EFFECT OF GAP LIBERATION ON THE PERFORMANCE AND GROWTH OF DIPTEROCARPTREES IN A LOGGED-OVER RAIN-FOREST

Large parts of southeast Asian dipterocarp rainforests have been overl ogged by applying different systems of selective cutting. Logged-over forests are expected to re-establish the original dipterocarp stock th rough natural regeneration. Post-logging silvicultural operations, not ably crown liberation and enrichment planting, are conducted to ensure sustained yield. These techniques have largely failed to achieve the desired goal. We tested the effect of gap liberation on the performanc e and growth of dipterocarp trees in an overlogged concession area in south Kalimantan, Indonesia. Twelve gaps, 500-1600 m(2) in size, were sampled based on the occurrence of ephemeral dipterocarp seedling stoc k (notably Shorea spp.) under the canopy. Six gaps were opened up 6 ye ars after the logging and inventoried, together with the untreated gap s, 12 years after the logging. In liberated gaps, dipterocarps account ed for 77% of the total basal area, compared with 20% in the untreated area. Survival of dipterocarps was 33% higher and diameter twice as h igh in liberated gaps as in the untreated plots. In height, no signifi cant difference was detected. Liberation also improved the quality of dipterocarp trees in terms of stem and crown form. The volume of red m eranti (Shorea spp.) in liberated gaps was 90 m(3) compared with 36 m( 3) in the untreated area. Gap liberation was proved as a silvicultural ly and economically feasible management alternative of overlogged dipt erocarp rainforests.