Recent Signal of Vegetation Change in Siberia Using Satellite Data

Global vegetation index data based on the observation of the satellite NOAA from 1980's enabled us to analyze the vegetation change over continental-scale regions for 20 years and more. An increasing trend of vegetation in boreal forests has been reported by some previous studies. Since the signal of such trend in the vegetation is probably apparent in the ecotone, detailed investigation should be required in the region of ecotone. This study targeted the ecotone from the boreal forest to the tundra in eastern Siberia, and examined the 19-year (1982 to 2000) trend of the satellite-derived vegetation index by using two kinds of parameters, i.e., the annual accumulative NDVI (ΣNDVI) and the annual maximum NDVI (MaxNDVI). As a result, we confirmed that ΣNDVI showed an increasing trend in the boreal forest as previous studies pointed out. By contrast, an increasing trend of MaxNDVI was found over the region to the north of the boreal forest (transitional zone between the boreal forest and the tundra). This suggests that signals due to the biomass increase or the vegetation change occurred in the region are detected.