Spatiotemporal dynamics and trade-off/synergy relationships of grassland ecosystem services in karst regions

Karst regions are characterized by ecological fragility and severe rocky desertification, where grassland ecosystems play a critically important role in maintaining ecological security. However, integrated assessments of multiple ecosystem services (ESs) and their interactions in karst grasslands remain limited, constraining effective ecosystem management and sustainable development. This study conducted a comprehensive analysis of four key ecosystem services—soil retention, water retention, biodiversity, and carbon sequestration—across Guizhou Province from 2000 to 2020, examining their spatiotemporal patterns, driving factors, and trade-off or synergy relationships. The results revealed that: (1) Over the past two decades, grassland ecosystems in Guizhou Province exhibited average values of 18.900 t hm^-2 yr^-1 for soil retention, 127.029 m³ hm^-2 yr^-1 for water retention, 0.011 (generally important) for the biodiversity index, and 4.495 t hm^-2 yr^-1 for carbon sequestration. High-value areas for most ESs were concentrated in southern Guizhou, while low-value areas were predominantly distributed in the western region. Temporally, soil retention, water retention, and carbon sequestration showed increasing or stable trends with interannual fluctuations, whereas the biodiversity index declined over the study period. (2) Temperature emerged as the primary factor influencing grassland ESs, followed by rainfall; the interaction between these two factors significantly enhanced explanatory power, with temperature exhibiting strong correlations with both altitude and GDP. (3) With the exception of a predominantly trade-off relationship between soil retention and other functions, all ecosystem services exhibited significant synergistic relationships. To promote sustainable development of regional grassland ecosystems, land planning processes must fully consider the interconnections among ESs, striving to minimize trade-offs and foster synergistic outcomes. This study provides new insights into the integrated dynamics and interactions of ecosystem services in karst grasslands, offering a scientific basis for optimizing ecosystem management and advancing sustainable regional development.