Evaluate Water Yield and Soil Conservation and Their Environmental Gradient Effects in Fujian Province in South China Based on InVEST and Geodetector Models

Fujian Province is an important soil and water conservation region in hilly South China. However, there has been limited attention paid to the assessment of water production and soil conservation at the provincial level, and the distribution patterns of ecosystem services under different environmental gradients in hilly regions have not been revealed. This study evaluated the spatiotemporal characteristics of water yield and soil conservation based on the InVEST model in 2000, 2010, and 2020, and explored their differences under six environmental gradients: elevation, slope, terrain position index, geomorphy, LULC, and NDVI. The results and statistics of the InVEST model showed significant spatial differentiation and temporal change in water yield; the distribution and changes in water yield and soil conservation both exhibited obvious clustering characteristics of cold and hot spots (low and high values); and the differences in distribution and change in water yield in different cities were higher than those in soil conservation. The distribution index and Geodetector showed that there were spatiotemporal differences in distribution and change characteristics of water yield and soil retention in different environmental gradients; the distribution and change differences in water yield were generally lower than those of soil conservation and the degree of distribution and change in water yield and soil conservation were generally more sensitive to the response of terrain factors (slope, TPI, and DEM). The high-value important regions of water yield and soil conservation were 1000 to 2160 m for DEM, 25° to 70.2° for slope, 0.81 to 1.42 for TPI, medium mountain for geomorphy, forest land for LULC, and 0.9 to 0.92 for NDVI, which indicates mountainous regions with high altitude, steep slopes, significant terrain changes, and high forest vegetation coverage. This study indicates that ecosystem services exhibit spatiotemporal differences in distributions across different environmental gradients, and attention should be paid to adapting to local conditions in ecological environment development.