Study on Spatiotemporal Differentiation of Vegetation NPP and Its Influencing Factors in the Huaihe River Basin Since 2000

Under the dual stress of climate change and intensive human activities, vegetation dynamics in the Huaihe River Basin, a typical north–south climatic transition zone in China, merit close attention. Net Primary Productivity (NPP) serves as a core metric for characterizing ecosystem carbon-sink capacity and vegetation growth status. Elucidating its spatiotemporal patterns and driving factors is of great significance for regional ecological conservation and adaptive management. Taking the Huaihe River Basin as the study area, this study utilizes MOD17A3HGF NPP datasets and multi-source geospatial data spanning 2000–2024. Integrating trend analysis, the Hurst exponent, residual analysis, and the Geodetector model, this work aims to reveal the spatiotemporal evolution and prospective change trends of vegetation NPP, and to quantitatively identify the independent and interactive effects of climate, topography, and human activities on NPP spatial differentiation. The results show that: (1) Temporally, vegetation NPP exhibits an overall fluctuating upward trend, increasing from 370 gC·m−2·yr−1 to 475 gC·m−2·yr−1, with a multi-year average of 422.9 gC·m−2·yr−1. The period 2013–2014 marks a prominent inflection point for NPP growth. Spatially, NPP follows a distribution pattern of high values in the southeast and low values in the northwest. (2) NPP shows an increasing trend across 94.09% of the basin. Meanwhile, 86.27% of the study area is characterised by anti-persistence, i.e., historical vegetation improvement accompanied by prospective degradation risks, which poses substantial challenges to ecosystem resilience. (3) Climatically, precipitation exhibits strong positive correlations with NPP, followed by temperature. Topographically, the maximum NPP occurs within the elevation band of 500–1000 m and the slope gradient range of 25–35°. Human activities exert positive promotional effects over most parts of the basin, presenting a spatial gradient with high contributions in western mountainous regions, moderate contributions in eastern plains, and low contributions around urban peripheries. (4) Precipitation, elevation, and geomorphic type are the dominant driving factors. Most pairwise factor interactions produce enhanced explanatory power, among which the interaction between elevation and precipitation yields the highest explanatory capacity. This coupling reflects topographic modulation of hydrothermal conditions and the spatial redistribution of precipitation, which creates divergent water availability and vegetation habitats across terrain units. Population density exhibits weak explanatory power when acting independently; nevertheless, its explanatory capacity rises substantially after interacting with precipitation and elevation. This finding indicates that anthropogenic impacts on vegetation are embedded within specific natural environmental contexts.