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Dynamics of vegetation after cable and ground-based logging

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Peacock, Ross J.(Ross Johnston) 2003 , 'Dynamics of vegetation after cable and ground-based logging', PhD thesis, University of Tasmania.

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Abstract

The relationship between forest resource management and the conservation of
biological diversity. is a controversial one, with the steep country logging of oldgrowth
forests in Tasmania being the source. of much of this attention, due to the
perceived greater impacts of logging on steep slopes and the greater damage caused
by the large modern cable systems.
Retrospective (chronosequence) and permanent plot studies of cable and groundbased
logging in forests aged 0-54 years on steep slopes in southern Tasmania and
comparable unlogged sites indicated that following both logging treatments, there
was a gradual recovery in floristic composition towards mature forest. Vascular
plant species richness recovered more rapidly in the ground-based logging
treatment than the cable logged treatment. Differences between treatments were
confined to the initial recovery stages where treatment effects were evident in the
extent of soil, woody debris and micro-habitat disturbance. Following canopy
closure and self-thinning (i.e. after 20-30 years) sites logged by the two techniques
resemble each other in vascular species composition and that of mature unlogged
forest. However, differences still existed in forest structure and in the composition
of the obligate epiphytic fern flora (particularly that present on Dicksonia caudexes).
Generally cable logging did less physical damage to vegetation than ground-based
logging. Ground-based logging led to a greater degree of floristic change than cable
logging. The pattern of vegetation change was related to the degree and nature of
soil and habitat disturbance.
Conventional ground-based thinning of 30 year old regrowth forest led to a greater
change in the composition of the ground stratum (an increase in the cover of weed
and other herbaceous species) than cable thinning. Cable thinning caused little soil
disturbance and ground fern species rapidly regenerated rhizomatously.
Herbaceous and weed species were infrequent after cable thinning.
Cable logging practices adjacent to or through retained stands of streamside
vegetation can result in significant changes to the vegetation. This can occur during
all phases of tree falling, establishment and movement of cable settings, yarding,
fire break construction and the regeneration burn. Many of the detrimental effects
of cable logging adjacent to retained stands of streamside vegetation are indirect,
resulting from actions such as windthrow, tree health decline and crown scorch
from regeneration burning. While there has been an improvement in forest
practices since the 1980's when the attempted full suspension logging over
streamsides was ended, the on-going health and viability of retained streamside
vegetation is still in doubt.
Ground-based logging inflicted greater levels of mortality than cable logging on
populations of the tree fern .Dicksonia antarctica, a functionally important
understorey species in· wet forests. Approximately 80% of the D. antarctica
resprouted following cable logging prior to burning. Only 40% survived the
regeneration burn. This was reduced to 27% after 10 years. While ground-based
logging resulted in greater mortality, it led to a greater degree of new sporophytic
recruitment to the D. antarctica population. The significant reduction in the
abundance of this slow growing species following logging has implications for the
conservation of obligate vascular epiphytes that use it's caudex as a substrate.
The vascular epiphytic flora, the primary late successional specialist group, was
almost completely lost following cable logging. Epiphytes were slow to recolonise
following either cable or ground-based logging, although their recovery was more
rapid following ground-based logging. While most of the vascular epiphytic species
recovered 30-50 years following either logging method, their abundance was
reduced and the diversity of substrates available for colonisation was limited.
The response of vegetation to logging treatment was studied at the three levels; the
community, the functional group and the species. No general statement can be
made about the logging treatments across these levels as the treatment response
was not uniform. However, the individual species level of response provided most of
the understanqing of processes operating following either logging method in terms
of how these treatments differ in their spa~ial variability, the biological legacies they
create and t;heir intensity. The use of permanent plot monitoring associated with
the chronosequence studies effectively validated the generalised chronosequence
trends, at least for the short term predictions, and also questioned many of the
trends described elsewhere in the literature from chronosequence studies which
lack the rigour of an individual species level of experimental treatment and
monitoring.
The examination of cable and ground-based logging in a controlled manner has
provided a depth of understanding to previous logging studies that was generally
not available. It has added additional emphasis to the role of logging as both a
process of vegetation disturbance and one of establishing biological legacies which
mediate the regenerative response. It also questions much of the literature which
describes vegetation responses in terms of generalised hypotheses, eg the
intermediate disturbance hypothesis, as vegetation responses are not uniform
across differing levels of examination.

Item Type: Thesis - PhD
Authors/Creators:Peacock, Ross J.(Ross Johnston)
Keywords: Forests and forestry, Logging
Copyright Holders: The Author
Copyright Information:

Copyright 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 copyright owner(s).

Additional Information:

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

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