SHORT-TERM POPULATION DYNAMICS OF DIPTEROCARP TREES IN A LOWLAND RAIN FOREST IN PENINSULAR MALAYSIA

Abstract

Based on an initial census in 1987 and a repeat census in 1990 of all trees <1 cm DBH in a 50-ha plot in Pasoh Forest Reserve,
the Dipterocarpaceae suffered a significantly higher mortality of 6.88% than the total flora which suffered a mortality of 3.81%. With about 80% of the total stems in the 1 to ≤ 5 COT DBH class for both the Dipterocarpaceae and the plot flora, mortality at this size class was significantly higher than in the ≥ 5 cm size class for both groups. Recruitment of 4.80% into the lowest size class for the Dipterocarpaceae was significantly higher than that at 1.55% for the plot flora. Resultant population change for both groups was similar, a reduction of 2.26% for the plot and 2.08% for the Dipterocarpaceae. At the species level, three categories of dynamic changes were recognised. The commonest light hardwood Shorea species, and one each of Hopea and Parashorea, suffered high mortality compensated by high recruitment. Shorea leprosula was the most dynamic species. In the medium hardwood species of Dipterocarpus, and the heavy hardwood species of Vatica and in Neobalanocarpus heimii, both mortality and recruitment were low. In the balau heavy hardwood group of Shorea species, mortality was low but recruitment was moderately higher.