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Environmental factors influencing the establishment, height and fecundity of the annual grass Sorghum intrans in an Australian tropical savanna

Published online by Cambridge University Press:  30 March 2010

Kenneth A. Scott ,
Samantha A. Setterfield ,
Michael M. Douglas  and
Alan N. Andersen
Kenneth A. Scott*
Affiliation:
School of Environmental and Life Sciences, Charles Darwin University, Darwin, Northern Territory, 0909, Australia Bushfire Cooperative Research Centre, East Melbourne, Victoria, Australia (www.bushfirecrc.com)
Samantha A. Setterfield
Affiliation:
School of Environmental and Life Sciences, Charles Darwin University, Darwin, Northern Territory, 0909, Australia School for Environmental Research, Charles Darwin University, Darwin, Northern Territory, 0909, Australia
Michael M. Douglas
Affiliation:
Bushfire Cooperative Research Centre, East Melbourne, Victoria, Australia (www.bushfirecrc.com) School for Environmental Research, Charles Darwin University, Darwin, Northern Territory, 0909, Australia
Alan N. Andersen
Affiliation:
Bushfire Cooperative Research Centre, East Melbourne, Victoria, Australia (www.bushfirecrc.com) CSIRO Sustainable Ecosystems, PMB 44, Winnellie, Northern Territory, 0822, Australia
*
1Corresponding author. Department of Regional Development, Primary Industry, Fisheries and Resources, PO Box 159, Tennant Creek, NT, 0861Australia. Email: kenneth.scott@hotmail.com
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Abstract:

Environmental factors influencing grass establishment and performance in tropical savannas are poorly understood, particularly in relation to disturbance. We describe a seed sowing experiment that examined the effects of fire regime, canopy cover and litter cover on the emergence, establishment, height and fecundity (seed production) of the regionally dominant annual grass Sorghum intrans in northern Australia. Establishment was significantly lower under the woody canopy compared with canopy gaps, and where seeds were sown on a layer of litter compared with bare soil. However, variation in fire regime had no significant effect on establishment or seed production. Additionally, a shade-house experiment was conducted to test the effects of litter on seedling emergence of S. intrans and six other grass species representative of the local flora (Pseudopogonatherum contortum, Sorghum plumosum, Chrysopogon latifolius, Eriachne triseta, Heteropogon triticeus and Alloteropsis semialata). All species showed reduced emergence when sown either above or below litter, compared with bare soil. Our results demonstrate the importance of the overstorey as a determinant of S. intrans abundance and savanna grass composition more generally, through its effect on establishment. The aversion of savanna grasses to litter (and S. intrans to canopy shading) supports the notion of savanna species being highly adapted to disturbance.

Keywords

canopy coverfire regimegrass dynamicslittermicrositesnorthern Australia
Type
Research Article
Information
Journal of Tropical Ecology , Volume 26 , Issue 3 , May 2010 , pp. 313 - 322
Copyright
Copyright © Cambridge University Press 2010

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