| Climate change has been an important factor driving the continuous change of ecosystems,and land use change under human interference is also a key factor affecting the structure,function and dynamics of ecosystem services.At present,in policy decisions involving land use and ecological construction,it is very important to accurately evaluate the characteristics of ecosystem services and combine with the needs of different stakeholders to maximize the ecosystem services and realize the sustainable development of "nature economy" for ecosystem management,which has become a hot and difficult point in geography,ecology and other research.The upper reaches of Han River is a typical mountain basin,which is located in Qinba Mountainous Region.Water conservation and ecological barrier play an important role.Meanwhile,its ecological environment is sensitive and soil erosion is serious.As the water source of the Central Line Project of South-to-North Water Diversion,since the implementation of the project,the water resources in Han River Basin have been greatly reduced,water pollution has led to the deterioration of water quality,which has an important impact on the surrounding environment,the middle and lower reaches of the environment and the water security of the cities that need water.Therefore,taking the upper reaches of the Han River as the research object,based on multi-source data,using GIS spatial analysis,scenario analysis,and InVEST model applications as the main technical services of ecosystem services,we assessed four typical ecosystem services:soil and water conservation,biodiversity maintenance,and carbon storage,and revealed the dynamics of ecosystem services in this region,reveals the ecosystem of the study area in 2018 Service status(baseline scenario),and identify ecosystem service multi-functional area(EMSA)by the Gi*statistical method.In addition,taking into account the needs of various interests and the suitability of land use,simulate and optimize the land use,and set up the urban natural development scenario,the conversion of farmland to forest scenario and the land use optimization scenario scheme.By combining InVEST model and scenario analysis,the paper evaluates multiple ecosystem service functions under three scenarios,explores multiple ecosystem service changes under multi scenario scenarios by using correlation analysis method,ecosystem change index(ESCI)and ecosystem service trade-off/synergy index(ESTD),explores the temporal and spatial characteristics of ecosystem service trade-off/synergy,and seek a sustainable development approach of multiple ecosystem services with less trade-off,more synergy and maximization of comprehensive benefits.The main conclusions are as follows:(1)In the 2018 baseline scenario,water conservation shows a trend of "high in the South and low in the north".The water conservation advantages of Lan River,Zhu River and other basins in the south are greater than those of the northern rivers(the northern slope of Ta-pa Mountains is stronger than the southern slope of Qinling Mountain);the median value of soil conservation in the basin is widely distributed,and soil erosion shows a trend of "northwest southeast" gradually increasing.In the southeast,the degree of soil erosion is the most severe,and the soil conservation is also high,the situation is complex;the biodiversity and carbon storage are distributed in the trend of "high in the northwest,low in the middle and South".The average factor value of the overall habitat quality is 0.66,especially in Qinling Mountains,which shows a good habitat function.There are many rare animals and plants,and the carbon storage function is strong,especially in the northwest.(2)Multi functional area of ecosystem services provides a variety of ecosystem services,which is an efficient area of ecological management,accounting for 25.05%of the total area,mainly located in the northwest and south edge of the study area,while the middle and northeast are small scattered.According to the knowledge of ecosystem service trade-off/synergies relationship,when the two ecosystem services are synergies,one service hot spot is similar to the other in spatial distribution;on the contrary,one service hot spot in the trade-off relationship is roughly another service cold spot.(3)Compared with the three scenarios,the spatial distribution trend of ecosystem services roughly converged to the baseline scenario in 2018(except for biodiversity and carbon storage),and the total amount of substances in ecosystem services changed significantly.At the same time,combining the distribution of gain and loss,we can see that the positive effects of three scenarios on the ecological environment are as follows:the scenario of returning farmland to forest>the scenario of land use optimization>the scenario of urban natural development.(4)In the past 30 years,biodiversity and carbon storage in the study area are highly collaborative,water conservation and biodiversity,carbon storage are basically moderate or low trade-off,and other ecosystem services are not significantly correlated.(5)From the correlation,the urban natural development scenario and the conversion scenario basically conform to the historical law of 1990-2018.The difference is that the trade-off between ecosystem services in the conversion scenario is less than that in the urban natural development scenario,and the trade-off under both scenarios is greater than the historical law.In the land use optimization scenario,biodiversity and carbon storage are highly collaborative,there is no obvious trade-off relationship between other ecosystem services,and the competition or conflict relationship is eased.(6)Spatially,the dominant relationship type under the three scenarios is the synergistic effect between biodiversity and carbon storage,while in the urban natural development scenario.the secondary dominant relationship is the trade-off between water conservation and biodiversity,and the light trade-off between water conservation and soil conservation;In the scenario of returning farmland to forest,the area of tradeoff relationship between water conservation and other three typical ecosystem services is larger than the collaborative area.Soil conservation,biodiversity and carbon storage show a collaborative relationship,which is slightly stronger than the collaborative distribution and degree in the urban natural development scenario;In the land use optimization scenario,there is no clear trade-off or collaboration relationship between the two ecosystem service pairs,and the trade-off is weakened,while the local collaborative relationship is enhanced.(7)According to the comprehensive analysis,the ecosystem services capacity is weakened under the natural development scenario of cities and towns;The spatial synergy between soil conservation and carbon storage is enhanced and the quality of materials is increased in the scenario of returning farmland to forest,which is dominant in the ecological protection;The land use optimization scenario can basically maintain the ecosystem service and weaken its trade-off and competition relationship on the basis of satisfying human construction and production,which is an alternative and effective way to achieve the win-win goal of "nature society". |
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