###### Abstract  
Globally, forest ecosystems, especially subtropical forests, play a central role in biogeochemical cycles and climate regulation, demonstrating their irreplaceable function. The subtropical region of China, characterized by its unique forest ecosystem, complex terrain, climate heterogeneity, diverse vegetation types, and frequent human activities, underscores the importance of the in-depth study of its net primary productivity (NPP). This paper employs the eddy covariance-light use efficiency (EC-LUE) model to quantitatively estimate the gross primary productivity (GPP) of this region from 2001 to 2018, followed by an estimation of the actual net primary productivity (ANPP) using the carbon use efficiency (CUE). The results showed that over these 18 years, the annual average ANPP was 677.17 gC m\({}^{-2}\) a\({}^{-1}\), exhibiting an overall increasing trend, particularly in mountainous areas, reserves, and the cultivated lands of the northeastern plains, whereas a significant decrease was observed around the urban agglomerations on the southeast coast. Furthermore, the Thornthwaite memorial model was applied to calculate the potential net primary productivity (PNPP), and diverse scenarios were set to quantitatively evaluate the impact of climate change and human activities on the vegetation productivity in the study area. It was found that in areas where the ANPP increased, both human activities and climate change jointly influenced ANPP dynamics; in areas with a decreased ANPP, the impact of human activities was particularly significant. Additionally, the heterogeneous distribution of ANPP across different latitudinal gradients and the driving effects of various climatic factors were analyzed. Finally, a partial correlation analysis was used to examine the relationships between the temperature, precipitation, and ANPP. This study indicated that temperature and precipitation have a substantial impact on the growth and distribution of vegetation in the region, yet the extent of this influence shows considerable variation among different areas. This provides a robust scientific basis for further research and understanding of the carbon dynamics of subtropical forest ecosystems and their role in the global carbon cycle. net primary productivity (NPP); remote sensing; climate change; anthropogenic activities; elevation gradient  
ecosystems [5], are intricately linked with global biogeochemical cycles [6], and exert a certain regulatory influence on the climate [7; 8]. Subtropical forest ecosystems encompass a crucial segment of global vegetation diversity and are among the most productive ecosystems on Earth [3; 9]. On a global scale, climate warming and the rising concentration of carbon dioxide are among the primary characteristics of climate change. These changes have triggered a series of environmental issues, including ecosystem degradation, an increase in the frequency of extreme weather events, and land desertification. These environmental challenges typically occur concurrently with global warming, and their synergistic effects profoundly impact forest growth, mortality, and succession processes, thereby severely disrupting the carbon sequestration capabilities and other ecological functions of forests [10; 11; 12]. Concurrently, escalating human activities, such as uncontrolled resource extraction, human-induced forest fires, the invasion of alien species, and forest clearance due to population expansion, exert considerable adverse effects on forest ecosystems [13; 14]. Research on the global carbon cycle, especially in the context of climate change and human activities, has become a core issue in the field of environmental science [15; 16; 17; 18; 19; 20; 21]. Vegetation is a vital component of forests, playing a crucial role in the energy and material exchange processes within ecosystems [22].