Vegetation in terrestrial ecosystems as a carbon sink is a crucial factor in mitigating global warming and reaching carbon neutrality targets, although the drivers of net ecosystem productivity (NEP) under combined human and environmental pressures remain poorly understood. In this study, we analyzed the spatiotemporal evolution of NEP in the Horqin Sandy Land, China from 2000 to 2020, and observed the variation in NEP across different land use types. We further identified and quantified the effects of human activities, topographical features, climatic conditions, and soil properties on NEP through the application of structural equation modeling (SEM) and boosted regression trees (BRT). The results showed that the multi-year average NEP ranged from –137.79 to 461.96 g C/m 2 in the Horqin Sandy Land, with 88.21% of the area showing a significant increasing trend. Among different land use types, forestland exhibited the highest NEP values, followed by cropland, grassland, impervious land, and unused land. The NEP in carbon sink areas was primarily regulated by potential evapotranspiration (negatively correlated) and precipitation (positively correlated). Slope was identified as the most significant positive determinant in carbon source areas. Forestland exhibited climate–topography interactions driving NEP, whereas cropland and grassland relied on temperature; unused land and impervious land were susceptible to land use/cover change and human footprint. This study has significant implications for maintaining the carbon sink function and promoting ecological engineering programs that aim to enhance the capacity of terrestrial carbon sinks in the semi-arid agro-pastoral ecotone.
Xiaona et al. (Thu,) studied this question.