Responses of forests, cultivated lands, and grasslands to climatic factors at a basin scale

Terrestrial ecosystems worldwide are largely governed by temperature and precipitation, and are expected to face transformation in response to warming. Growing evidence indicates an increasing drying trend in humid regions across China, while climate models project greater rainfall variability in these regions. Therefore, understanding how vegetation in humid regions responds to climatic variability is crucial for the sustainable management of ecosystems. In this study, using the Normalized Difference Vegetation Index (NDVI) and climate data, we investigated the vegetation variations and their responses to key climate factors (temperature, precipitation, wind, and solar radiation) in the humid East River basin (ERb) from 2000 to 2018. Results showed that (i) NDVI increased significantly (0.006/yr), indicating a greening effect in the ERb; (ii) temperature was the most important factor driving vegetation dynamics, especially for cultivated lands; (iii) precipitation benefited only cultivated lands but not forests and grasslands; (iv) solar radiation was more pronounced in benefiting forests and grasslands, while wind has only a slight positive correlation with cultivated land during the wet season. Forests consistently had the highest NDVI values in both wet (peak: 0.74 in 2017) and dry seasons (peak: 0.71 in 2017), followed by grasslands and cultivated lands. These findings demonstrate sustained vegetation growth, with forests being the most robust growth and dry-season dynamics driving the strongest fluctuations. This study strengthens our understanding of the responses of different vegetation types to climate in humid regions, which will benefit agricultural management under climate change and provide a reference for other humid regions.