Integrating an InVEST-OPGD Framework to Decouple the Spatiotemporal Dynamics and Drivers of Water Conservation in the Tabu Agropastoral Ecotone

Water conservation (WC) is a critical regulating ecosystem service in agropastoral ecotones, yet its spatiotemporal dynamics and driving mechanisms in these vulnerable ecotones remain inadequately understood, hindering sustainable water resource management and ecosystem security. In this study, a novel framework is proposed that coupled the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model with an optimal parameter geodetector (OPGD) to assess the spatiotemporal heterogeneity in WC and its driving mechanism in the Tabu agropastoral ecotone from 2000–2022. Results revealed a pronounced south-to-north decreasing gradient in WC, with an insignificant increase of 0.04 mm/yr. The WC capacities across land use types ranked as follows: high-fractional vegetation cover (FVC) grassland > shrubland > medium-FVC grassland > low-FVC grassland > farmland > bare land > construction land. Hotspots were clustered in the southwest, whereas cold spots were clustered in the north. The areas of the two spots both decreased during 2000–2022, with cold spots disappearing entirely by 2022. Compared with anthropogenic factors (e.g., gross domestic product (GDP), population and the human footprint), natural factors (e.g., precipitation, elevation, temperature and evaporation) had greater influence on WC. Interactions between drivers predominantly exhibited bivariate enhancement, with the interaction between land use and land cover (LULC) and precipitation being the most significant (q_i: 0.33–0.67). A dual-pronged spatial strategy considering the optimization of the LULC layout and enhanced interaction is suggested in the ecological planning framework. This research provides critical support for water resource management and the maintenance of ecological security in ecotones. Moreover, it provides a transferable methodological tool for performing ecohydrological evaluations in other regions, particularly in the context of climate change and evolving land use trajectories.