Monitoring grassland degradation under grazing and climate stress in Hustai National Park using NDVI analysis

Grasslands cover nearly one-third of Earth's terrestrial surface and play a critical role in global carbon and nutrient cycling; however, those in semi-arid regions are particularly vulnerable to climate variability and local disturbances. Disentangling the relative influences of climatic drivers and local disturbances remains a major ecological challenge. This study investigated relative influences of climate drivers and local disturbances on grassland dynamics in Hustai National Park (HNP), which serves as a critical habitat for the Przewalski's horse, through an integrated approach combining satellite-derived normalized difference vegetation index (NDVI), field-based biomass measurements, and soil–plant nutrient analyses. The park exhibited sensitivity to climate variability, particularly rising temperatures. A negative correlation between land surface temperature and NDVI indicated increasing climate stress across the region. Results showed that a 1 °C increase in temperature reduced net primary production by 14.07 g C m−2, while a 1 mm increase in precipitation increased net primary production by 1.28 g C m−2 during summer. Vegetation analysis further revealed a shift from subshrubs/shrubs to grasses/forbs in HNP, suggesting potential land degradation associated with elevated herbivore activity, supported by higher dung cover and standing dead biomass. Soil–plant nutrient relationships demonstrated species-specific responses, with Stipa krylovii showing greater temperature sensitivity, while Artemisia frigida exhibited higher uptake of major mineral elements. These differences may arise from herbivore preference for palatable species or intrinsic differences in nutrient acquisition strategies between monocots and dicots. These findings provide important baseline insights into climate–grazing interactions and offer guidance for sustainable grassland management and conservation in semi-arid ecosystems.