TREE GROWTH IN PRIMARY LOWLAND AND HILL DIPTEROCARP FORESTS

Abstract

Information is analysed and summarised on tree growth over long term in 2-ha plots in primary lowland dipterocarp forests in Pasoh Forest Reserve (1971-84) and Sungei Menyala Forest Reserve (1947-85), and in primary hill dipterocarp forest in Bukit Lagong Forest Reserve (1949-85). About 64% of trees ≥ 10 cm DBH grew at slow rates around 1 mm y^-1 and species groups differed in their rates of growth in the following sequence: understorey < main canopy < emergent = pioneers. In the longer-term plots at Sungei Menyala and Bukit Lagong, canopy species (emergent and main canopy) formed 95% of the fastest growing individuals, and light hardwoods 80%. In the Pasoh plots, 77% of the fastest growing individuals were canopy species, and light hardwoods and medium hardwoods were
together 80%. In populations of understorey species and hardwoods, generally regarded as slow growers, there were individuals that grew at high rates comparable to that of fast-growing individuals of canopy species. Fast-growing trees of canopy species, especially dipterocarps, are estimated to be as young as 60 years at a size of 30cm DBH.