Spatial and Temporal Variations of Vegetation Water Content Using VOD and VPD in China During 2000–2016

Vegetation water content, characterized by vapor pressure deficit (VPD) and vegetation optical depth (VOD), can represent vegetation health in terrestrial ecosystems. In this study, using remote sensing Ku-band VOD and VPD, the spatiotemporal distribution assessment, Mann-Kendall trend analysis, seasonal trend decomposition, and correlation analysis and significance testing were conducted to investigate the spatiotemporal distribution patterns, seasonal variations and correlations of VPD and VOD across China from 2000 to 2016. And the correlation between climate factors (temperature and precipitation) with VOD and VPD was discussed. The results show the following: (1) The annual mean VPD in China predominantly ranged from 0 to 4 KPa, while the annual mean VOD were centered around 0 to 2 during 2000–2016. Spatially, the VOD peaked at 1–2 in southwest China. VPD have significant seasonal variations across China, with high VPD in the summer. (2) The VPD and VOD in most regions of China fluctuated and showed an upward trend from 2000 to 2016, with significantly increased VPD in northwest and southwest China. (3) On a monthly scale, regions where VOD positively correlated with VPD accounted for 89.69% of the total area of China. The proportion of areas with a significant positive correlation was 82.96%. The proportion of areas with a negative correlation was 10.31%, and the proportion of areas with a significant negative correlation was 5.41%. Annual VOD and VPD exhibited a positive correlation of 61.28% of China’s total territory. Among these, the area exhibiting a significant positive correlation made up 6.15%. The area demonstrating a negative correlation amounted to 38.72%, and the area with a significant negative correlation constituted 2.22%. This study can contribute to understanding vegetation water content dynamics across China, which is crucial for ecosystem sustainability in China.