Spatial Trade-offs And Synergies Of Ecosystem Services In The Qingjiang River Basin

In the background of ecological civilization construction and building a moderately prosperous society,promoting the coordinated development of regional economy and environment is a very important topic.The Qingjiang River Basin has a significant ecological strategic position,the economic conditions of which is relatively backward.The green development path is the best way to go.It is necessary to coordinate the contradictory relationship between ecological protection and economic development.In this research,the spatiotemporal patterns of LULC and major ecosystem services was calculated during 1980-2018 in the Qingjiang River Basin.The trade-offs and synergies between four services were analyzed at different scales.In order to explore the trend of ES and their tradeoff and synergistic relationships,a Logistic-CA-Markov model was constructed to simulate the LULC in 2034 under four kinds of scenarios,which were natural growth,arable land protection,ecological protection and ecological construction.The study results shows that:(1)The land use structure is dominated by forest land,and the intensity of land use in the watershed has increased significantly after 2000 compared to the previous period,mainly behaving as the decreasing forest land and increasing construction land and watershed.The above shift pattern has slowed down when the watershed started to pay attention to ecological protection after 2010.After the Shuibuya Hydropower Station in the middle reaches of Qingjiang River started to cut off the flow in 2002,the water volume in the middle reaches of the river ending at the Shuibuya Hydropower Station increased significantly,and the water volume in the Gao Bazhou Reservoir section also increased to a certain extent,resulting in the conversion of forest land to water on both sides of the river.The declined water volume between the Shuibuya and Giheyan Hydropower Station has led to an increase in forest land on both sides of the river.Forest land is the main type which is transferred to construction land,concentrated in the center of Enshi City and some major transportation routes area.(2)Water yield in the Qingjiang River Basin in the past 40 years lies in the interval of 384.78-983.09mm,and the total amount of water produced is between 6.5-16.6 billion square meters.Rainfall is an important factor affecting water yield.Soil retention is 121.48-166.27t/hm2 and the total amount of soil retention is 2.27-3.11 billion tons.The actual amount of soil erosion is 69.99-94.89 t/(hm2·a)and the total amount of erosion is 1.699-2.087 billion tons,the distribution pattern of them is influenced by topographic factors.The high value areas of soil retention are gathered in the valley area on both sides of the middle and lower reaches of the river.The low value areas of soil erosion are distributed in the basin of Lichuan,Jiansi and Enshi,including the plain area in the easternmost estuary.The extent of soil erosion improves with the increase of topographic complexity.Carbon storage is located at 11.50-11.63t/hm2 and total carbon storage is located at 215-218 million tons,with values decreasing year by year,and the distribution is mainly influenced by the structure and distribution of land use.Habitat quality lies between 0.73-0.74,with an increasing trend of decline rate.The low value areas are concentrated in the central built-up areas of the counties,which are obviously disturbed by human activities.(3)The ES trade-offs and synergies relationship has a strong scale-dependent effect.The structure of ES at the basin scale is dominated by water yield.Compared with tributaries,the structure of main streams is more stable,where water yield is the main services in the upper reaches,soil retention and habitat quality in the middle and lower reaches,and carbon storage in the downstream section of Gaobazhou Reservoir.Arable land and grassland are mainly dominated by water yield,while forest land is mainly dominated by carbon storage and habitat quality.Forest plays an important role in carbon storage and habitat quality,and cropland has a greater influence on maintaining soil and water conservation functions.Water yield dominates in plains and high-middle mountainous areas,and soil retention dominates in hilly and low mountainous areas.The low and middle mountainous areas change from soil conservation and habitat quality to soil conservation dominance.The trade-offs and synergies between water yield and other services is more significantly influenced by spatial and temporal scales,the relationships of which are trade-offs in the most of time.The trade-offs and synergies among soil retention,carbon storage and habitat quality are synergistic effects,with carbon storage and habitat quality always being significantly strong synergistic.The hotspot areas in the Qingjiang River Basin were ranked as 1>2>3>4,and their distribution characteristics were influenced by topography and land use patterns.(4)Using the Logistic-CA-Markov model,the land use/cover pattern of the Qingjiang River Basin in 2034 under four simulation scenarios of natural growth,ecological protection,arable land protection and ecological construction can be simulated more accurately.In the four simulation scenarios,there are contradictions in the land use structures of the arable land protection and ecological protection scenarios;the ecological construction scenario can better meet the spatial needs of regional economic construction while meeting the requirements of regional environmental protection,but there is a more obvious conflict between the spatial expansion of arable land and construction land,which is concentrated in the area centered on Enshi city.The four kinds of ecosystem services in the Qingjiang River Basin have different evolutionary patterns.The water yield is at risk of weakening,while soil conservation,carbon storage and habitat quality are improving to different degrees.The absolute gap between the trade-offs and synergies of different ecosystem services in the future maintains an increasing trend in all four scenarios.It is urgent to pay attention to the supply of ecosystem services,coordinate the contradictions and conflicts under different development policies,and guarantee the sustainable development of the basin’s ecosystem.