Pasture composition in cleared and uncleared woodlands
Kamaljit Kaur A C , David J. Midmore A , Rajesh K. Jalota B and Nanjappa Ashwath AA Plant Sciences Group, Primary Industries Research Centre, Central Queensland University, Rockhampton, Qld 4702, Australia.
B Centre for Environment Management, Central Queensland University, Emerald, Qld 4720, Australia.
C Corresponding author. Current address: School of Business, James Cook University, Townsville, Qld 4812, Australia. Email: kamaljit.kaur@jcu.edu.au
Australian Journal of Botany 54(5) 459-470 https://doi.org/10.1071/BT05174
Submitted: 10 October 2004 Accepted: 19 December 2005 Published: 3 August 2006
Abstract
Land clearing in Queensland is often practised to enhance pasture production, and hence, increase financial returns from beef production. The benefits of clearing have been quantified in terms of short-term gains in pasture yield but have not adequately accounted for possible medium- or longer-term impediments that may be attributed to clearing. Therefore, impacts of clearing and the subsequent sowing of exotic grasses such as Cenchrus ciliaris L. on pasture composition and production were studied. To achieve this, paired sites were selected representing cleared and uncleared pastures across three different times since clearing (i.e. 5, 11–13 and 33 years since clearing) for the three dominant tree communities of central Queensland (i.e. Eucalyptus populnea F.Muell. (poplar box), E. melanophloia F.Muell. (silver-leaved ironbark) and Acacia harpophylla F.Muell. ex. Benth. (brigalow)). The results demonstrated that species diversity declined with clearing and sowing of exotic pastures. Species diversity and pasture production were negatively related. Although pasture yield was 2–3 times greater 13 years after clearing of E. populnea and A. harpohylla, the gains in pasture yield were not consistent over time, yields being only 1.5 times greater after 33 years of clearing. In E. melanophloia, an increase in the yield of only 1.5–1.8 times occurred 5 years after clearing compared with uncleared pastures, whereas 33 years after clearing, yield was 3/4 of that in uncleared pastures. The initial gains in pasture yield were accompanied by a loss of plant diversity that may affect ecosystem functions such as nutrient cycling or soil mineralisation, and the longer-term production gains.
Acknowledgments
We thank the landholders Mrs and Mr Spooner for permission to conduct this research on their property. The laboratory space and equipment provided by the Department of Natural Resources and Mines and the Department of Primary Industries at Emerald is gratefully acknowledged. We specially thank Dr Rhonda Melzer (Environmental Protection Agency (EPA), Rockhampton) and Ms Melinda Fletcher (EPA, Emerald) for their help in identification of plant species. Funds for this research were provided by Central Queensland University, Queensland. We acknowledge the improvements to the manuscript by the anonymous reviewers.
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