Spatial and quantitative assessments of water yield services in watershed ecosystems are necessary for water resource management and improved water ecological protection. In this study, we used the InVEST model to estimate regional water yield in the Dongjiang Lake Basin in China. Moreover, we designed six scenarios to explore the impacts of climate and land use/land cover (LULC) changes on regional water yield and quantitatively determined the dominant mechanisms of water yield services. The results are expected to provide an important theoretical reference for future spatial planning and improvements of ecological service functions at the water source site. We found that (1) under the time series analysis, the water yield changes of the Dongjiang Lake Basin showed an initial decrease followed by an increase. Spatially, water yield also decreased from the lake area to the surrounding region. (2) Climate change exerted a more significant impact on water yield changes, contributing more than 98.26% to the water yield variability in the basin. In contrast, LULC had a much smaller influence, contributing only 1.74 %. (3) The spatial distribution pattern of water yield services in the watershed was more vulnerable to LULC changes. In particular, the expansion of built-up land is expected to increase the depth of regional water yield and alter its distribution, but it also increases the risk of waterlogging. Therefore, future development in the basin must consider the protection of ecological spaces and maintain the stability of the regional water yield function.

Catchments support the survival and development of humans in a region and investigating the mechanism of land-use changes and ecological responses in catchments is of great significance for improving watershed ecological service functions. Taking the Dongting Lake catchment as the study area, this study used spatial analysis, an ecosystem service value (ESV)-equivalent factor method, grid method, and other spatial analysis methods to explore land-use changes and the corresponding ecological service value response from 1990 to 2015, to provide an important theoretical reference for ecological service management, regional planning and ecological service function improvement in the Dongting Lake Basin. Our findings are as follows: (1) apart from a trend of notable expansion in construction land, the land-use types in the Dongting Lake catchment did not change significantly. (2) Grassland had the fastest transfer-out rate; forest land were cultivated land comparably transferred to each other with a larger area, where both were simultaneously and continuously transferred out as construction land; water areas, wetlands, and construction land were all transferred in, where construction land had the fastest transfer rate. (3) The total ESV of the watershed first increased and then decreased, but the overall change was small; spatially, the wetlands and water areas had a higher ESV, whereas construction land and cultivated land had lower ESVs. (4) Soil protection, gas exchange, climate regulation, biodiversity, and water conservation are always the main ecosystem service functions of a catchment, where the service function of the catchment ecosystem is greater than the productive function. The increase in construction land was the main factor for the increased differences between the spatial distributions of the soil, raw materials, biodiversity protection, and gas exchange.

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