| The agro-pastoral ecotone in Northern Shaanxi is located in the transition zone from the Mu Us sandy land to the Loess Plateau.The farming and animal husbandry in this area has obvious transitional characteristics,fragile ecological environment and shortage of water resources.At present,the scale of sandy land management and utilization in the area has been expanded,and the agricultural water consumption has been increasing.If the current trend of disorderly expansion is still maintained,when the development scale exceeds the support capacity of water resources,it will threaten the natural drought,water shortage and fragile ecological conditions,and directly affect the sustainable development of economy and society.Therefore,coordinating the relationship between resource development and ecological protection is of decisive significance for the sustainable development of regional agricultural economy.Aiming at the problems of water scarcity and fragile ecological environment in study area,in this paper,the key role of water resources in regional economic development and ecological protection is clarified,and the simulation and prediction of water resources are carried out;a regulation model of sandy agricultural utilization was constructed and the improved NSGA-II multi-objective optimization algorithm was used to explore the appropriate scale of sandy land agricultural utilization under the regulation of water resources.This paper is to provide support for sustainable utilization of resources,sustainable development of ecological environment and stable improvement of economy and society in the ecotone.The main results are as follows:(1)Based on VAR model,the dynamic impact of water resources on agricultural development in ecotone was analyzed,and the key role of water resources in the development of sandy land agriculture was clarified.In this paper,the correlation analysis of water resources,agricultural economy,land use,ecological environment and other closely related indicators in the process of agricultural development is carried out.Based on the typical indicators,a multivariable VAR model is established.The impact of water resources on other indicators in the process of agricultural development in the ecotone is quantitatively analyzed by using impulse response and variance decomposition.The results showed that the comprehensive proportion of water resources contributed 94.44%,90.93%,58.86%,86.39%and 70.93%to the total water consumption,agricultural water consumption,total output value of agriculture,forestry,animal husbandry and fishery,sandy land area and ecological service value,respectively,which indicated that water resources played a key role in agricultural development in the ecotone,and was the main influencing factor and resource driving force.(2)Based on TOPMODEL and WAS model,the natural and social dual water cycle in the ecotone was simulated,and the water resources available in the future was predicted.TOPMODEL model is used to simulate surface runoff based on DEM.Heuristic segmentation algorithm is adopted to analyze the mutation point of historical runoff data.1979 is determined as the year of mutation point.1980-2000 is divided into periodic rate period and 2001-2018 as validation period.The efficiency coefficients of periodic rate period and validation period are 0.87 and 0.79 respectively,which meet the accuracy requirements of the model.Taking the runoff process under the future climate model as the input,the water supply of the ecotone was simulated by the was model.The results show that the water supply of the ecotone under RCP2.6,RCP4.5 and RCP8.5 rainfall scenarios of Beijing climate model BCC-CSM1.1 is 1.514 billion m3,1.446 billion m3 and 1.470 billion m3 in 2025,and 1.884 billion m3,1.845 billion m3 and 1.872 billion m3 in 2030.(3)The water resource regulation model of sandy land agricultural utilization is constructed,and the multi-regulate scenarios are set up.According to the interval quantification principle of agricultural water available in sand land,the water threshold is defined.The available water amount of sandy land in 2018 and 2025 is 19113×104m3?17880.5×104m3,in RCP2.6,RCP4.5 and RCP8.5 rainfall scenarios is 25571.6×104m3?23928.8×104m3?26390.8×104m3 respectively.Based on the Markov model,the land use types in the ecotone were predicted,and the exploitable sandy land scale of sandy land agricultural use in 2025 and 2030 were 2992.41km2 and 2763.72km2 respectively.From the perspective of water resource conditions,water-saving measures and crop planting structure,the regulation scenarios were set up,including three rainfall scenarios,three water-saving scenarios and seven planting scenarios,forming a total of 63 scheme sets.(4)Based on the thoery of o ? strategy of dominant mechanism,the NSGA-? algorithm is improved to solve the water resources regulation model.Based on the principle of the largest scale of agricultural use of sandy land,15 recommended schemes were selected.Under each scheme,the proportion of exploitable scale in unused sandy land in Yuyang District and Shenmu county was the lowest,and the largest proportion in 2018,2025 and 2030 were(18.57%,4.08%),(7.06%,28.6%)and(5.01%,0%)respectively;Fugu County and Dingbian County accounted for the highest proportion,which were(100%,31.24%),(100%,47.82%)and(100%,100%)respectively.The largest exploitable scale of the ecotone in 2018,2025 and 2030 accounted for 24.54%,14.71%and 29.99%respectively.In general,the spatial distribution of agricultural use scale in the ecotone is high in the East and West.The results show that,under the premise of relying on the diversion and diversion project,the water resources in the staggered zone can not support the full development of unused sand land in all situations,and the distribution of water resources is uneven and the situation is tight.(5)The spatial matching pattern of soil and water resources in the interlaced zone is studied by using the method of matching index of soil and water resources.The distribution range of the matching coefficient of agricultural soil and water resources in the interlaced zone is[53.07122.14],and the available water amount and utilization scale of the sandy land show a mismatch status.In time and space,the matching coefficient between Yuyang District and Shenmu county was always<0,which showed that there were "more land and less water",and the available water of sandy land was insufficient;The index range of Fugu County in 2018,2025 and 2030 is[1.77,1.98],[3.36,5.84],[-0.39,1.71],and the available water quantity of sand land and development scale are kept in the balanced range,and the matching of soil and water resources is the best;The matching pattern of soil and water resources in the ecotone shows a transition from more water in the northeast to less water in the southwest.The uneven development of sandy land agriculture leads to spatial difference in the matching pattern of soil and water resources in each county and region.The improvement of water-saving efficiency is helpful to improve the matching degree of soil and water resources.The efficient agricultural irrigation management measures are still an effective way to improve the matching pattern of soil and water resources in the interlaced zone. |
PDF Full Text Request