Collected data goes on the Web. Yet the usefulness of any such satellite information is fundamentally determined by an understanding of how ground vegetation conditions correspond to satellite estimates. Student observations do show that dates of leaf budburst correspond remarkably well with satellite growing season estimates. Slope of the relationship was 0.20 with an r2 of 0.70. NDVIbud versus prediction error in days.
Horizontal line shows zero error.
The data strongly suggest that over many sites in the continental United States, onset of greenness occurs at approximately the initiation of upper-canopy growth in the deciduous broad leaf forest biome. Lower-canopy vegetation activity is therefore highly likely to be responsible for the satellite signal prior to onset. This in turn has major implications for weather and climate modeling. There are few, if any, other easily detectable signals of vegetation-climate interactions with such broad implications. With rare exceptions, ground phenological records are of limited duration or geographical extent.