Vegetation Monitoring Study Using Leaf Water Content Index (lwci) and Ndvi

Leaf Water Content Index (LWCI) was proposed by Hunt, E. R. Jr., and et al (1987). At the beginning we tried and succeeded to develop this index for the practical application to the satellite remote sensing data such as Landsat TM. Next we performed vegetation monitoring using LWCI by SPOT Vegetation and we got same results. LWCI is not susceptible to influences from the atmospheric noise such as the haze and smoke, which are caused very often by fires or climatic conditions in the tropics, because it utilizes longer wavelength bands, SWIR (1.58-1.75μm) and NIR (0.79-0.89μm) than NDVI. This time we applied LWCI to the one-year time series of SPOT Vegetation 10 days composite data that were processed in advance to exclude the influences of clouds (Sawada, 2001). We tried to compare the seasonal change profiles of LWCI between the tropical agricultural lands (Thailand) and the temperate agricultural lands (Japan) in addition to the forest zone. The seasonal change profile of NDVI was created simultaneously and was compared, too. As a result, although it must be consider the influence of the snow in the case of Japanese winter season, both tropical and temperate evergreen forests in non-winter season showed the relatively same trend. As for the temperate deciduous forest, such evident time lag that is seen in the tropical deciduous forest was not observed. It was found for the first time that the seasonal change of LWCI could be observed even in the agricultural areas (paddy fields, upland farming fields, grassland), however, in both tropical and temperate zones the time lag between LWCI and NDVI profile was hardly observed. This fact seems to indicate that in the plant phenology of the temperate zone like Japan the moisture condition does not play more important role than that of the tropical zone, rather the cumulative temperature or photoperiod effect the plant phenology.