Simulation Researsh For Impact In Different Climate Scenarios On Soil Organic Carbon Storage Under Land Use Change In Yanqi Basin

Soil organic carbon(SOC)is not only a sensitive indicator of climate change,but also plays an important role in terrestrial carbon cycle.The impact of land use types change on soil organic carbon storage is the core issue of ecological environment effect evaluation.In recent years,a large number of uplands in Yanqi Basin have been abandoned for a long time under the background of climate change,which seriously restricts the carbon sink function of agricultural ecosystem.Yanqi basin is a typical arid oasis basin in Xinjiang,and it is also the core demonstration area of oasis agricultural development in the south slope of Tianshan Mountains.At present,the economy of Yanqi Basin mainly depends on the primary industry,and the quality of agricultural soil seriously affects the economic development of Yanqi Basin.Therefore,in order to evaluate the impact of potential land use change on soil organic carbon reserves under climate change in Yanqi Basin,this paper used point-to-point test and field regional test investigation,and used DNDC model,Arc GIS and two global climate models(BCC-CSM 1.1 and CCSM4)and three representative concentration paths(RCP2.6,RCP4.5and RCP8.5)were used to estimate the soil organic carbon storage(SOCS)and spatial distribution characteristics of the upland in Yanqi Basin,and to simulate the dynamic changes of soil organic carbon storage in upland and upland after abandonment in the next 80 years(2019-2100),This will be of great scientific significance to predict the response of upland carbon storage to climate change and reduce the uncertainty of climate change impact on upland.At the same time,it will provide data support and scientific basis for strengthening ecological management,promoting environmental improvement and increasing farmland soil organic carbon and farmland soil management under future climate change.The results are as follows:(1)The DNDC model can be applied to the Yanqi Basin.The evaluation results of DNDC model in Yanqi Basin as follow:RMSE of simulation value and observation value was 1.1%—2.5%,MAE was 0.01—0.02,R~2 was 92.75%—99.45%,ME was96.02%—99.45%.(2)It is estimated that the upland soil organic carbon storage in Yanqi Basin is 1.32Tg C in 2018,and the soil organic carbon storage under different soil types was quite different.The highest soil organic carbon density of upland in Yanqi basin is 15000—20000 kg C/hm~2,mainly distributed in the middle of Yanqi Basin.The lowest value is10000—15000 kg C/hm~2,mainly distributed in Yanqi County,Bohu county.Under different soil types of upland,the average SOC density under swamp soil is the highest,25400kg C/hm~2,which is much higher than the average SOC density of most soil types in Yanqi Basin.Under different soil types,the average soil organic carbon density under swamp soil(dry period,artificial cultivation of corn)is the highest,which is 25400 kg C/hm~2;the average organic carbon density under stone soil is the lowest,which is13260 kg C/hm~2.(3)In different climate scenarios,the soil organic carbon storage in upland decreased significantly from 2019 to 2100.And the decrease range is smaller in the low emission scenario and larger in the high emission scenario.Under different soil types,the difference is significant,and it is lower than that in 2018.The decrease ratio of soil organic carbon storage in different soil types of upland in 2100 compared with that in2018 is consistent with the change range of total soil organic carbon storage in different scenarios.Under RCP2.6,RCP4.5 and RCP8.5,the SOCS under different soils will decrease by 6%—9.17%,11.02%—15.07%and 16%—23%respectively by 2100compared with 2018.(4)Under different climate models,By 2100,upland abandonment will lead to a sharp decline in soil organic carbon storage,and the decline will be rapid in the high emission and slow in the low emission.Under the two climate models,the upland decreased by 4%at most under the low emission(RCP2.6)and 18%at most under the high emission(RCP8.5);after the upland was abandoned,the upland decreased by 9.17%at most under the low emission and 23%at most under the high emission(RCP8.5).The highest decrease,equal to 14.79?10~7 kg C,was predicted by CCSM4(RCP8.5),and the lowest decrease of 4.29?10~7 kg C by BCC-CSM 1.1(RCP2.6).(5)Under different climate scenarios,in the three periods(2019-2040,2041-2070,2071-2100)after upland abandonment,compared with upland,soil organic carbon storage in these three periods decreased sharply,and in different periods,the decline range was different.In 2040,RCP8.5 in BCC-CSM 1.1 decreased by 3.43%at most,and CCSM4(RCP4.5)decreased by 2.02%at least.In 2070,compared with the SOCS of upland,the minimum decline rate of CCSM4 was 0.8%(RCP4.5);the maximum decline rate of CCSM4 was 7.55%(RCP2.6).In 2100,the SOCS of the abandoned land decreased by 2.84%—15.54%compared with that of the upland.The maximum decrease was 15.54%(RCP8.5)in BCC-CSM 1.1,and the small decrease was 2.84%in BCC-CSM 1.1(RCP2.6).(6)In different climate scenarios,by 2100,when the upland in the simulation study area is abandoned,the soil organic carbon storage will drop sharply.The soil organic carbon storage of different soil types are higher in the upland.This shows that the upland is conducive to the storage of SOC,while the abandoned land is not conducive to the storage of soil organic carbon.