Simulation Study On Carbon Cycle Of Farmland Ecosystem In The Subsidence Area Of Coal Mining Based On DNDC Model

In order to quantify the disturbance influences of exploitation of coal field working face on the carbon cycle of farmland ecosystem,protect the ecological environment in mining areas and realize the sustainable development of farmland ecosystem in subsidence areas of coal mining,this article carried out a research on a mining area of Shanxi Jincheng Anthracite Mining Group Co.,Ltd.By selecting a subsidence area developed by coal mining activities as the experimental area,choosing a farming area where physical and chemical properties of soil and farmland management measures were basically the same with that for the subsidence area as the contrast area and relying on sampling experiment and long-term observation,the applicability of DNDC model in this mining area was verified.Then,the revised model was adopted to simulate and predict the carbon cycle process of farmland ecosystem in both subsidence area and contrast area.Meanwhile,the disturbance influences of subsidence area of coal mining on the farmland ecosystem were systematically analyzed.Furthermore,with the model,farmland output and emission quantity of greenhouse gases for the subsidence areas of coal mining with different slopes were predicted,according to which the farmland management measures specific to the subsidence area of coal mining were proposed.It came to major conclusions as follows:(1)DNDC model can properly stimulate the carbon cycle process of farmland ecosystem in the research area.(2)Compared with the contrast area,the subsidence area of coal mining witnessed a decline in organic carbon content,vegetation NPP,CO2 emission of soil and soil methane absorption while its soil erosion and carbon loss were remarkably increased,indicating that a carbon loss effect were presenting on the soil of the subsidence areas of coal mining as a whole.(3)Studying the yield and greenhouse gas emissions of coal mining subsidence area under different slope,the results showed when the subsidence slope gradient over 12 degrees,the crop yield and the grain warming potential increased sharply,therefore,the gradient should be less than 12 degrees in coal mining subsidence area to weaken the effect on yield and greenhouse gas emissions.With the comprehensive consideration of yield and GWP,the optimization management measures of low carbon tillage in mining subsidence stable areas are put forward.That is to improve the conventional fertilization amount to 306 kg N/ha,enhance the original tillage depth from 20cm to 30cm and return all straw to the field.