Precipitation Concentration and Vegetation Dynamics in Guangdong Province: Spatial Heterogeneity and Implications

Precipitation concentration describes the uneven intra-annual distribution of rainfall and may regulate vegetation differently from total precipitation, yet its ecological effects remain poorly quantified in humid monsoon regions. Using multisource remote sensing and meteorological data for Guangdong Province from 2000 to 2022, we examined vegetation structural and functional responses to precipitation concentration through the precipitation concentration index (PCI), enhanced vegetation index (EVI), leaf area index (LAI), and solar-induced chlorophyll fluorescence (SIF). Sen’s slope, Mann–Kendall tests, and an eigenvector spatial filtering spatially varying coefficient(ESF-SVC) model were applied to characterize trends and spatially nonstationary climatic controls. The mean PCI was 13.72, indicating moderately concentrated annual rainfall; coastal areas had relatively uniform precipitation (PCI < 10), whereas inland areas showed stronger seasonality (PCI = 10 to 16). EVI, LAI, and SIF generally increased, but statistically significant declines occurred around the Pearl River and Rongjiang River estuaries. Monthly mean temperature, PCI, and solar radiation were the dominant controls, although their effects varied across precipitation gradients and ecosystem types. With increasing annual precipitation, the contribution of PCI weakened, while the negative effect of temperature strengthened and dominated within the 2,000- to 2,300-mm precipitation range. PCI contributed positively to LAI in forests (27.20%) and grasslands (32.62%), whereas SIF was more sensitive to combined temperature and radiation stress, highlighting differences between structural greenness and photosynthetic functioning. These results show that precipitation concentration influences vegetation through its interaction with thermal conditions, ecosystem characteristics, and human disturbance, and they support precipitation-gradient- and ecosystem-specific management strategies for humid monsoon landscapes.