Abstract: Carbon use efficiency (CUE) and water use efficiency (WUE) of vegetation are critical variables for characterizing the coupled carbon-water cycling in terrestrial ecosystems. Based on satellite remote sensing and ground observation data, we used linear regression analysis, stability analysis, trend analysis, Mann-Kendall test, Hurst index, and partial correlation analysis to investigate the spatiotemporal variations of vegetation CUE and WUE in northern Guangdong from 2000 to 2024 and their responses to climatic factors, aiming to provide a theoretical basis for understanding the coupling mechanisms of carbon-water cycling in this region. The results showed that: (1) During 2000-2024, the mean CUE and WUE in northern Guangdong were 0.509 and 0.913 g C·m^-2·mm^-1, respectively, exhibiting a spatial pattern of lower values in the northwest and higher values in the southeast. CUE displayed a significant decreasing trend, whereas the decline in WUE was statistically insignificant. (2) Stability analysis indicated predominantly low or relatively low fluctuations in both CUE and WUE across most areas. (3) CUE degradation was widespread. In contrast, improvement areas exceeded degradation areas for WUE. Persistence analysis suggested that decreasing CUE trends would continue in most regions, while projected increases in WUE would exceed decreases. (4) Temperature exerted stronger control over CUE than precipitation and drought, whereas precipitation dominated WUE variation. Increasing temperatures suppressed CUE, while rising precipitation reduced WUE. Drought tended to enhance both CUE and WUE.

Key words: carbon use efficiency, water use efficiency, spatiotemporal distribution, climatic factor