| Maintaining ecosystem health is a fundamental guarantee for sustainable development of watersheds,and revealing the level of ecosystem health in watersheds has important practical significance for the formulation of watershed ecological protection policies.The Yellow River Basin occupies an important position in China’s socio-economic development and ecological protection.As a typical ecologically fragile area and climate-sensitive area in China,the ecosystem health of the Yellow River Basin is related to the construction of China’s ecosystem security pattern.It is important to analyze the ecosystem health level of the Yellow River Basin in the context of global climate change and economic globalization.In the context of the strategic demand for high-quality development of the Yellow River basin,how to achieve a "win-win" situation between socio-economic development and ecological protection in the Yellow River basin is a pressing issue.Therefore,this study takes the counties(involving 86 municipalities and 726 counties)flowing through the main and tributaries of the Yellow River as the study area,and firstly quantifies the intensity of human activities in the Yellow River basin from five perspectives: land use,economic development,population concentration,pollution emission,and policy management.Secondly,based on the traditional Vitality-Organization-Resilience(VOR)model,an ecosystem health assessment system based on the framework of ecosystem "physical health-functional services-environmental quality" was established in the Yellow River Basin,which finally revealed the driving mechanisms of climate change and human activities on ecosystem health in the Yellow River Basin,and further The study further delineated the ecological health zones of the Yellow River Basin and proposed ecological protection strategies for different ecological health zones.The main research findings are as follows.(1)In terms of climate change characteristics,the overall climate change in the middle reaches of the Yellow River from 2000 to 2020 shows a warm and wet trend,while the climate change in the upper and lower reaches of the Yellow River shows a warm and dry trend.The annual average temperature,rainfall,relative humidity and sunshine hours in the Yellow River basin have significant spatial variability,with precipitation and relative humidity gradually increasing from north to south,and sunshine hours decreasing in a stepwise manner from north to south,while temperature is spatially distributed as "high in the west and low in the east".Regional differences in climate conditions are the key to spatial heterogeneity of ecosystem health.(2)The intensity of human activities in the Yellow River basin increased by 77.78% from2000 to 2020,with an overall spatial distribution of "high in the east and low in the west",and the percentage of areas with an increasing trend is 93.05%;the growth rate of human activities intensity is generally upstream > midstream > downstream,with the Yellow River In the past 20 years,the intensity of human activities in the Yellow River basin has shifted from Linfen City,Shanxi Province to Yan’an City,Shaanxi Province,with an overall shift of 152.58 km to the northwest.(3)From 2000 to 2020,the overall level of ecosystem health in the Yellow River Basin has improved,with more than 50% of the areas in the Yellow River Basin showing overall improvement in ecosystem physical health,comprehensive service functions and ecological environment quality,and the level of ecosystem health in the Yellow River Basin is mainly "good" and "excellent".Ecosystem health in the Yellow River Basin is mainly "good" and "excellent".The spatial and temporal evolution of ecosystem health and its components vary significantly in the upper,middle and lower reaches of the Yellow River.The ecosystem health in the lower reaches of the Yellow River is generally higher than that in the middle and upper reaches from 2000 to 2020,and the ecosystem health in the middle and upper reaches of the Yellow River has shown an increasing trend in the past 20 years,while the ecosystem health in the lower reaches has shown a decreasing trend.(4)The relationship between human activities and climate change and ecosystem health has a scale effect,and the increase of the study scale weakens the degree of influence of most human activities and enhances the degree of influence of climate factors;rainfall,sunshine hours and relative humidity are the main factors contributing to the spatial heterogeneity of ecosystem health in the Yellow River basin;72.95% of the ecosystem health in the Yellow River basin is driven by both human activities and Ecosystem health is driven by both human activities and climate change in 72.95% of the Yellow River Basin,with 49.30% of the areas showing positive effects and 23.65% showing negative effects;the response mechanisms of ecosystem health to the thresholds of human activities and climate change factors are different,and the effects of human activities and climate change on ecosystem health have significant spatial and temporal non-stationarity.(5)The Yellow River Basin mainly includes four ecological service function areas,four ecosystem health areas,eight ecosystem health classes and 18 ecosystem health subclasses.Using the SOM model,we finally identified four major ecological function areas in the Yellow River Basin,among which carbon sequestration and oxygen release is the main ecological service cluster in the Yellow River Basin,accounting for 46.14% of the area of the Yellow River Basin;the RDA model was used to screen the human activities and climate change factors that can characterize the ecosystem health in the Yellow River Basin,and based on the K-mean clustering delineation,we finally divided four typical ecological health areas,and according to the different ecological Based on the ecological health categories in different ecological zones,eight subcategories of ecosystem health were finally classified,and further combined with the topographic and geomorphological characteristics of the region,18 subcategories of ecosystem health in the Yellow River Basin were formed,and key measures to improve ecosystem health in the region were proposed based on the ecosystem services and ecological health characteristics in each subcategory. |
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