Summer-season Differences in NDVI and iTVDI among Vegetation Cover Types in Lake Mashu, Hokkaido, Japan Using Landsat TM Data

The improved Temperature Vegetation Dryness Index (iTVDI) can be used as an indicator of transpiration rates in mountainous areas. We investigated the influence of vegetation cover types on differences observed in iTVDI, together with NDVI in vegetation covers around Lake Mashu in a summer day. Based on the results of comparing NDVI and iTVDI values among 14 vegetation cover types, it was shown that the vegetation cover type differences could cause significant differences in iTVDI values. Shrub and grassland categories showed lower NDVI but higher iTVDI values, whereas tall trees except Erman's birch showed relatively higher NDVI but lower iTVDI values. The Erman's birch iTVDI values were higher than the other tall trees. These results suggest that the difference of vegetation cover types could be one of the factors that influence iTVDI values.