Abstract
We investigated the current vegetation conditions on Shirasu steep slopes susceptible to shallow landslides, and particularly the role of root networks and topsoil in preventing shallow landslides, in abandoned forests 4 years after plantation clear-cutting. The study area was located near Kagoshima Airport, Kagoshima Prefecture. To conduct vegetation surveys and take topsoil thickness measurements, we established quadrats on seven slopes: five with steep slopes (>40°) and two with relatively gentle slopes (30°). Vegetation on the steep slopes prone to shallow landslides was less abundant than that on the relatively gentle slopes. If there is no reforestation after clear cutting on steep slopes, vegetation recovery is substantially delayed in comparison with that on reforested slopes, and recovery of the role of forest root networks to prevent shallow landslides is substantially delayed. Moreover, the average value of topsoil thickness on the steep slopes was approximately 40 cm. Based on the relationship between shallow landslide occurrence and topsoil development, this value of approximately 40 cm indicated that shallow landslides could be expected to occur.
https://ror.org/03ss88z23 
