RADIATION USE EFFICIENCY AND ABOVE-GROUND BIOMASS PRODUCTION OF SELECTED FOREST TREE SPECIES

Abstract

Radiation use efficiency (RUE). defined as biomass produced per unit ofradiation intercepted. is considered a genotype-specific constant. Ifthe amountof radiation intercepted is known. RUE can be used to predict the potentialbiomass production o]'a given tree species. A comparative growth analysis wasdone on some selected species, with the objective of determining their lightinterception characteristics, biomass production, and RUE. Similar-agedseedlings of six forest tree species: Acacia mangium, Eucalyptus grandis,Leucaena leucoccphala, Swietenia macrophylla, Azadirachta indica, andTectono grandis, were planted at the university farm, Peradeniya, from July1995 to June 1996. Regular sampling was done to determine above-groundbiomass and leal area. Canopy radiation interception was estimated fromsimultaneous measurements of incident and transmitted radiation. by tubesolarimeters. In a/I six species, above-ground biomass production was found tvbe linearly related to cumulative intercepted radiation. The slopes of therelationships, which indicate R liE. showed significant inter-species variation.The greatest RUE was observed in E. gram/is (3.05 gA1fI) and the least inAzadarachta indica (0.296 gUfI). The differences in RUE were primarilyresponsible for the differences between species in above-ground biomassproduction. Radiation interception by the canopies ofthe different species wascharacterized by the light extinction coefficient, which showed significant interspeciesvariation. These parameters offer a promising approach Jill' modellingand prediction ofbiomass production by forest tree species.