An integrated analysis of 33 Eucalyptus trials linking the onset of competition-induced tree growth suppression with management, physiographic and climatic factors

One of the greatest difficulties associated with controlling competitive vegetation during the establishment of eucalypts relates to the timing and planning of 'weeding' operations. This may be due to site related variability in vegetation species distribution and abundance, climatic conditions and methods of site preparation. Using data from 33 eucalypt vegetation management trials, multivariate statistical techniques were used to determine whether any climatic, physiographic or management related variables could be related to the time taken for competition-induced tree growth suppression to occur. Altitude, the method of site preparation (burning versus not burning) and the interaction between these two factors were significantly related to the timing of tree growth suppression. Regardless of the method of site preparation, the onset of competition-induced tree growth suppression occurred earlier at lower altitudes, where the vegetation was more diverse and vigorous. At higher altitudes, burning appears to stimulate the earlier growth of vegetation, reducing the time for competition-induced tree growth suppression to occur.