Post-logging regeneration in a mature tropical rainforest stand, Gajabuih, Ulu Gadut, West Sumatra

Abstract

We examined regeneration processes within a permanent 0.9 ha tropical rainforest plot located in the West Sumatran Ulu Gadut region at about 630 m altitude. Our study site, the Gajabuih plot (GJB), was heavily logged in 1997. This induced conspicuous decreases in species number and diversity. Logging affected major climax species, few of which survived as standing trees. Species ordination analysis revealed a shift from a mature forest similar to that of a little-disturbed plot in the same region (PIN) to a young regenerating stand dominated by vigorous pioneer secondary forest species, such as Villebrunea rubescens (shade tolerant, random habitat preferences) and Mallotus paniculatus (widely dispersing species). Sprouter species made up 79% of calculated importance values in the regenerating stand. Single-stemmed trees (77% of total basal area) dominated the stand irrespective of species groups (survived or newcomer). Single-stemmed and multi-stemmed trees tended to be located on low slopes and ridge sites, respectively. The life strategy spectrum of the trees suggests that increases in the incidence of sprouting were promoted by heavy disturbance and variation in topographical structure. Sprouting abilities were negatively correlated with potential growth rates, as were shoot mortalities after storm damage. However, sprouting ability was positively correlated with the mechanical strength of trees (stem hardness). Using this information, we explored regeneration capacity by sprouting of tropical forests across environmental gradients of resources and disturbance.