TWO METHODS FOR TREE VOLUME ESTIMATION OF Acacia melanoxylon IN PORTUGAL

Abstract

Two models were developed to evaluate total volume under and over-bark of Blackwood (Acacia melanoxylon R. Br.) stand trees. By variance analysis regarding volume with and without bark it was confirmed that trees age is responsible for 48 to 50% of its volumetric behaviour. Considered the averages of those variables and regarding the three homogeneous groups of the studied sites, a single model type was used (v=β₁d^β2h^β3) for estimating volumes. The critical errors are between 72 and 195 dm³ under-bark, and 82 and 212dm³ over-bark. The model that uses sites as dummy variables to the estimation of stand tree volumes is the same, and this method performs maximum expected errors with values of 155 dm³ (under-bark) and 169dm³ (over-bark), to mean maximum volumes of 1362 and 1459 dm³ respectively.The use of dummy variables is a more expedite and rapid modelling method, and its maximum expected errors perform lower values.