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RESEARCH ARTICLE
Contents Vol 56(4)

Comparative ecology of two co-occurring floodplain plants: the native Sporobolus mitchellii and the exotic Phyla canescens

Ben Taylor A B D and George G. Ganf C
+ Author Affiliations
- Author Affiliations

A School of Earth and Environmental Sciences, The University of Adelaide, SA 5005, Australia.

B Present address: Department for Environment and Heritage, PO Box 1046, Mount Gambier, SA 5290, Australia.

C Co-operative Research Centre for Freshwater Ecology.

D Corresponding author. Email: taylor.ben@saugov.sa.gov.au

Marine and Freshwater Research 56(4) 431-440 https://doi.org/10.1071/MF04196
Submitted: 27 July 2004  Accepted: 1 April 2005   Published: 27 June 2005

Abstract

In the northern Murray–Darling Basin (MDB), Australia, the displacement of native floodplain grasses by Phyla canescens (Lippia), an exotic herb, coincided with a reduced frequency of floodplain inundation owing to river regulation. Although river regulation and P. canescens occur in the southern MDB, P. canescens abundance has not increased significantly since 1988. This work reports on the current distribution of P. canescens and the native grass Sporobolus mitchellii on the lower River Murray. It demonstrates that there are significant differences in the edaphic characteristics of sites occupied by the two species and co-occurrence is rare. To explain this observation, two factors were investigated: the resilience of S. mitchellii to invasion by P. canescens and the response of both species to artificial spring floods. At initial densities of >25%, S. mitchellii exhibited strong resilience to invasion by P. canescens. The growth response of both species to spring floods was similar. However, P. canescens reproduced asexually when inundated and, on exposure, exhibited a root distribution that would enhance its capacity to survive future droughts. In contrast, S. mitchellii was more tolerant of low soil moisture than P. canescens. The re-introduction of spring floods could favour the expansion of P. canescens.

Extra keywords: environmental flows, plant–plant interactions, riparian vegetation, river health, weeds.


Acknowledgments

The Murray–Darling Division, Department of Water, Land and Biodiversity Conservation provided research funding. The Environmental Analysis and Research Unit, Environmental Geographic Information, Department for Environment and Heritage provided vegetation survey data. CSIRO Land and Water provided floodplain soil and groundwater data and flooding data based on the Floodplain Inundation Model, Murray–Darling Basin Commission and River Murray Catchment Water Management Board.


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