the temperate meadow,temperate grassland,temperate desert of inner Mongolia as the research object,analyzd the response of the changes of the grassland productivity and soil organic carbon to its climate change from 1960 to 2015,and simulated the change characteristics of grassland productivity and soil organic carbon in different future periods(2016-2099)under different greenhouse gas emission scenarios.The main conclusions are as follows:(1)The results of multi-parameter localization in CENTURY model showed that this model could simulate the productivity and soil organic carbon of Chinese main grassland.Among verifications,the determination coefficient of soil organic carbon was 0.75~0.94.(2)The temperature of Chinese main grassland increased in 1960~2015,as well as the rise of average minimum temperature was largest,which was 0.54?/10a.As for different grassland types,the increase of temperature alpine meadow was highest,which reached 0.61?/10a.In different future scenarios,the temperature of the alpine regions would increase by 2.2~4.1?,and the temperate region would increase by 4.4~7.4?,in addition,the rise of temperate meadow steppe would be 5.4~8.9?.The precipitation of Chinese main grassland in 1960-2015 fluctuated greatly,and the changes of precipitation in different types of grassland were different.Among the changes,the precipitation of the alpine grassland has increased 35 mm since 2000,while the precipitation in the temperate meadow grassland has decreased 46 mm.As for different future scenarios,precipitation in RCP8.5 scenario is more than that in RCP4.5 scenario,among them,the precipitation of alpine desert would increase by5%~10%,and the precipitation of temperate meadow grassland would not change significantly in RCP4.5 scenario,which would increase by 9%to 32%in RCP8.5 scenario.(3)From 1960 to 2015,the trends of productivity change in different types of Chinese main grassland were different.Among them,the productivity of alpine meadow increased continuously,and the growth rate reached 9.89g/m~2/10a after 2000.The productivity fluctuations of the temperate typical steppe from 1960 to 2000 were strong,with the maximum increase or decrease of 40g/m~2/10a or-35g/m~2/10a respectively.In different future scenarios,there would be an increase in the productivity of each type of grasslands.Among them,the alpine meadow would increase by 12~22%,the alpine grassland would increase by 43%~59%,the alpine desert would increase by 250%~340%,the warm meadow grassland would increase by 16%~53%,the temperature typical grassland would increase by33%~66%,and the temperate desert grassland would increase by 6%~38%.(4)From 1960 to 2015,the soil organic carbon of the alpine grassland decreased significantly(R~2=0.79).The active soil organic carbon of alpine meadow,alpine steppe,alpine desert,temperate meadow steppe,temperate typical steppe,temperate desert was accounted for 0.98%,0.82%,0.74%,1.74%,1.63%,1.65%of the total reserves respectively,while slow soil organic carbon proportion was59.71%,58.57%,50.43%,55.26%,50.43%,62.82%respectively.In different future scenarios,the soil organic carbon of different types in alpine region grasslands would increase significantly,while that of different types in temperate regions grasslands would decrease,among them,the highest growth rate would be 3.0%(RCP4.5)of alpine desert,while the largest decline would be-3.6%(RCP8.5)of temperate typical steppe.The comparison about changes of the divided carbon pools in future grasslands showed a decreasing trend of the active organic carbon in the temperate grassland(-2.9%,RCP8.5)and the temperate desert grassland(-4.4%,RCP8.5),but the other types would increase,with the highest one in alpine desert,which would reach 6.0%(RCP8.5).In terms of slow soil organic carbon,the reserves of different alpine grassland types would increase in different degrees,while that of the different temperat grassland types would show a decreasing trend,among them,the highest amplitude would appeare in the alpine desert and the temperate typical steppe,which would reach 5.8%(RCP4.5)and-5.8%(RCP8.5) respectively.