Topographic-mediated climate-NPP relationships in subtropical mountain heterogeneity units.

Mountain ecosystems have experienced significant anthropogenic disturbances, resulting in severe degradation. Due to their intricate topography, climatic zonation, and spatial heterogeneity, the spatial and temporal evolution of net productivity in mountain ecosystems and the underlying driving factors remain unclear. This study focuses on the Southern Hilly Mountainous Belt of China (SHMB) to investigate the trends in net primary productivity (NPP) and its response mechanism from 2001 to 2020. The study employs Mann-Kendall trend test, Convergent Cross Mapping analysis, Pearson correlation analysis, and Geographical Detectors. The findings of this study are as follows: (1) The spatial distribution of NPP in the entire SHMB is significantly influenced by LULC (0.43 > q > 0.14, p < 0.005). (2) Human activities have significantly enhanced the carbon sequestration capacity in low-altitude areas (< 650 m) and gentle slope areas (< 16°). (3) Temperature, as the primary driving factor, has influenced the changes in NPP in the SHMB region over the 20 years. However, in the steep slope areas of the eastern and central regions of the SHMB, precipitation has significantly hindered the increase in NPP (-0.17 > q > -0.32, p < 0.05). In summary, human activities have significantly and positively driven the increase in NPP. However, in the central and eastern regions of SHMB, it is also necessary to guard against the ecological degradation caused by increased precipitation. These findings contribute to an enhanced understanding of the carbon cycle process crucial for achieving carbon neutrality, enhancing ecological functions, and studying global change.