ABOVEGROUND BIOMASS PRODUCTION AND NUTRIENT ACCUMULATION OF A <em>GMELINA</em> <em>ARBOREA</em> PLANTATION IN SARAWAK, MALAYSIA

Abstract

A biomass and nutrient content study was carried out on 6-y-old Gmelina arborea, established on abandoned shifting cultivation sites for the purpose of site rehabilitation. The aboveground biomass of small-litter standing crop, undergrowth and overstorey was determined by destructive sampling of two 10 X 20 m plots. Total mean aboveground biomass was 92.1 t ha^-1 Biomass comprised 92.3% overstorey, 3.5% undergrowth and 4.2% litter. Aboveground tree biomass was composed of 68.5% stem wood, 8.8% stem bark, 12.3% branches, 5.1% dead branches, 3.0% foliage and 2.3% twigs. The overstorey biomass contained 394 kg ha^-1 K, 236 kg ha^-1 N, 214 kg ha^-1 Ca, 70 kg ha^-1 Mg and 17 kg ha^-1 P. A large proportion of these nutrients (55.1 to 71.7%) was immobilized in the stem wood and bark. Remaining nutrients were immobilized in twigs and branches (14.4 to 25.8%), foliage (8.6 to 20.5%) and dead branches (1.7 to 4.0%). Biomass and nutrient accumulation is compared to those of other Gmelina plantations and fallow forests in the tropics.