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Abstract

Studies on vegetation and insect predation were conducted during
the period 1982-84 at the Ridgeway Park Reserve, Tasmania. The vegetation
of the area is eucalypt forest and woodland which varies in
composition, dominance and structure. Soil type, topography, the level
of grazing and incidence of fire also vary within the study area.
The influence of soil type on moisture availability was investigated
by comparing the vegetation on sites receiving the same incident solar
radiation. The majority of species experience a shift in distribution
over the three soil types such that with increasing radiation the species
reach their peak frequency first on the brown earth, then on the podzolic
soil and finally on the podsol. This pattern conformed to a model of
moisture availability devised for the three soils. Species that did not
conform to the model were either particularly vulnerable to the effects
of grazing or fire, opportunists or restricted to one or other of the
three soil types and hence a particular set of soil nutrient conditions.
The effects of insect grazing on sapling eucalypts on north and
south-facing slopes, which differed in geology, were assessed by monthly
monitoring of insect damage and by deterring insects from grazing certain
trees through the use of insecticide. On every tree percentage damage,
and the amount of different types of damage, leaf loss, mean shoot length,
the number of leaves per shoot and the percentage of damaged leaves,
were measured on the current season's shoots. A limited sample of the
same data was collected on leaves approximately one year old.
Overall, there were few significant differences in the level of
these variables between the different species and sites. Percentage
damage figures were comparatively low (7-12%) and there was no significant
difference between the species. However, damage was significantly higher
in the most mesic, least fertile site. Percentage damage, and leaf and
shoot loss were combined to derive a figure for the total damage to each
species (29-41%). This was significantly higher in E. obliqua compared with the other species.
The patterns of insect defoliation may have been considerably
altered as a result of a drought experienced during the course of the
study. Insect activities may effect forest community composition, but
only as part of a web of inter-relationships whose effects vary, between
the species, in space and time.

Item Type:	Thesis - Research Master
Authors/Creators:	Marks, F
Keywords:	Eucalyptus
Copyright Holders:	The Author
Copyright Information:	Copyright 1985 the author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).
Additional Information:	Thesis (M.Sc.)--University of Tasmania, 1986
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