Temporal And Spatial Evolution Of Ecosystem Services In The Luanhe River Basin And Scenario Simulation

The Luanhe River Basin is an important ecological barrier for urban agglomerations in northern China and an important water conservation area in the Beijing-Tianjin-Hebei region.Various ecosystem services within the basin play an important role in ensuring ecological security and green socio-economic development in the Beijing-Tianj in-Hebei region.Therefore,it is of great practical significance to study the spatiotemporal evolution and to simulate the ecosystem services under different scenarios in the Luanhe River Basin.This paper quantitatively evaluates the three ecosystem services of soil conservation,water conservation,and water quality purification in the Luanhe River basin during 2005,2010,2015,and 2020,analyzes the trade-offs and synergies among various services,as well as the influencing factors of ecosystem services,and simulates the development of ecosystem services in the basin in the future.The main results are as follows:(1)Assessment of current ecosystem services.The overall soil erosion level in the Luanhe River basin belongs to moderate and mild erosion,and the sub basins with large erosion modulus are mainly distributed in the southern and central parts of the Luanhe River basin;During the study period,the four-year average soil conservation amount in the watershed was 5.87 × 109 t,soil conservation capacity gradually increased from northwest to southeast.The average annual water yield of the basin is 1.942 billion m3,and the average water conservation amount is 492 million m3.The water conservation depth increases from northwest to southeast.Xinglong County and Kuancheng County are areas with high water conservation depth.The average values of TN and TP retention in the watershed are 35481 t and 2266 t,respectively,accounting for 95.8%and 96.4%of the total load.The high value areas of nitrogen and phosphorus retention are mainly distributed in the agricultural and animal husbandry ecotone of the Bashang Plateau,and in the valleys and farmland areas in the middle of the watershed.(2)Soil erosion in subbasins is significantly correlated with river water quality;The overall relationship between soil conservation and water conservation services is synergistic,while the relationships of soil conservation-water quality purification and water conservation-water quality purification are transitioning from synergy to trade-off.The intensity of soil conservation has a linear positive correlation with the change of precipitation,while the amount of water conservation has a positive correlation with precipitation,and a negative correlation with potential evapotranspiration.The overall retention capacity of TN and TP in the watershed increases(decreases)with the increase(decrease)of precipitation in ecological area A,and decreases(increases)with the increase(decrease)of precipitation in ecological area B.The intensity of ecosystem services varies under different land use patterns.(3)Under the scenarios of future shared socio-economic paths(SSPs),the land use change in the watershed is significant,with the area of farmland and woodland in the watershed significantly expanding under the SSP3 scenario,while the area of construction land expanding is the largest under the SSP5 scenario.Using the spatial distribution of land use under each scenario to simulate changes in ecosystem services,it was found that soil conservation services in the central region of the watershed were weakened under each scenario,while water conservation and water purification services were enhanced.The soil conservation intensity of the watershed was the largest under the SSP5 scenario,the total water conservation amount was the largest under the SSP1 scenario,and the TN and TP retention amounts were the largest under the SSP3 scenario.The intensity of watershed ecosystem services under different scenarios is closely related to the development path of the watershed.According to the changing characteristics of ecosystem services under different development paths,formulating watershed ecosystem service regulation and decision-making plans is an important direction for future research.