Vulnerability Evaluation And Planting Structure Regulation And Optimization Of Agricultural Soil And Water Resources System In Heilongjiang Province

With the large-scale development of cultivated land,the problems such as the decline of cultivated land quality caused by farmland soil and water loss and water level drop are becoming more and more serious,and the degradation characteristics of agricultural soil and water resources system have become increasingly prominent,directly restricting the safety of regional food production.Vulnerability as the basis for evaluating regional development and the criterion for measuring future development planning,quantitative and accurate assessment of agricultural soil and water resources system vulnerability is of great significance to ensure national food security and agricultural sustainable development.The purpose of this study is to explore the vulnerability assessment methods of agricultural soil and water resources system in Heilongjiang Province,and to establish prediction and control model.Taking 13 regions in Heilongjiang Province as the study area,taking agricultural water and soil resources as a compound system,the agricultural soil and water resources system vulnerability is evaluated based on the matching analysis of soil and water resources,and then the regulation strategy of agricultural planting structure is explored.First of all,as an indispensable part of water consumption in crop production,the gray water footprint was included in the water footprint,and the water footprint was used as a characterization parameter of water resources,and the matching degree of agricultural soil and water resources was discussed from the point of view of crop production;Secondly,the matching coefficient was included in the evaluation index to establish the vulnerability evaluation index system,and the temporal and spatial variation law of vulnerability was clarified by calculating the vulnerability index.Thirdly,the key driving factors of vulnerability were screened,and the response law of driving factors to vulnerability was analyzed;Then,different development scenarios were set,and qualitative and quantitative methods were used to predict the future evolution of vulnerability;Finally,vulnerability was taken as a constraint to regulate the layout of agricultural planting structure.The main research results are as follows:(1)A generalized matching model of agricultural soil and water resources was constructed.Taking water footprint of crop production as the characterization parameter of water resource,we took into account the influence of crop types and climatic conditions on the matching pattern of agricultural soil and water resources,calculated the water footprint of crop production in Heilongjiang Province,and constructed a generalized matching model.The matching relationship of agricultural soil and water resources in Heilongjiang Province was described.The matching of agricultural soil and water resources does not change significantly with time,and the matching pattern is deteriorated from southwest to northeast in space.(2)A vulnerability assessment method including matching coefficient was established.The matching coefficient of agricultural soil and water resources was regarded as the basic characteristic of soil and water resources,and the gray water footprint,as an index reflecting the pollution degree of agricultural chemical fertilizer,was incorporated into the vulnerability evaluation index system.Using swarm intelligence algorithm(taking seagull optimization algorithm and dragonfly algorithm as examples)to optimize random forest model,the vulnerability assessment method of agricultural soil and water resources system in Heilongjiang Province was established.(3)The driving mechanism of the vulnerability of agricultural soil and water resources system was clarified.Based on the criterion layer and index layer of vulnerability evaluation index system,the vulnerability driving mechanism of agricultural soil and water resources system was analyzed by using obstacle function model.The soil and water resources criterion layer has the greatest driving effect on vulnerability,and the driving effect of obstacle factors in the ecological structure criterion layer appears year by year.(4)The future evolution trend prediction method of the vulnerability of agricultural soil and water resources system was constructed.Based on the research of driving mechanism,quantitative and qualitative methods were used to predict the future evolution of vulnerability:The vulnerability evolution trend of agricultural soil and water resources system is different under different scenarios,without policy guidance and technical support,agricultural soil and water resources system develops to a vulnerable situation;Taking into account economy,technology and water conservation can effectively ensure the good operation of agricultural soil and water resources system.(5)The optimization model of agricultural planting structure with vulnerability constraints was constructed.Taking the economic,social and ecological benefits as the goal,the non-dominant sorting genetic algorithm with elite strategy(NSGA-II)was used to optimize the agricultural planting structure: Under different development scenarios,the proportion of planting area of rice,corn and soybean in the optimization of agricultural planting structure is between 19.82% and 26.53%,37.98% and 45.96% and 23.31% and 26.71%,respectively.Compared with non-vulnerability constraints,vulnerability constraints limit the proportion of rice planting area,improve the ecological benefits of agricultural soil and water resources system,and restrain the growth of economic and social benefits.