| As one of the important ecosystem service functions,water yield service is continuously subjected to the interference and influence of climate change and human activities.Climate and land use landscape pattern changes,as the main ways,have extensive and far-reaching impacts on water yield service.Therefore,it is of great practical significance to accurately assess the effects of climate and land use landscape pattern changes on water yield service functions.Taking Yunnan Province as an example,the temporal and spatial distribution characteristics of water yield in Yunnan Province during 1990-2020 were simulated based on the InVEST model,and the spatial differentiation characteristics and rules of the effects of climate factors and landscape pattern factors on water yield were analyzed by the geographically weighted regression model(GWR).Finally,in the context of global warming and territorial space planning,Based on future climate model scenario data(sustainable path(ssp126),intermediate path(ssp245),regional competition path(ssp370),fossil fuel dominated development path(ssp585))and land use scenario data(natural development scenario(nds),urban development scenario(uds),cropland protection scenario(cps),ecological protection scenario(eps),quantitatively evaluated the water yield under different climate and land use change combination scenarios in Yunnan Province from 2021 to 2050 by using InVEST model,and revealed its response mechanism to climate and land use landscape pattern changes.The main research results are as follows:(1)The climate change in Yunnan Province from 1990 to 2020 was mainly warm and dry.Precipitation decreased significantly at the rate of 44.46 mm/10 a.Temperature and potential evapotranspiration increased significantly at the rate of 0.42 ℃/10 a and31.05 mm/10 a,respectively.Compared with the base period(1990-2020),the precipitation in Yunnan Province will decrease by 5.52%～13.92% under the four climate scenarios from 2021-2050,the temperature will increase by 1.78%～3.26%,the potential evapotranspiration will increase by 28.61%～30.06%.(2)In the past 30 years,there have been significant changes in land use in Yunnan Province.The area of cropland,shrubs,permanent ice and snow,and wasteland has decreased first and then increased,while the area of forest land,impervious surfaces,water bodies,and wetlands has increased.In the future 30 years,different land use scenarios will result in different changes in quantity and space for each land type.Cropland,forest,grassland,and impervious surfaces are the main land types for land use transfer in Yunnan Province.Under the nds and uds,the impervious surface area expands rapidly,and cropland,grassland,and other production-ecological land become the main sources for this type of land transfer.Under the cps,the cropland area has significantly increased,effectively ensuring the quantity of cropland,but a large amount of ecological land has been sacrificed.Under the eps,the expansion of impervious surfaces is significantly reduced,and the area of ecological land is effectively improved.However,in order to meet the requirements of economic development,a large amount of cropland is converted to impervious surfaces,and cropland and other production land are subject to certain restrictions.(3)From 1990 to 2020,the water yield in Yunnan Province showed a decline trend,with a decline rate of 27.2%.In terms of spatial distribution,the overall pattern is decreasing from northwest,west and southwest to central and eastern areas.The highvalue area of water yield is concentrated in the south of the Yuanjiang River,the north of the Nujiang River,the middle and south of the Irrawaddy River,while the low-value area is concentrated in the northwest of the Jinsha River.Due to the influence of climate and changes in land use landscape patterns,the water yield in Yunnan Province will increase in only four scenarios,namely ssp585-nds,ssp585-uds,ssp585-cps,and ssp585-eps in 2035,while the water yield of other scenarios will decline.(4)Climate and land use change affect the temporal and spatial variation of water yield in Yunnan Province.From the perspective of land use change,different land use scenarios caused different changes in water yield when climate scenarios were the same.However,in 2035 and 2050,the water yield in Yunnan Province will be the highest under the cropland protection scenario,which means that the implementation of strict cropland protection will lead to more water yield,which is a prerequisite for the occurrence of potential flood risks,especially in areas with rapid urbanization.From the perspective of climate change: when land use scenarios are the same,different climate scenarios cause different changes in water yield,and the scenario with high precipitation also has higher water yield.However,with the significant decrease of precipitation in different climate scenarios in the future,the water yield will also show a significant decrease trend,which means that more severe drought may occur.(5)The influence of climate change on water yield is greater than that of land use landscape pattern change.In 1990,the water yield of Yunnan Province was dominated by precipitation,accounting for 53.20% of the area,followed by the actual evapotranspiration(43.23%).The regions dominated by precipitation were mainly distributed to the west of the Yunling Yuanjiang line(Irrawaddy River,Nujiang River,Lancang River,Yuanjiang River),and the regions dominated by the actual evapotranspiration were mainly distributed to the east of the Yunling Yuanjiang line(Jinsha River,the Pearl River).In 2005 and 2020,the water yield of Yunnan Province was dominated by precipitation,with the area accounting for 97.86% and 98.28%respectively.The area of other factors was relatively small and could be ignored.(6)Except for ssp370-nds,ssp370-uds,ssp370-cps and ssp370-eps in 2050,the water yield of Yunnan Province is dominated by precipitation in the largest range,with the area ratio ranging from 95.81% to 97.53%.The area dominated by temperature,potential evapotranspiration,actual evapotranspiration,COHESION,PD,SPLIT,LSI and other factors is less than 5%,and is mainly distributed in the southwest of the Irrawaddy River,the southeast of the Lancang River,and the southeast of the Yuanjiang River.In general,precipitation is the main driving force affecting the spatial heterogeneity of water yield in Yunnan Province. |
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