Ecological Water Requirement Of Natural Vegetation In Shule River Basin Based On Spatial Optimization Of Biocapacity

Ecological overshoot has been a common problem in inland river basins in arid land.Shule River Basin,a typical arid inland river basin,is located in the northern sand prevention belt of China,is also the important node of"One Belt And One Road"In the Shule River Basin,climate is arid,water resources are scarce,and the ecological environment is very fragile.With the increase of population,human needs for Biocapacity are increasing day by day,and the problem of ecological overshoot is particularly prominent.The optimization of Biocapacity is the efficacious way to maintain the sustainable supply of Biocapacity and solve the problem of ecological overshoot.However,water resources in arid inland river basins are an important limiting factor for the optimization of Biocapacity,especially the natural vegetation,as the main provider of Biocapacity,has a strong dependence on ecological water requirement.Therefore,the rational allocation of ecological water requirement is the key to ensure the optimization of Biocapacity of natural vegetation.The ecological water requirement of natural vegetation under the spatial optimization pattern of Biocapacity of natural vegetation in inland river basins in arid land has not been thoroughly studied at home and abroad at present.Therefore,this paper aimed at this key scientific problem,took the Shule River Basin as an example,and based on meteorological data and remote sensing data with the support of remote sensing and GIS technology,based on the Penman-Monteith formula and the ecological footprint of vegetation net primary productivity(NPP-EF),this paper estimated the water consumption and Biocapacity of natural vegetation in the Shule River Basin from 2000to 2018,and analyzed their spatial and temporal patterns and their spatial correlation.Based on this,a Biocapacity optimization model based on cellular automata model was constructed,and three scenarios of Biocapacity optimization were set up and carried out in this basin.Then,the water consumption of vegetation was taken as the ecological water demand of vegetation,and the ecological water requirement of natural vegetation was quantitatively estimated under three scenarios,and the spatial allocation and regulation policy suggestions of the ecological water requirement of the basin were put forward,in order to provide reference for the regulation of ecological water resources in the basin.The main conclusions are as follows:(1)From 2000 to 2018,the total water consumption of natural vegetation in the Shule River Basin showed a trend of first increasing and then decreasing,and the average total water consumption of natural vegetation in the basin was 14.86×10~8m~3.Spatially,the water consumption of natural vegetation in the southern Qilian Mountains was the highest,followed by that in the central plain region and the lowest in the northern Mazong Mountain region.The water consumption of low coverage grassland was the highest,while that of forest land was the least.Water consumption per unit area of natural vegetation presented forest land>shrubland>sparse forest land>high coverage grassland>medium coverage grassland>low coverage grassland.(2)From 2001 to 2018,Biocapacity in the Shule River Basin showed fluctuating increasing trend.Spatially,the Biocapacity of Qilian Mountain region was the largest,the Biocapacity of central plain region was the second,and the Biocapacity of Mazong Mountain region was the smallest.The total Biocapacity of all land use types showed the sequence of Unused land>Grassland>Plowland>Forestland>City and Rural construction land>Water area.The Biocapacity per unit area shows the law of Plowland>City and Rural construction land>Forestland>Grassland>Water area>Unused land.(3)The water consumption of natural vegetation and Biocapacity in the Shule River Basin were positively correlated to some extent in space.The area with high vegetation water consumption and high Biocapacity accounted for 11.43%of the total area of natural vegetation;The area with low vegetation water consumption and low Biocapacity accounted for 33.08%.(4)Compared with the base year(2018),the spatial patterns of Biocapacity under the three optimal scenarios did not change much,but the heterogeneity of internal changes was obvious.Among them,the total Biocapacity under the scenario with the highest probability of land use suitability decreased by 203730.68wha.The total Biocapacity of the basin under the maximum Biocapacity scenario increased by76700.25wha.The total Biocapacity of the basin under the ecological sustainable development scenario decreased by 82300.57wha.(5)Compared with the base year(2018),The spatial pattern of natural vegetation ecological water requirement under the three optimal Biocapacity scenarios did not change much.The vegetation ecological water requirement in the southern Qilian Mountain region was the largest,followed by the central plain region,and the northern Mazong Mountain region was the least.Compared with the base year,the total ecological water requirement of the three scenarios increased.Among them,the total vegetation ecological water requirement under the scenario with the highest probability of land use suitability was 16.86×10~8m~3,which was 2.40×10~8m~3 higher than that in the base year.The total vegetation ecological water requirement under the maximum Biocapacity scenario was 17.30×10~8m~3,which was 2.84×10~8m~3 higher than that in the base year.The total vegetation ecological water requirement under the ecological sustainable development scenario was 17.97×10~8m~3,which was 3.51×10~8m~3 higher than that in the base year.