Biomass and carbon accumulations of acacia trees planted on tropical peatlands

Abstract

Acacia (Acacia crassicarpa) is a fiber source for pulp industries, adaptive on tropical peatlands and has been planted intensively since the early seventies. Considering the fragility of peat and its low nutrient content along with the complication to manage water conducive environment to the tree growth, the sustainability of this plantation is under rudimentary inquiry. Peat loss may occur due to subsidence, emission, and surface runoff whilst biomass accumulation will result in carbon enhancement. This study aims 1) to evaluate growths of Acacia trees planted on tropical peatlands with different peat thicknesses; 2) to obtain allometric model to represent the growth of the tree parts; and 3) to estimate biomass and carbon accumulations and their rate in a few rotations. Destructive samples were taken from three different sites with different peat thicknesses and separated into the root, knud (buttress root), stem, branch, and leaf. An allometric model was introduced to represent each growth of the tree parts and to estimate the accumulation of biomass and carbon. The result shows Acacia grew better in thick peatlands, larger than 1 meter. The model can relate the tree parts specifically to estimate the tree biomass. In one hectare of one rotation within 5 years, total biomass ranges 36.3–443.7 tonnes, and total carbon absorbed ranges 17.4–213.0 tonnes. Thus, successive rotations would potentially result in additional thickness of organic matter at the rate of 0.07– 2.08 cm/y, and carbon enrichment at the rate of 1.74–19.98 tonnes/y. This biomass and carbon enrichments would lessen the losses and greenhouse gas emission from the peatlands.