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Abstract

This thesis examines the effects of agricultural and conservation management practices
on grassy communities in the sub-humid, low altitude Midlands of Tasmania.
The results of an extensive survey were examined to assess the effects of grazing by
sheep and cattle, fertilisation and the introduction of exotic pasture species on the grassy
communities.
Sites were classified according to the degree of pasture conversion and the level of the
main limiting nutrient phosphorus, by annual rainfall and by geological substrate.
Exotic species replaced native species with increasing degrees of pasture conversion and
levels of phosphorus. Effects of management varied rainfall and different geological
substrates. Raunkiaer life-form groups were a useful aid in the identification of patterns
of species' responses.
Exotic therophytes and flat/versatile rosette hemicryptophytes were the most invasive
exotic life-forms in native communities. The native species in the flat/versatile rosette
and caespitose hemicryptophyte life-form groups were the most tolerant of disturbance.
The effects of fertilisation alone on native communities were increased agricultural
productivity but a reduction in the diversity of native species and the conservation
values of the communities.
At the Township Lagoon Nature Reserve, three levels of grazing pressure, light in the
reserve and moderate and higher levels in adjacent paddocks, were compared. The
moderate level of grazing altered species composition but native species diversity
declined only under the high grazing regime.
A replicated experiment, with a gas flame used to provide heat energy, compared the
responses of vegetation to burning. Treatments were single bums at four different times
of the year, bums at those times in two consecutive years and a no burning treatment.
Phenology varied considerably between species. Burning promoted most species when
it occurred a short time before main growing season of that species. In addition, most
species were suppressed by burning which occurred during their main growing season or before seed dispersal. Burning in two consecutive years tended to increase the seasonal
effects.
The effects of weeding techniques on species and life-forms in grassland dominated by
exotic species were examined over a 10 month period from spring 1991. The weeding
techniques were removal of topsoil, herbiciding and burning. The effects varied
between species, and depended on the protection of buds from disturbance, the presence
of seed for recruitment and the conditions for growth of the species.
The levels of dissimilarity between the responses of all pairs of species to disturbance in
this study were calculated using the Gower metric index of dissimilarity. The degree of
dissimilarity within the life-form groups was less than that between the life-form groups
for only a small proportion of comparisons.
Species were classified using TWINSPAN into response or functional groups based on
their responses to disturbance. Groups were classified mainly by responses to
agricultural management, and the responses to grazing level, burning and weed-control
techniques were highly variable. The response groups were not associated with the
Raunkiaer life-form group to which the species belonged.
The responses of species classified into Raunkiaer life-form groups were highly
variable. The life-form group was an aid to describing overall responses of species, but
would be a poor predictor of the likely response of any one species to management.
Active management of grasslands could be used to manipulate their species composition
as many species are highly sensitive to the types and levels of disturbance.
Conservation management of native grassy communities must be based on the site-specific
responses of individual species to disturbance.

Item Type:	Thesis - PhD
Authors/Creators:	Zacharek, A
Copyright Holders:	The Author
Copyright Information:	Copyright 1997 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:	Examines the effect of agricultural and conservation management practices on grassy communities in the sub-humid, low altitude Midlands of Tasmania. Examines the effects of grazing by sheep and cattle, fertilisation, the introduction of exotic pasture species, and the responses of vegetation to burning. Thesis (Ph.D.)--University of Tasmania, 1997. Includes bibliographical references. Examines the effect of agricultural and conservation management practices on grassy communities in the sub-humid, low altitude Midlands of Tasmania. Examines the effects of grazing by sheep and cattle, fertilisation, the introduction of exotic pasture species, and the responses of vegetation to burning
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