Relationships among multiple ecosystem services in mountainous regions: A case study of the Gaoligong Mountains

Understanding the drivers and ecological implications of trade-offs and synergies among ecosystem services (ESs) is essential for sustainable mountain management. While previous studies have mapped ES relationships, the mechanisms underpinning their spatial heterogeneity in coupled human-natural systems remain underexplored. Here, we integrated gradient-based approaches to assess the distribution patterns of four ESs-water yield (WY), carbon storage (CS), net primary productivity (NPP), and habitat quality (HQ)-in the transboundary Gaoligong Mountains from 2001 to 2020. We found that: (1) Process-based services (WY-NPP) exhibited strong trade-offs, driven by climatic constraints and plantation expansion on southern slopes, where monoculture forests enhanced NPP but reduced infiltration capacity; (2) Synergies between structure-based services (CS-HQ) dominated mid-elevation forests, reflecting the dual role of conserved evergreen broadleaf forests in sequestering carbon and sustaining biodiversity through environmental conditions, complex canopy structures, and minimal human disturbance. Human activities disrupted natural synergies, as CS-HQ relationships shifted to trade-offs in high-intensity zones (e.g., cropland fragmentation and invasive species spread), highlighting conflicts between short-term provisioning and long-term regulating services; (3) Elevation gradients further shaped these dynamics: mid-elevation zones maintained balanced ecosystem service provision, while low-elevation agricultural areas experienced dual declines in net primary productivity (NPP) and habitat quality (HQ) due to cultivated land fragmentation, creating a trade-off between these services. This study contributes significantly to our understanding of ESs and intricate relationships within mountainous regions across temporal and spatial gradients. Our findings underscore the need to prioritize mid-elevation conservation corridors and adaptive agroforestry, providing valuable insights for decision-making processes in transboundary ecosystem conservation.