Simulation Of GHG Emissions In Double Cropping Paddy Field

Rice is an important food crop in China,and ensuring rice yield plays an important role in food security.At the same time,rice fields are also an important source of greenhouse gas emissions from agriculture.In recent years,the change of double cropping rice planting area,on the one hand,comes from social and economic factors,on the other hand,it is also related to climate change.Therefore,in order to evaluate the rice yield and greenhouse gas（GHG）changes under climate change and rice multiple cropping,the main production areas of double cropping rice in southern China were selected as the research areas.Firstly,based on the agricultural gas observation data of rice,the rice variety pool in DNDC model was expanded and improved through GLUE module in DSSAT model.At the same time,the concept of agro-ecological zone in AEZ model was used to divide rice-producing areas in China.With the help of GIS technology,the greenhouse gas（GHG）in paddy fields can be simulated and assessed at site scale and national scale.At the same time,we used multi-model climate data to assess greenhouse gas emissions from double cropping paddy fields under future climate conditions（2050s,2041-2070）and estimated the changes of greenhouse gas emissions under multiple cropping changes in southern China during 1990-2015.The main conclusions are as follows:（1）The effects of climate change on greenhouse gas emissions from double cropping rice in China were analyzed.There was a significant positive correlation between temperature and methane emissions from paddy fields.The higher the temperature,the more methane emissions.This means that if the rice planting system,varieties and field management measures remain unchanged,rice fields will have higher methane emissions under future climate conditions.Nitrous oxide showed no sensitivity to climate change.（2）The emission of CH₄ and N₂O from double cropping rice is generally higher than that from single cropping rice.In the future,the emission of CH₄ and N₂O from double cropping rice will increase in varying degrees,but the difference between single cropping rice and double cropping rice will not change much with historical conditions.In addition,nitrogen application is an important factor affecting the intensity of greenhouse gas emissions.Excess nitrogen is released in the form of greenhouse gases due to excessive nitrogen application.Under climate change,methane emissions of Single-cropping and double-cropping rice increase in varying degrees,and the lower the latitude,the greater the difference between single-cropping and double-cropping rice emissions.（3）Based on the study of rice ecological zoning and previous studies on multiple cropping changes in southern China,the greenhouse gas emissions of paddy fields caused by multiple cropping changes in southern China were estimated.It was found that the global warming potential decreased by 23%and the yield decreased by only9%.The results showed that the warming potential of double cropping rice was generally higher than that of single cropping rice.Climate warming has increased greenhouse gas emissions from paddy fields and reduced rice production.It is estimated that the multiple cropping changes in double-cropping rice areas in southern China resulted in a small reduction in rice yield,but significantly reduced greenhouse gas emissions from paddy fields and alleviated the effect of paddy field warming.Under the background of climate warming,it will become an important reference for rice production adaptation measures in the future.