Spatio-Temporal Evolution and Multidimensional Attribution of Ecosystem Services in Sanjiangyuan National Park

Elucidating the spatio-temporal evolution of ecosystem services (ESs) and their complex driving mechanisms is crucial for the restoration and differentiated management of integrated land-use systems in alpine national parks. Sanjiangyuan National Park is characterized by a forest–grassland–wetland mosaic, yet the ecological effects of long-term land-use transitions and their underlying drivers remain insufficiently understood. In this study, the InVEST model was used to evaluate the spatio-temporal dynamics of four key ESs: water conservation (WC), carbon storage (CS), habitat quality (HQ) and soil conservation (SC) from 1990 to 2020. Using the Geographical Detector Model (Geodetector), we quantitatively attributed the interactive effects of physiographical and socioeconomic factors on ES spatial differentiation. The results showed that (1) ESs generally exhibited positive changes over the past three decades, with WC and SC showing the greatest increases. Spatially, ESs exhibited a southeastward increasing gradient. (2) Single-factor detection showed that precipitation and Normalized Difference Vegetation Index (NDVI) were the main explanatory factors for WC, CS and HQ, while slope and precipitation were the main explanatory factors for SC; socioeconomic factors exerted weak but localized effects. (3) Pairwise interactions showed higher q-values than individual factors, primarily exhibiting bivariate enhancement and nonlinear enhancement, while the dominant interaction combinations varied among ESs and over time. This indicates that interactions among multiple physiographical and socioeconomic factors jointly shape the spatial patterns of alpine ES. This study deepens the understanding of ES dynamics in alpine national parks, providing scientific support for ecological conservation assessment, differentiated spatial management, and regional human–nature harmony.