Evaluation Of Ecosystem Service In The Core Water Source Area Of The Middle Route Of The South-North Water Diversion Project Based On InVEST Model

Ecosystem services are all the benefits that humans derive directly or indirectly from ecosystems.Quantitative assessment of regional ecosystem services is of great significance to ecological environment construction,rational utilization of natural resources and sustainable economic and social development.Irrational human activities will lead to serious degradation of ecosystem services,resulting in ecological problems.To alleviate the beijing-tianjin region of south-to-north water transfer project in shortage of water resource present situation,the optimized configuration of water resources is of great significance,danjiangkou reservoir area as the core,the main forest of south-to-north water transfer project is an important water source protected area at the national level,the ecological environment situation and water safety,directly related to the south-to-north water transfer project of water safety and engineering benefit.Taking the core water source area of the middle route of the South-to-North Water Diversion Project as the research area,this paper comprehensively utilizes meteorological,soil,land use/cover,DEM data and relevant statistical data,employs In VEST model,and combines with geographic information technology.Four ecosystem services including water conservation,soil and water conservation,water purification and habitat quality were quantitatively evaluated in the water source region from 2005 to 2015.Geo DA correlation analysis was used to explain the trade-offs and synergies among ecosystem services.Quantitative analysis of the impact of land use/cover change on ecosystem services;And the importance of ecosystem service function is partitioned.The main contents and results of this paper are as follows:(1)Water conservation function in water source areas:the spatial distribution trend of water conservation is"high in the west and north,followed by the middle and low in the east".From the perspective of land use/cover type,the water conservation function of shrub land is the strongest,while that of construction land is the weakest.(2)Soil and water conservation function in the water source area:the total amount of soil erosion in the water source area decreased by 53.96×10~6 t during the ten years,and the soil erosion showed a distribution trend of"high in the west of China and low in the east".From the perspective of land use/cover type,the water and soil conservation function of construction land is the strongest,while that of unused land is the weakest.(3)Water purification function in water source area:the total output of nitrogen and phosphorus in water source area decreased by 270.66 t and 29.02 t,respectively,during the ten years.The main reason for the decrease of local nitrogen and phosphorus output was the conversion of cultivated land and rural residential land into water body and agricultural and forestry land.The spatial distribution trend of N and P output was consistent.The high value was distributed in the eastern plain,and the low value was distributed in the western,northern and central mountainous areas.The cultivated land was the main source of N and P output.(4)Habitat quality in the water source area:The spatial distribution of habitat quality was significantly different.The high value area was mainly distributed in Funiu Mountain National Nature Reserve in the eastern part of Qinling Mountains in the northern part of the water source area,while the low value area was concentrated in the agricultural production area in the southeastern plain.From the perspective of land use/cover type,the average habitat quality index of forest land was the highest,and the average habitat quality index of rural residential land was the lowest.(5)Tradeoffs and synergies among ecosystem service functions:The spatial aggregation characteristics of the four ecosystem service functions are mainly synergies,and trade-offs exist or are not significant in some regions.Habitat quality and water conservation function were not significant in the south of Xichuan County and the north of Danjiangkou City,but the synergistic relationship was prominent in the other areas.The trade-off relationship between habitat quality and water and soil conservation function is mainly distributed in irrigation valley,Danjiangkou reservoir area and the northern area of Danjiangkou city.The trade-off between water purification function and habitat quality was mainly distributed in the southeastern part of Yunyang region and the hilly region from Danjiang River valley to the eastern part of Qinling Mountains.The tradeoff between water and soil conservation function and water purification function is mainly concentrated in Hanjiang River Valley and Danjiang River Valley.Water conservation function,water and soil conservation function and water purification function are mainly synergistic,and the trade-off relationship is mainly distributed in the Danjiangkou reservoir area,the irrigation valley area,the Hanjiang River valley area and the low hilly area from the Hanshui River to the northern Daheng Mountain.(6)The area proportions of ecosystem services in water source areas were 16.40%,36.29%,27.54%and 19.77%,respectively,of general importance,medium importance,importance and extreme importance.The critical importance is mainly distributed in the northern Funiu Mountain area and the middle and low mountain areas in the west and south of the water source area.The importance distributed centrally in the middle and low hilly areas on both sides of the Danjiang Valley,and mixed in the west and north of the water source area.