Crown Assessments Improve Regression Estimates of Leaf Area in Jarrah Trees (Eucalyptus marginata)

Abstract

Regression equations for estimating the single-sided leaf area of individual jarrah trees (Eucalyptus marginata Donn ex Smith) are presented. The destructive measurement of 96 trees on five sites and over three seasons provided the data that were used to relate leaf areas to crown dimensions and assessments. Substantial variation in jarrah leaf area across sites and between seasons weakens normal allometric relationships. Combining crown dimensions with assessments of the foliage density and crown size produced substantial improvements in the estimate of leaf area, raising the r² from 0.48 for a model based on crown depth to 0.92 for a model that included assessments of crown development and foliage density. Because the expanded equations consider the foliage density, they avoid the site and seasonal dependence found in simple allometric relationships based only on stem diameter, sapwood area or crown dimensions.