Abstract
Fossa Magna and the Median Tectonic Line are the largest tectonic lines in Japan. The north Alps, a mountain range upheaved by crustal movements, border the western verge of Fossa Magna, with the Norikura volucanic range. In these mountain ranges, grassy plains have formed on lava plateaus. Highlands near treelines have also formed in a similar condition. In the outer zone of the Median Tectonic Line, grassy plains have formed on Paleozoic Mikabu Green Tuff, which has good water permeability. This line extends to as far as the Shikoku and Kanto districts, and there are mamy grassy plains and golf courses along it. Thus, stable subclimax grasslands of Japan are mostly distributed in the area where the rain water permeability is high and the soil water availability is low because of geographical and geological features.
