VEGETATION RECOVERY PROCESS ON LANDSLIDE STEEP SLOPE AFTER Alnus sieboldiana AND Miscanthus condensatus PLANTING WITH SIMPLE TERRACING WORK IN MIKURA-JIMA ISLAND, JAPAN

Abstract

Typhoon 9512 hit the island of Mikura-jima in 1995, causing many landslides and destruction of
forest vegetation. For long-term observation of vegetation change, a research plot was established on a landslide
slope in 2003. A simple terrace was built on this slope, which was planted with native species (Alnus sieboldiana
and Miscanthus condensatus) in 2000 to accelerate vegetation recovery. From 2003 to 2012, a vegetation survey
of the plot was conducted to elucidate the vegetation recovery process at an early stage. A. sieboldiana grew
steadily and its density of individuals decreased. The number of species gradually increased due to invasion of
new seedlings from adjacent forests, i.e. Castanopsis cuspidata, Persea thunbergii. We found some differences in
vegetation recovery from another research site, which is a landslide slope seeded with exotic pasture grasses by
helicopter in 2002. Seeding of exotic pasture gasses prevented the establishment of trees and reduces successional
velocity.