Effects of Climate and Land Cover on the Relationship of Satellite Derived Vegetation Water Content and Greenness

The relationship between vegetation water content and greenness has been quantified for various vegetation types over a range of contrasting climate regimes. NDVI and vegetation water content (VegWC) are derived from MODIS and AMSR, respectively. Three study areas were selected: North America Monsoon System (NAMS) region, International H₂O Project (IHOP) region, and a region in Georgia. Both NDVI and VegWC are higher in the more mesic IHOP region than in the arid NAMS region. Although NDVI is even higher in the humid Tifton region, VegWC does not also increase. The VWC of natural ecosystems exhibits greater spatial and temporal variability than in crop regions. Overall, the differences in VegWC between regions and land cover types are small compared to that for greenness. This observation is reasonable given the adaptations of plants to cope with the soil water limitations that are common in dry climates.