Measurement and prediction of biomass and carbon content of Pinus pinaster trees in farm forestry plantations, south-western Australia

A total of 148 Pinus pinaster trees from 18 farm plantations in south-western Australia were destructively sampled to develop biomass and carbon mass prediction equations for inventory application. Sampling covered a range of ages (1-47-year-old), sizes (e.g. DBH 0-47 cm) and spacings (close- and open-spaced arrangements). Equations were developed to predict biomass and carbon mass of whole-trees and tree components (stems, crowns, tops and roots) as functions of stem diameter (DBH), tree height (h) and height to crown base (h(c)) or basal stem diameter (d(10)) of small trees. One equation was sufficient to predict biomass (or carbon mass) of both close- and open-spaced trees as a function of DBH and h(c). For developing prediction equations a weighted non-linear (WNL) model was always best if DBH was included in the predictor variables. Either a log-transformed allometric (LTA) model or the WNL model were best for predictions as a function of d(10), but a weighted combined variable (WCV) model was never best. Root:shoot (R:S) ratio decreased with increasing tree size in both close- and open-spaced trees but was higher in open-spaced trees than close-spaced trees of the same size. From literature review, we conclude that increased partitioning of biomass to roots in open-spaced stands may be due to increased light availability or, more likely, more pronounced root thickening on open-spaced trees in response to greater mechanical stress from wind sway. (C) 2002 P. Ritson. Published by Elsevier Science B.V. All rights reserved.