Effects of climate change and human activities on vegetation net primary productivity: a case study of Henan Province, China

Abstract

Net primary productivity (NPP) is a key indicator of the carbon-sink capacity of terrestrial ecosystems. Annual MODIS NPP data from 2001 to 2024 were used to characterize the spatiotemporal dynamics, stability, and future trajectories of NPP in Henan Province using Theil-Sen trend analysis, the Mann-Kendall test, the coefficient of variation, the Hurst exponent, and the gravity-center model. Partial derivative analysis was then applied to quantify the relative contributions of climatic factors (temperature, precipitation, and solar radiation) and human activities to observed NPP changes. Results indicate that, over the 24-year period, NPP increased significantly at a rate of 4.43 g C·m -2 ·a −1 ( P < 0.01), with a multiyear mean of 486.88 g C·m -2 ·a −1 . NPP varied substantially among land-use types, with the highest values in woodland, followed by grassland and farmland, and the lowest values in barren land. Spatially, high NPP values occurred in western and southern Henan, whereas low values occurred in eastern and northern Henan. NPP increased across 94.70% of the vegetated area, with significant increases (64.41%) concentrated in the central-western and southern regions; areas of decline (3.14%) were mainly distributed along the Beijing-Guangzhou and Lianyungang-Lanzhou railways corridors. NPP was generally stable over time (mean CV = 0.14); however, a mean Hurst exponent of 0.46 suggested that 69.07% of the region would exhibit anti-persistence characteristics. The NPP gravity center shifted 4.58 km northwestward during the study period. Climate change and human activities contributed 43.19% and 56.81% to NPP changes, respectively. Human activities were the primary driver of vegetation improvement (57.85%), whereas climate change dominated vegetation degradation (67.82%). Although ecological restoration and agricultural modernization have partly offset the adverse effects of climate change, a substantial risk of future degradation remains. Targeted adaptive management is needed in high-risk areas to safeguard regional carbon sinks and sustain ecosystem services.