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Since 2011, the Chinese government has been implementing a series of comprehensive rock desertification control projects. Concurrently, the relevant ecosystem service functions have been changing. However, few studies have quantitatively evaluated the variation of each ecosystem service function and its driving factors; moreover, the trade-off and synergistic relationships must be further explored. Therefore, the present study used a Soil and Water Assessment Tool (SWAT) model to stimulate three ecosystem service functions of the surface/underground runoff and surface sediment yield of Dabang River (a typical karst basin in Southwest China); the driving factors of ecosystem service variation were examined using geographic detectors; and a Spearman correlation analysis was performed to explore the trade-off and synergy between ecosystem services. This study revealed the following results: (1) The determination coefficient (R2) and Nash efficiency coefficient (NS) are>0.5 during the calibration and validation periods; therefore, they meet the model evaluation requirements, verifying the applicability of the SWAT model for ecological service function evaluation in karst areas. (2) Surface/underground runoff decreased by approximately 64% and 66.53% and surface sediment yield decreased by 25.89% in the study area from 2010 to 2018. (3) The geographic detector results revealed significantly higher explanatory power for two-factor detection than for single-factor detection for the variation of ecosystem services. Changes in various ecosystem services are closely related to rainfall reduction, land use changes, and the succession of rocky desertification. (4) Trade-off relationships exist between surface and underground runoff and between underground runoff and surface sediment yield; a synergistic relationship exists between surface runoff and surface sediment yield. The results provide a theoretical reference for the control of rocky desertification/soil erosion as well as for ecological protection and restoration work in karst areas of Southwest China.
Jiang et al. (Fri,) studied this question.