Seedling recruitment of the exotic grass Andropogon gayanus (Poaceae) in northern Australia
Trish A. Flores A , Samantha A. Setterfield A B and Michael M. Douglas AA School of Sciences, Charles Darwin University, Darwin, NT 0909, Australia.
B Corresponding author. Email: samantha.setterfield@cdu.edu.au
Australian Journal of Botany 53(3) 243-249 https://doi.org/10.1071/BT03154
Submitted: 16 October 2003 Accepted: 14 December 2004 Published: 26 May 2005
Abstract
Andropogon gayanus Kunth. (Gamba grass), a tall perennial grass from Africa, is invading savanna ecosystems in northern Australia. This study investigated A. gayanus recruitment to determine the habitats at risk of invasion and to provide recommendations for its management. A. gayanus is able to establish and spread into new areas because of its high seed production (averaging 70 000 seeds m–2) and ability to establish across a range of habitats: from open woodlands on relatively dry lateritic soils to the more closed forests on black soil of the floodplain margins. Seedling emergence occurred in the absence of soil cultivation, although soil cultivation did increase emergence in the wetter habitats (Melaleuca uplands and floodplain margins). Seedling survival was high in the savanna (~90%) but low in the wetter habitats owing to wet-season inundation. A seed longevity trial based on burying seed in the field and retrieving between 1 and 12 months after burial showed that less than 1% of seeds survived in the seedbank after 12 months. Effective control programs are needed immediately because of the vast area and range of habitats in northern Australia that could potentially be invaded by A. gayanus. Management that can limit site disturbance and seed production, and can incorporate follow-up control for one to two years, should be an important part of an A. gayanus control strategy.
Acknowledgments
We acknowledge the funding and support provided by the Department of Infrastructure, Planning and Environment (formerly PWCNT), particularly C. Wilson, B. Panton, K. Tschirner, J. Abbott, B. Harwood, and the Mary River District Rangers. We also thank the staff at the Department of Business, Infrastructure, Research and Development for input and advice, particularly A. Cameron, B. Ross and A. Simonato. Thanks also go to P. Wurm, C. Devonport, J. Brock, G. Cook, A. Clark, N. Rossiter and M. Welch for advice and assistance. We appreciate the valuable comments made by R. Williams, D. Bowman, A. Andersen and the NTU Ecology lab. Special thanks also go to the many field volunteers.
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