The ecology and silviculture of Eucalyptus delegatensis : R.T. Baker on dolerite in Tasmania

Eucalyptus delegatensis is a widespread dominant of montane forests in southeastern Australia, where is occupies sites of widely varying moisture status and understorey type. The age and size class distributions of E. delegatensis on 23 sites of varying precipitation over its range on dolerite in Tasmania are strongly related to the floristic composition of the understorey vegetation and to moisture availability. No stands are even-aged, but all stands exhibit evidence of periodic rather than continuous recruitment; the periodicity of past recruitment events increasing with more mesic conditions. There is evidence for a change towards less frequent recruitment events in the higher rainfall stands since white settlement. An explanation for the variations in regeneration patterns is sought in the complex interactions between climate, fire frequency, fire intensity and understorey vegetation type. The trees in multi-aged forests at the dry end of the environmental range of E, delegatensis are extremely fire resistant while the survival of the even-aged saplings is dependent upon their height and bark thickness. Regeneration typically follows forest fire but experimental studies showed that germinates readily establish on cultivated seedbeds. Marked intraspecific competition occurs between the regeneration and the overwood trees. Experiments with germinates, seedlings, and advance growth indicate that soil drought prohibits rapid growth of regeneration beneath overwood while the higher levels of moisture available in forest gaps supports a dense stocking of vigorously growing saplings, Total removal of canopy cover results in a microclimate with greater maximum and lower minimum ground surface temperatures than in an environmentally similar unlogged stand. The poor health of regeneration on some high-altitude clear-felled forest sites is explained by the interactions of canopy cover, frost damage and topography. The various types of eucalypt silvicultural practices are subjectively classified as intensive, partial and selective systems. It is suggested that dry E. delegatensis forests are well suited to selective logging.