ALLOMETRY OF WOODY BIOMASS AND LEAF AREA IN FIVE TROPICAL MULTIPURPOSE TREES

Abstract

To derive allometric equations for leaf area and woody biomass, and to test for differences due to tree age and planting density and geometry, two field experiments were conducted on the island of Maui using Acacia auriculiformis, Acacia mangium, Eucalyptus camaldulensis, Gliricidia septum and Leucaena diversifolia. In the first experiment, harvest at 6, 12, 18 and 24 months of a 2 x 1 m spacing showed that woody biomass allometrics did not differ for any of the species over time. Leaf area equations differed among harvests for G. sepium due to seasonal leaf shedding, and for L. diversifolia, due to episodic psyllid attack, but did not differ for the other species. A second series of plots containing A. auriculiformis only were started six months later and harvested at 6, 12 and 18 months; there was no difference attributable to season as opposed to tree age. In the second experiment, A. auriculiformis and L. diversifolia were grown in four spacing treatments: 1x1, 2 x 1 , 2 x 2 , and 4 x 0.5 m. Harvest at 24 months showed no differences in leaf area or woody biomass allometric equations among spacings for either of these species. Combined across both experiments, the exponents of the leaf area allometric equations did not differ from 2.0,supporting the "pipe model"theory of physiological regulation of leaf area. The exponents of the biomass allometrics were significantly different from 2.0 (generally near 3.0), implying that sampling and mensuration methods based on diameter squared are biased.