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Understorey dynamics following partial logging in Eucalyptus delegatensis forests on the Central Plateau, Tasmania


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Gibbons, Andrew K.(Andrew Kevin) 2003 , 'Understorey dynamics following partial logging in Eucalyptus delegatensis forests on the Central Plateau, Tasmania', PhD thesis, University of Tasmania.

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Partial logging in high-altitude E. delegatensis forests involves the retention of
approximately 50 % of original forest basal area, and was implemented to overcome the
problem of "growth check" in regenerating eucalypts following clearfelling. It is
increasingly being carried out in these forests in an effort to provide income to
landowners while still allowing regeneration of the overstorey eucalypts.
This thesis looks at the effects of partial logging on understorey floristics and structure
in both, the short (-2 years), and the long (15-20 years) term. Analysis of a floristic,
structural and environmental dataset using multivariate and ANOVA techniques found
that two understorey types, grassy and shrubby, were present, and that short term trends
included reduced cover of all lifeform groups, reduced understorey height, species
richness and structural complexity, and increased bare ground cover and soil
disturbance. Four of these trends, increased grass and forb cover, decreased shrub cover
and structural complexity, were still apparent 5-8 years after logging, and two, reduced
shrub cover and habitat complexity, 16-21 years after logging, particularly in shrubby
forest. These changes were attributed to the reduced cover of the overstorey and
subsequent changes in the light/temperature/moisture regimes of the forest floor
Effects of plantation establishment in wetter areas of this forest type were similar to
those of partial logging, but of a greater magnitude and duration.
Ecological processes structuring the understorey were examined by, first, looking at
changes in species cover/abundance under individual overstorey eucalypts and in forest
gaps in unlogged forest, and, second, with a laboratory shading/disturbance experiment.
It was found that canopies of overstorey eucalypts were causing distinct patterns in
understorey distribution. Species richness and cover increased moving from trunk to
canopy edge to forest gap and from unshaded to shaded sector of forest gaps primarily
due to the inhibitory effects of high litter and shade under trees, and cold induced
photoinhibition in high light areas of gaps. Chlorophyll fluorescence measurements
confirmed the requirement of shade for, the shrub Lomatia tinctoria, and the sedge
Lomandra longifolia, and the ability of grasses to out compete these species in full sun,
mimicking the patterns observed logged forest.
Results are discussed in relation to the theory of ecological resilience and it is suggested
that increasing divergence of understorey will occur with each logging and/or plantation
rotation and may lead to shifts in forest/grassland boundaries.

Item Type: Thesis - PhD
Authors/Creators:Gibbons, Andrew K.(Andrew Kevin)
Keywords: Understory plants, Forests and forestry
Copyright Holders: The Author
Copyright Information:

Copyright 2003 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 (Ph.D.)--University of Tasmania, 2003. Includes bibliographical references

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