Abstract: Water yield is an important ecosystem service. It is the key to maintain ecological security and sustainable development to accurately grasp the spatial heterogeneity characteristics and identify the key driving factors of water yield in different regions. Taking Yunnan Province with significant geospatial heterogeneity as the research area, we used InVEST model to simulate the temporal and spatial variations of water yield in Yunnan Province from 1992 to 2019. The spatial characteristics of driving factors, such as climate, vegetation, soil, terrain, land use, on water yield service were analyzed through Geodetector. The results showed that water yield of Yunnan Province showed a fluctuating trend of increasing at first and decreasing later from 1992 to 2019, with a similar spatial distribution pattern in each year, and an overall trend of gradually decreasing from northwest, west and southwest to central and east. Climatic factors (precipitation and actual evapotranspiration) were the main driving factors leading to spatial differentiation of water yield. In different watershed divisions, the impact of each driving factor on water yield had significant spatial heterogeneity: the watersheds dominated by precipitation were mainly distributed in the west of Yunling-Yuanjiang line, the Irrawaddy River, the upper reaches of Nujiang River, the lower reaches of Nujiang River, the upper reaches of Lancang River, the upper reaches of Jinsha River, Yuanjiang River and Lixian River areas. As for the east of Yunling-Yuanjiang line, in karst landform areas (Nanguang River, Chishui River, Wujiang River, Youjiang River and Panlong River) and the lower reaches of Jinsha River with high population density and shortage of cultivated land, actual evapotranspiration and land use type were the leading factors controlling the spatial pattern of water yield. The results could provide a reference for water resources management policy and ecological civilization construction in Yunnan Province, with a certain guiding significance to promote the optimization and sustainable development of ecosystem services in complex plateau-mountain area.

Key words: water yield service, InVEST model, GeoDetector, spatial heterogeneity, Yunnan Province