Global warming's influence over the last 30 years, along with soil dehydration in the Taisetsu mountains has resulted in shrubbery such as Dwarf bamboo (Dwarf bamboo kurilensis), a species of dwarf bamboo, and Japanese Stone pine (Pinus pumila) (an indicator of soil dehydration), increase in area of distribution while many herbaceous species of alpine plants have reduced in distribution area to the extent where some extinction has occurred. This study, using multipolarization of ALOS satellite PALSAR L-band microwave (HH/HV) data, has developed a model to estimate soil moisture in densely vegetated areas to clarify factors in the seasonal variation of soil moisture in an area with fluctuating vegetation and so clarify factors in the casual relationship between soil dehydration and vegetation fluctuation in a wide area. Moreover, conducting this research will enable identification of potential areas where Dwarf bamboo may easily invade, and thus contribute to environmental measures.