Abstract
NDVI from satellite data offers various kinds of physical values related with plants. Landsat TM has high resolution and gives the seasonal change of NDVI for each land cover. Then, we proposed seasonal change models for NDVI using a logistic curve. NDVI for each land cover except water surface fitted very well with logistic curves for less than 300 Julian day. We modified the logistic curve adding a negative-slope line. This modified logistic curve expresses periodic change and gave good fit with NDVI. On the other hand, leaf area, leaf length, dry weight, and spectrum reflectance were measured for paddy pots in greenhouse cultivation. These results led to a series of relationship among these parameters. Finally, the relationship between NDVI and leaf area index was obtained. Using these regression curves for NDVI, the temporal and spatial distributions of LAI of paddy fields in the watershed could be estimated.
