Temporal stability of an NDVI-LAI relationship in a Napa Valley vineyard



    Corresponding author
    1. Earth Systems Science & Policy, California State University/Monterey Bay, Seaside, CA, 93955, USA
    2. Earth Science Division, NASA Ames Research Center, Moffett Field, CA, 94035, USA
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Mr Lee Johnson, facsimile + 1 650 6044680, email ljohnson@mail.arc.nasa.gov


Remotely sensed values for normalised difference vegetation index (NDVI) were derived periodically from high-resolution Ikonos satellite images during the 2001 growing season, and compared with ground measurements of vineyard leaf area index (LAI) during that same period. These two derived variables were strongly related in six vineyard blocks on each of four occasions (R2= 0.91 to 0.98). Linear regression equations relating these two derived variables did not differ significantly by time-step, and a single equation accounted for 92 per cent of the variance in the combined dataset. Such temporal stability in that relationship opens the possibility of transforming NDVI maps to LAI units, at least on a localised basis, and minimising (or even eliminating) subsequent ground calibration. This reduction in fieldwork would then decrease information cost for viticulturists who wish to monitor LAI sequentially within season, or who wish to track year-to-year changes in climax LAI with a single image collected annually. To take advantage of this cost reduction, temporal consistency in spectral data values comprising NDVI must be assured. This present paper addresses that issue.