Secondary vegetation and succession of abandoned grazed grasslands in upland Southwest Honshu, Japan

Abstract

Six stands of secondary vegetation at different ages from abandonment, an in-using grassland and a climax forest in upland Southwest Honshu, Japan, were surveyed in summer 1998. The grasslands of 0-2 years old from abandonment had the least species composition and one layer. Shrublands (with age of 32 yr.) had two layers in structure and were dominated by Ilex crenata and Miscanthus sinensis or Arundinaria variegata, with tree saplings colonizing among the shrub layer. The young Pinus densiflora forests (with age of 20-30 yr.) formed 3-4 layers, co-dominated with Clethra barbinervis. Mature secondary forest (with age of 33 yr.) was constructed of four layers, dominated by Quercus serrata and Castanea crenata. Fagus crenata climax forest had four layers in structure. As the age increased, height of the vegetation (as 25 m in maximum) increased, together with its complexity (four layers in its vertical structure). Both dominance degree (DD) and basal area (BA) increased till the climax (as 7438 for DD and 6109cm2 100m^<-2> for BA), while coverage of herb layer decreased to 18.3%, thought total coverage kept constant from the very beginning. Peaks of species number per plot (as 40 species 100 m^<-2> in a 32-yr-old stand), trunk density (as 115±52 100 m^<-2> in the 30-yr-old stand) and mortality (as 11.8% for trunk density, or 6.5% for BA in a 33-yr-old stand) appeared at intermediate age of the secondary succession.