GROWTH-RATE AND BASAL AREA RESPONSE CURVES OF 4 EUCALYPTUS SPECIES ON MT WELLINGTON, TASMANIA

The heights, diameters and regrowth basal areas of 22-yr old fire-initiated regeneration of Eucalyptus delegatensis ssp. tasmaniensis, E. urnigera, E. coccifera and E. johnstonii were measured over altitudinal, solar radiation and drainage gradients on Mt. Wellington, Tasmania. The growth rate responses to the altitude gradient-complex vary from linear to curved depending on the performance measure, the species and the gradient. Much of the variation in growth rate appears to be a direct response to the physical environment. However, disparities between trends in growth rate and trends in regrowth basal area are consistent with the hypothesis that competition (sensu Grime 1979) is more important in productive environments and less important in stressful environments. A glasshouse trial with Eucalyptus seedlings indicated that potential growth rates decline with increasing altitude of seed source.