Riparian woodland condition in relation to lippia (Phyla canescens (Kunth) Greene) and fire management, southern Queensland

Galea, Lucy M. E. (2014) Riparian woodland condition in relation to lippia (Phyla canescens (Kunth) Greene) and fire management, southern Queensland. Honours thesis, University of Southern Queensland. (Unpublished)

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Abstract

The implementation of inappropriate management regimes encourages alien species invasion into native ecosystems. Disturbances, such as fire, flooding and grazing, create a unique window of opportunity for invasive species to colonise areas not previously invaded. Fire regimes can be changed through the introduction of foreign species and may induce detrimental ecosystem effects including increased tree mortality, an increase in bare ground and further invasion by foreign species.

Phyla canescens (lippia) is an invasive introduced species covering over 5.3 million hectares of the Murray-Darling Basin. Many potential control methods have been attempted. However, the response of lippia to fire as a potential management tool has not previously been studied.

The general question of this research was: what is the effect of a prescribed fire on lippia, the vegetation structural components and the soil seed bank of a vegetation remnant in a highly modified agricultural landscape? This research examined the following specific hypotheses: that there is no difference in the abundance of lippia between burnt and unburnt treatments, six months after a prescribed burn; that there is no difference in the abundance of other vegetative structural components between burnt and unburnt woodlands, six months after a prescribed burn; that the fire has resulted in no change in the seedling emergence of lippia seeds stores in the soil seed bank; and, that the fire has resulted in no change of pseudo-species (not taxonomically identified species) richness within the seed bank.

Ten sites, (5 burnt, 5 unburnt) were sampled within each of the two woodlands: Eucalyptus camaldulensis and Eucalyptus populnea, six months after a prescribed burn. At each site, a 500 m2 quadrat was established to determine general disturbance measures (using a 0–4 scoring method) and the abundance and percentage cover of vegetative structural components. Within each 500 m2 quadrat, the density of the following vegetative structural components were
measured: trees > 20 m; trees 10–20 m; trees < 10 m; standing stags > 20 m; standing stags 10–20 m; standing stags < 10 m; stumps; logs 6–13 cm; logs 13–35 cm; logs 35–90 cm; and logs 90–150 cm. The percent cover of each of the following vegetative structural components was also
measured: trees; stags; stumps; logs; grasses/sedges; herbs/forbs; lippia; lippia litter; fine litter; bare ground. Within each 500 m2 quadrat, eight 70 cm2 sub-quadrats were placed along a 16 m transect to determine the cover abundance of lippia, grasses and forbs at a finer scale. Soil samples were also collected at each site for the glasshouse seed germination trial. Samples were
kept in the glasshouse for 14 weeks to determine total germination and pseudo-species richness of each site and treatment. Independent T-tests determined whether there were any significant differences of variables between treatments. The Levene’s Test for Homogeneity was used to
determine homogeneity.

There were no significant differences in the abundance and cover of lippia or vegetation structural components between burnt and unburnt woodlands, six months after a prescribed burn at either the broad (500 m2) or finer scale (70 cm2) (T-test, p > 0.05). The only exception to this finding was a significant difference in forb cover between burnt and unburnt Eucalyptus populnea woodlands (T-test, p < 0.05). There were no significant differences in seedling emergence or pseudo-species richness between burnt and unburnt treatments within each
woodland (T-test, p > 0.05).

This research shows that fire may not be a suitable control method for lippia invasion. The results found for structural components and the seedling germination trial were consistent with previous literature. Lippia’s response to fire in this study and the lack of positive effect that fire had on the invasive weed at St Ruth Reserve, has begun to fill an identified knowledge gap in the control methods for lippia. This study shows that fire may not be a useful management tool for lippia.


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Item Type: Thesis (Non-Research) (Honours)
Item Status: Live Archive
Additional Information: Bachelor of Science (Honours) thesis.
Faculty / Department / School: Current - Faculty of Health, Engineering and Sciences - School of Agricultural, Computational and Environmental Sciences
Supervisors: Le Brocque, Andy; Reardon-Smith, Kate
Date Deposited: 23 Apr 2015 05:03
Last Modified: 23 Apr 2015 05:03
Uncontrolled Keywords: fire management; riparian woodland; lippia; Phyla canescens
Fields of Research : 05 Environmental Sciences > 0501 Ecological Applications > 050103 Invasive Species Ecology
05 Environmental Sciences > 0502 Environmental Science and Management > 050209 Natural Resource Management
05 Environmental Sciences > 0502 Environmental Science and Management > 050202 Conservation and Biodiversity
URI: http://eprints.usq.edu.au/id/eprint/27160

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