Dominant Ecosystem Services Response Of The Hydro-fluctuation Zone In Hydraulic Engineering Nested Area

The hydro-fluctuation belt of Three Gorges Reservoir is not only a national important ecological functional area,but also an important ecological protection barrier in the upper reaches of the Yangtze River.It is also a fragile transition zone of the ecosystem,providing special ecological,social and economic functions for human beings.It is of great significance to maintain the dynamic balance of the ecosystem and promote the sustainable development of regional ecological economy.Kaizhou District of Chongqing is located in the upstream of Xiaojiang,a tributary of the Yangtze River.The special terrain conditions make it the largest district and county in the Three Gorges Reservoir.The carrying capacity of the ecological system is weak and the ecological environment problems are prominent.In order to solve ecological environment problems in the hydro-fluctuation belt,a hydraulic nested engineering——water level regulation dam has been built in the lower reaches of the new urban area,its normal water level is 170.28 m.which effectively reduces the depth and area of the hydro-fluctuation belt,the problems of regional ecological environment have been properly managed and significantly improved.Under the interactive influence of water level operation of double reservoirs and human activities in the reservoir area,its ecological process is typical and representative compared with other districts and counties in the Three Gorges Reservoir area.Therefore,the research object is the hydraulic engineering nested area of the hydro-fluctuation belt of Kaizhou District.Based on the theory of multi-disciplinary integration,using remote sensing image data,soil data,meteorological data,DEM data,socio-economic data and field sampling survey data,explores the spatio-temporal differentiation of the service and value of water conservation and soil conservation two dominant ecosystem services before and after the construction of hydraulic nested engineering through In VEST model.In this paper,the ecological effect of the hydraulic nested engineering is comprehensively evaluated from the aspects of nature,society and economy,and the ecosystem service function areas are divided comprehensively.In order to provide theoretical support for the ecological protection and repair of the hydro-fluctuation belt and relevant hydraulic nested engineering,and promote the ecological balance and sustainable development of the hydro-fluctuation belt.The main conclusions are as follows:(1)After completion of hydraulic nested engineering,two land use types,orchard and hydraulic construction land,have been added in the hydro-fluctuation belt of Kaizhou district.The increasing trend of swamp grassland,river water surface and inland beach is larger,the decreasing trend of dry land,arbor forest land and paddy field is more obvious,and the other land use types have not changed much.The transfer of land use types mainly occurs between dry land,arbor forest land,swamp grassland,river water surface and inland beach.(2)The value of ecosystem services in the study area increased from 8.742 billion yuan to 11.295 billion yuan in the past 10 years.The high value area is located near the upstream and downstream of the regulating dam,and the area with the most increase in ecosystem service value per unit area is area 2.The highest and lowest value of regional ecosystem services are area 1 and area 3,respectively.From the perspective of water conservation services,the amount of water conservation in the study area decreased by60.72 m~3after the dam was built.The high value area of average amount of water conservation was mainly distributed in area 3 and area 4.The amount of water conservation in area 1 and area 2 decreased significantly.The value of water conservation increased by 2.529 billion yuan,and the value of water conservation per unit area in region 2 increased the most.In terms of soil conservation services,soil conservation in the study area increased by 24800 t after the dam was built.Except for area 4,the other three areas showed a downward trend,and the soil conservation increased 42700 t in area 4.The soil conservation value of the study area increased by0.1 million yuan,and region 1 is the high value area of soil conservation value.(3)The impact of hydraulic nested engineering on the dominant ecosystem services in the hydro-fluctuation belt is generally positive,and all ecological restoration projects have achieved good results.But it is still necessary to pay attention to regional balance and coordinated development to promote the sustainable development of regional ecology-society-economy.According to the distribution index of ecosystem service value,after the hydraulic nested engineering is completed and put into operation,the value of ecosystem service will increase at all levels of topography,and increased first and then decreased with the increase of topography level.The second topography level is the optimal distribution area.After the water level regulating dam was built and put into operation,the main reason for the increase of ecosystem service value in the low-topography level area is the large increase of river water surface,swamp grassland and inland beach area.In terms of Eco-economic coordination,from 2005 to 2015,the ecological and economic coordination degree of the hydro-fluctuation belt in Kaizhou district was 0.034,which was in a low coordination state.Although the social and economic effects of hydraulic nested engineering promote the development of regional social economy to a certain extent,it also increases the potential risk of ecological environment deterioration.The eco-economic harmony degree of area 1 is the highest,the confluence of Donghe River,Nanhe River and Hanfeng lake is a high conflict area,and ecological system of the hydro-fluctuation belt is seriously affected by the social and economic development.From the perspective of population-economy mismatch,the degree of mismatch between the eco-economy and population in the study area is increasing,and the degree of disharmony in the development of eco-economy is expanding.Area 1 is a highly developed area of eco-economy in the study area,and area2 and area 3 are under developed areas of ecological economy.The population ecological economy matching degree of area 4 tends to be close to the overall level of the study area.According to comprehensive ecosystem service functional areas,the proportion of general,medium,high and extremely important functional areas was24.89%,25.98%,26.47%and 22.65%respectively.The key ecological functional areas account for about 50%of the study area,mainly distributed in the areas with high altitude and high woody vegetation coverage.