Study On Soil Carbon Change And Its Control Simulation In Small Coal-bearing Watershed Farmland Based On DNDC Model

As a strong land disturbance activity,coal mining has serious disturbance effects on farmland carbon cycle and crops.In order to protect farmland soil organic carbon,improve soil fertility and productivity,promote the sustainable development of agriculture in the mining area and improve the ecological environment,Changhe River basin,a typical small coal-bearing watershed taken as an example,the spatial-temporal changes of soil organic carbon stocks,crop yields,CO2 and CH4 in Changhe River basin were simulated and analyzed by using DNDC model during 2015-2016.And the influence of coal mining on the disturbance of farmland soil organic carbon,crop yield and greenhouse gas emissions was evaluated.On this basis,taking winter-wheat as an example,the low-carbon cultivation of watershed farmland was optimized for regulation and simulation.The main conclusions are as follows(1)The localization verification results of DNDC model show that the simulated and measured values of model are in good agreement,which indicates that the model with a good applicability in the study area,and can be used to simulate the farmland soil carbon cycle and crop yield.(2)From 2015 to 2016,the soil organic carbon stocks,winter wheat yield,and CO2 emissions in farmland in the Changhe River basin have been reduced to varying degrees from temporal dimension,with a decrease of 700 tons,1014 tons,and 433.92 tons,respectively.In terms of spatial distribution,both the farmland soil organic carbon reserves and winter wheat yield losses show obvious spatial differences.The loss is small in the plain areas on both sides of the Changhe river,the loss of the low hills located on the east side of the Changhe River basin followed,while the losses on the mining sites located on the west side are larger.(3)In the optimization simulation of low-carbon cultivation of farmland in the Changhe River basin,it was found that regulation of terrain slope,adjustment of the amount of fertilizer and depth of cultivation all have an important impact on the yield and GWP value per unit yield of winter wheat based on DNDC model.On the basis of quantitative analysis of these individual control measures,a combined optimization measure was proposed to reduce the terrain slope of farmland areas with winter-wheat to about 10°,increase the amount of fertilizer by 20%,and adjust the depth of cultivation to 30 cm,thus the yield of winter wheat in Changhe River basin will increase 2452t,GWP will reduce 1218 tons of CO2 equivalent.