A Study On Water And Soil Conservation Function Of Ecosystem Services In The Three Gorges Reservoir Area

Water conservation and soil maintenance are crucial to the ecological security of the Three Gorges reservoir area.Water conservation continues to provide water to the inside and outside of the ecosystem through redistribution of precipitation.Soil conservation is an important guarantee for the ecosystem to prevent erosion and maintain ecological security,and the Three Gorges Reservoir Area is an important soil conservation area in China.Therefore,it is very important to study the water conservation and soil retention function of the Three Gorges Reservoir ecosystem.In this paper,the seasonal water yield module of the In VEST model and the RUSLE combined with remote sensing and geographic information system technology were used to analyze the spatial and temporal distribution patterns of water conservation and soil conservation in the ecosystem from 1990 to 2015 in the Three Gorges Reservoir area.And analyze its driving factors.The main conclusions of the study are as follows:(1)From 1990 to 2015,the trend of the average value of water conservation depth and total water conservation in the Three Gorges Reservoir area was volatility increased.The total water conservation in the Three Gorges Reservoir Area in 1990,1995,2000,2005,2010 and 2015 were15.873 billion m~3,16.603 billion m~3,16.934 billion m~3,18.604 billion m~3,17.518 billion m~3,17.458 billion m~3.The total amount of water conservation increased from 15.873 billion m~3in1990 to 17.458 billion m~3in 2015.The Increment was 1.585 billion m~3and the growth rate was9.98%.The fluctuation trend of water conservation in the reservoir area is mainly related to the interannual rainfall fluctuation.The growth trend is mainly related to the increase of vegetation,especially the increase of forest area.(2)There is obvious spatial heterogeneity of the water conservation in the Three Gorges reservoir area.The forest water conservation function showed an upward trend with increasing slope and altitude,but the increasing trend is not significant,and the water conservation depth of per unit area fluctuated less with time.Areas with high average value of water conservation depth in the reservoir area are mainly distributed in areas with high elevation and steep slopes.(3)NDVI,altitude,slope and rainfall had a significant positive correlation with water conservation depth,while temperature,population had a significant negative correlation with water conservation.The factors that affected water conservation in the Three Gorges Reservoir area were mainly climate and policy.The rainfall affected the source of water conservation,and temperature affected its evapotranspiration ability.Policy factors indirectly affected water conservation by affecting land types.The contribution of policy factors to the increase of water conservation in the TGRA was 1.531 billion m~3,which was the main source of the increase in water conservation.(4)From 1990 to 2015,the soil conservation and the total soil conservation per unit area of the Three Gorges Reservoir area showed a volatile growth trend.From 1990 to 2015,the soil retention per unit area were 1051.35,1028.75,1174.42,1213.68,1191.43,1406.6t/hm~2.The total amount of soil conservation increased from 5.992 billion tons in 1990 to 7.939 billion tons in2015.The Increment was 1.947 billion m~3and the growth rate was 24.52%.(5)There is obvious spatial heterogeneity of the soil conservation in the Three Gorges reservoir area.The overall trend is high in the north and low in the south,and high in the east and low in the west.The high-value areas of soil conservation per unit area are mainly concentrated in forest land cover areas.The contribution rate of construction land and farmland to soil conservation is low.The main high-value areas of soil retention are distributed in areas with high altitude and steep slopes,with less human disturbance and better vegetation restoration.(6)Altitude,slope,woodland area,and population density were significantly correlated with soil retention.The main influencing factors of soil conservation was policy factors,and the conversion of farmland to forest project in the policy factors contributed to the increase of soil conservation of 535 million tons.In the short term,by changing the ecosystem structure and process of TGRA,such as afforestation projects can reduce Soil Erosion.