Can age be predicted from diameter for the obligate seeder Allocasuarina littoralis (Casuarinaceae) by using dendrochronological techniques?

Abstract

In fire-prone regions, assessing stand age of obligate-seeding species provides an estimate of time since last fire. If a relationship exists between tree age and diameter, measuring the stem diameter of trees is a simple field method for determining age-class distribution within a stand. In this study, we examined whether age of the obligate seeder Allocasuarina littoralis could be estimated from diameter by using dendrochronological applications. Analysis of radial samples established that A. littoralis puts down annual growth rings. The relationship between the number of growth rings and stem diameter was tested for both male and female stems by using regression analysis. For female plants, this relationship varied significantly between sites. In contrast, male stems provided a strong relationship between age (as a function of the number of growth rings) and diameter, regardless of site. A regression model estimating age from stem diameter, based on male trees only, was subsequently developed and tested with data collected from trees of known age. Predicted estimates from stem diameter were within 3.76 years of the true age. Field measures of stem diameters can therefore provide a tool for estimating the fire history, especially time since last fire, in areas where stands of this species occur.