Many slope surface failures occurred on weathering granite in Suzuka range.
These slope surface failures are characterized as follows. Thickness of slope failures is very thin such as less 1m and the sliding mass contains many roots of plants. However, weathering granite as underlying basement rocks does not contain roots of plants caused by no existence of crack in itself.
These slope failure has been named slope failure along roots of plants by author. In the other hand, there is ancient forest around Tagami peak in Tanagami mountains near Suzuka range. Slope surface failures are not located in this area due to vegetate many big trees having strongly their roots into underground. This paper describes features of slope failure along roots of plants and reinforcing effects of roots of plants in soil against slope failure based on comparison of the both cases.