Spatio-temporal Variability And Driving Mechanisms Of Ecosystem Services Trade-offs At The Watershed Scale

Ecosystem services are one of the key issues in integrated watershed management and sustainable development.Clarifying the spatial and temporal characteristics of basin ecosystem services and their interrelationships is a prerequisite for analysing the trade-offs between ecosystem services and improving the quality and benefits of ecosystem services mentioned,especially for basins with poor natural endowments and severe human disturbances.This paper takes the Haihe River basin,where human-land relations are tense,as the study area,and analyses the spatial and temporal evolution of ecosystem patterns in the basin between 1980 and 2018.The main drivers of spatial and temporal variation in ecosystem services and trade-offs are clarified,the major mechanisms of spatial-temporal variation in the trade-offs of ecosystem services in the basin are investigated.The main results and conclusions are as follows.(1)During the period 1980-2018,land use changes in the Haihe River Basin were characterised by a loss of cropland,an expansion of land for construction and a decrease followed by an increase in forest land.The proportion of cropland area decreased by3.12%;the proportion of construction land increased by 3.77%;the proportion of forests decreased by 0.15% between 1980 and 2000,and increased by 0.26% between 2000 and 2018 due to the influence of ecological protection policies such as returning farmland to forest.The transformation between land use types mainly occurred between forests and grassland,cropland and urban construction land,with the flow of cropland in the plains dominated by construction land due to the rapid urbanisation and the implementation of ecological protection policies,and the flow of cropland in the mountains dominated by construction land before 2000 and transformed into forests and grassland and construction land after 2000.(2)During the period 1980-2018,the supply services in the Haihe River Basin maintained a trend of annual increases,with food production increasing by 136.4% and water production services by 6.6%;regulating services showed fluctuating increases,with sand prevention increasing by 16.88% and soil retention increasing by 0.3%;while supporting services showed a trend of annual decreases,decreasing by 2.5%.Changes in ecosystem services in the mountainous sub-basins of the Haihe River Basin were mainly influenced by natural background conditions before 2000,and by a combination of changes in forest and grassland brought about by ecological policies and natural background conditions after 2000;changes in ecosystem services in the sub-basins of the plain areas were mainly influenced by a combination of changes in ecosystem patterns brought about by urbanisation and natural background.(3)The trade-off between food supply and other services in the Hai River basin showed fluctuations in the mountainous areas during the study period,with the largest trade-off between food supply and habitat quality,increasing from 0.32 to 0.34 between1980 and 2000,before decreasing to 0.33 in 2018.In the plains region there is a trend towards increased trade-offs,with the greatest trade-off between food supply and soil conservation,increasing from 0.28 to 0.34 between 1980 and 2018.The trade-off between water production services,regulating services and habitat quality does not change much over time in mountainous areas;in plain areas it tends to increase over time,with the largest trade-off between water production and soil conservation,increasing from 0.25 to 0.28 over the period 1980-2018.The trade-offs between regulating services and habitat quality,and between regulating services,were all less than 0.2.(4)During the study period,the more variable trade-offs in the mountainous areas of the Haihe basin were concentrated between regulating services(soil conservation,sand prevention)and supply services(food production)and supporting services(habitat quality),and the plains area is concentrated within the supply services(food production and water yield.The main influencing factors in mountainous areas are changes in forest and grassland brought by ecological projects,changes in cropland brought by policies such as the grain for green project and natural background conditions.The main influencing factors in the plains region are the changes in arable land and construction land brought about by urbanisation and the natural background conditions.The results of this study demonstrate the need for zoning and dynamic adjustment of management measures in watershed ecosystems,providing useful information for the conservation and management of watershed ecosystems to effectively enhance ecosystem services and reduce trade-offs between ecosystem services to maximise benefits.