The Impact Of Climate And Planting Structure Changes On Agricultural Greenhouse Gas Emissions And Irrigation Water Demand

During the growth and development of crops,agricultural greenhouse gas emissions and water resource consumption issues arise.With the increasingly prominent contradiction between climate change and human production and life,starting from the perspective of agriculture,using scientific methods to improve agricultural production efficiency,reduce greenhouse gas emissions and water consumption,and improve the ecological environment is an important path for sustainable agricultural development.In order to explore the impact of changes in planting structure on regional agricultural greenhouse gases and irrigation water demand under the background of climate change,based on the DNDC model and Penman Monteith formula,this study assessed the temporal and spatial trends of agricultural greenhouse gas emissions（CO₂,CH₄ and N₂O）and irrigation water demand in the Huang-Huai-Hai region in different periods from 1995 to 2015.The control variates was used to analyze the impact of changes in planting structure,climate and nitrogen fertilizer input on agricultural greenhouse gas emissions and irrigation water demand.The main research findings are as follows:（1）Analyzed the spatiotemporal changes in planting structure,climate,and nitrogen fertilizer input in the Huang-Huai-Hai region during different periods（1995 to 2015）.In terms of planting area,compared to 1995,the total planting area of major food crops（corn,wheat and rice）in 2015 showed an increasing trend,with corn planting area increasing the most,reaching 39%,while wheat and rice planting area increasing slightly,reaching 4%and 6%,respectively.In terms of planting proportion,from 1995to 2015,the planting proportion of wheat showed a weak decreasing trend,the planting proportion of corn showed an increasing trend,and the change in rice planting proportion was not significant;From the analysis of the trend of annual changes in various meteorological elements,it can be seen that the annual average maximum temperature,annual average minimum temperature,and annual precipitation in the study area show a fluctuating and increasing trend.From 1995 to 2015,the climate as a whole developed towards warming and humidifying,while the average annual sunshine hours showed a weak decreasing trend;Compared to 1995,the nitrogen fertilizer input per unit area in the research area showed an increasing trend in 2015.Compared to 1995 and 2015,the number of cities with growth rates of 100-150kg N/ha and>150kg N/ha has significantly increased.（2）The spatiotemporal variation trend of agricultural greenhouse gas emissions（CO₂,CH₄ and N₂O）and irrigation water demand in various cities in the Huang-Huai-Hai region from 1995 to 2015 was clarified.The total emissions of three types of greenhouse gases（CO₂,CH₄ and N₂O）in2015 were 107.643Mt,1.528Mt and 0.127Mt respectively,showing an increasing trend compared to 1995.This may be related to factors such as the increase in planting area of various crops and the impact of human activities,resulting in more carbon and nitrogen elements being discharged into the atmosphere from the soil.At the same time,the global warming potential（GWP）in the study area also shows an increasing trend.The spatial distribution of crop water demand in the research area showed a decreasing trend from the middle to both sides,and the distribution trend of irrigation water demand and crop water demand was similar.Compared to 1995,the irrigation water demand per unit area in most cities in the study area showed a decreasing trend in 2015.（3）Explored the impact mechanism of changes in planting structure,climate,and nitrogen fertilizer input on agricultural greenhouse gas emissions and irrigation water demand in various cities in the Huang-Huai-Hai region.Under the planting structure conditions in 2015,compared to 1995,the emissions of various greenhouse gases（CO₂,CH₄ and N₂O）showed an increasing trend,with an increase of 13.81%,8.60%,and 13.26%,respectively.This is due to the increase in the planting area of various crops（corn,wheat,rice）.At the same time,there are more and more cities in the research area showing an increasing trend in irrigation water demand;Under the climate conditions of 2015,the growth of temperature and precipitation in the study area promoted the emission of various greenhouse gases.The emission intensity of various greenhouse gases（CO₂,CH₄,and N₂O）increased by 5%,0.8%,and26%,respectively.At the same time,due to the significant increase in effective precipitation,the overall irrigation water demand showed a decreasing trend;With the increase of nitrogen fertilizer input,the intensity of N₂O emissions significantly increases,while the intensity of CO₂ and CH₄gas emissions does not change significantly.The increase of N₂O emissions is due to the increase of nitrogen fertilizer application,which provides sufficient substrate for nitrification and denitrification,thus promoting N₂O emissions.