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A study of riverine plant communities in Tasmania, with especial reference to central east coast rivers

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Hughes, Jocelyne M R(Jocelyne Marie Ragody) (1987) A study of riverine plant communities in Tasmania, with especial reference to central east coast rivers. PhD thesis, University of Tasmania.

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Abstract

A study of riverine plant communities in Tasmania,
with especial reference to central east coast rivers
Plants growing in and along rivers have received little
ecological and conceptual attention. Current deterministic
and stochastic lotic community concepts are examined, along
with concepts in plant ecology (individualistic and
organismic concepts, plant succession, disturbance,
physiographic plant geography) and their application to
lotic plant communities. This theoretical framework is used
to investigate the spatial and temporal variability of
riverine plant communities in the island state of Tasmania
and to establish relationships between this variation and
major environmental factors. In order to establish a suitable strategy with which to
sample lotic plant communities, levels of hydrological and
chemical disturbance were investigated along Tasmanian
rivers. Annual flow records, monthly flow records, peak and
low flow records were used to derive an objective
hydrological regionalization for 77 rivers. Four contiguous
groups were determined with the south east region of the
island exhibiting hydrological regimes similar to those of
the drier areas of mainland Australia. The wettest areas, in
the south and west, have regimes with no analogue elsewhere
within mainland Australia. The water chemistry of Tasmanian
rivers displays similar contrasts, though variability tends
to be greater temporally than spatially.
To provide data on aquatic vegetation dynamics following
disturbance, 14 permanent plots were set up along the Swan
and Apsley Rivers, eastern Tasmania, and monitored over a 28
month period. Records were made of plant species composition
and cover, as well as measurements of water chemistry and
hydrology. Between-site (spatial) as well as within-site (temporal)
variability of aquatic plant communities along the study
rivers is pronounced. Species cover, diversity, richness and
turnover show significant changes after high and low
hydrological events, but less so between seasons. Spatial
variability is highly influenced by the water chemistry, and
within the brackish and freshwater components of the rivers,
hydrological variables are the major influence. This
evidence on site-specific succession does not support an
organismic interpretation, and lotic aquatic plant
communities appear to have a low resistance to disturbance
and low resilience after disturbance. Disturbance tends to
favour opportunistic species which recover rapidly
vegetatively, and tends to allow the coexistence of a
relatively high number of species which display
polydominance.
To provide data on the spatial distributions of riverine
communities, riparian and aquatic plants were intensively
sampled along the length and breadth of the Swan and Apsley
Rivers. Riparian plant communities vary longitudinally along
the river in response to geology and gradient index (which
combines altitude and distance from the drainage divide).
Lateral variations away from the river are a response to a
flooding gradient and substratum stability. Dense overhanging
riparian vegetation excludes growth of aquatic species,
though this situation is nullified where the canopy has been
cleared for agriculture or for roads. A geographical survey of aquatic plants along rivers in
Tasmania indicates that the plant communities are
predominantly influenced by filterable residue and colour
and to a lesser extent by substratum and hydrology.

Item Type: Thesis (PhD)
Keywords: Stream plants, Riparian flora, Plant communities, Hydrology, Water chemistry
Copyright Holders: The Author
Copyright Information:

Copyright 1987 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, 1988. Bibliography: leaves 249-275

Date Deposited: 19 Dec 2014 02:31
Last Modified: 11 Mar 2016 05:55
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