Simulation And Optimization Of Farmland Ecosystem Services In The Taihu Lake Basin

Agroecosystem is the common product of natural environment and human activities,and it is an important ecosystem,which provides more than half of the global food supply.However,in the past few decades,due to the transformation of land use and unreasonable human management methods,a series of eco-environmental problems have been triggered,resulting in the trend of continuous degradation of global agroecosystem services.With the rapid development of social economy,food security and ecological security have become prominent problems on the road of sustainable development in our country.Using observed data to calibrate the APSIM model,this paper evaluates the temporal and spatial changes of three types of ecosystem services(food supply services-grain yield,water quality regulation services-nitrogen loss,climate regulation services-N₂O emissions,SOC accumulation)under the agroecosystem of Taihu Lake basin,analyze the changing rule of the three categories of ecosystem services,weigh the trade-off relationship and influencing mechanism.Through the combination of reduced fertilization(0%,-20%,-30%,-40%)and straw returning(non-straw return,rice straw return and non-wheat straw return,wheat straw return and non-rice straw return,All straw return),16 scenarios were constructed to simulate the change trend of four types of ecosystem services from2018 to 2035,and the better management model was selected by using Pareto optimal theory and linear weighting method.To provide scientific basis for optimal management and regulation of farmland in Taihu Lake basin.The main conclusions are as follows:(1)From 1986 to 2017,grain yiled and SOC accumulation showed a downward trend,nitrogen loss showed a fluctuating upward trend in the early period and a downward trend in the later period,and N₂O emissions showed a temporary downward trend after a continuous rise.Spatially,the four types of service indicators showed a high degree of overlap,with high-value areas concentrated in the east and southeast of Taihu Lake basin and low-value areas in the northwest.(2)The relationship between grain yield and nitrogen loss,grain yield and N₂O emission,nitrogen loss and N₂O emission,N₂O emission and SOC accumulation services are mainly associated with synergistic relationship,while there is a trade-off relationship between grain yield and SOC accumulation,nitrogen loss and SOC accumulation service.Among them,the synergistic relationship between grain yield and nitrogen loss and N₂O emission is negative,that is,it is undesirable synergies.(3)Meteorological factors,soil factors and fertilization factors are the main driving factors affecting grain yield,nitrogen loss,N₂O emission and SOC accumulation services,among which fertilization has the most prominent impact on the four types of service indicators,showing a significant positive correlation.(4)Through 16 scenario simulation studies,it was concluded that fertilization promoted grain yield,nitrogen loss and N₂O emission,significantly promoted SOC accumulation service in the early stage,but had no significant effect in the later stage,straw returning could promote grain yield,SOC accumulation and inhibit nitrogen loss,but increased N₂O emission.The effects of various modes of straw returning on ecosystem services are as follows:All straw return>rice straw return and non-wheat straw return>wheat straw return and non-rice straw return>non-straw return.(5)Based on linear weighting and Pareto optimal theory,the scheme of maximizing the comprehensive benefits of grain yield,nitrogen loss,N₂O emission and SOC cumulative service was screened.It was suggested that the farmland management mode of reducing fertilization by 20%and returning rice and wheat straw to the field should be implemented in Taihu Lake Basin.