Subalpine plants show short-term positive growth responses to experimental warming and fire
Frith C. Jarrad A D E , Carl-Henrik Wahren B , Richard J. Williams C and Mark A. Burgman AA School of Botany, University of Melbourne, Parkville, Vic. 3010, Australia.
B Centre for Applied Alpine Ecology, LaTrobe University, Melbourne, Vic. 3086, Australia.
C CSIRO Sustainable Ecosystems, Winnellie, NT 0822, Australia.
D Current address: School of Mathematical Sciences, Queensland University of Technology, Brisbane, Queensland 4001, Australia.
E Corresponding author. Email: frithjarrad@qut.edu.au
Australian Journal of Botany 57(6) 465-473 https://doi.org/10.1071/BT09050
Submitted: 3 March 2009 Accepted: 20 September 2009 Published: 9 November 2009
Abstract
Climate warming has the potential to directly affect plant growth rates by accelerating plant processes, and through intermediate affects associated with increased length of the growing season and changes to soil processes. Alpine and subalpine ecosystems may be particularly vulnerable to climate warming because species are adapted to a cold environment and have limited upslope refugia in Australia. In the present study, the vegetative growth of seven subalpine open-heath species was examined in response to 3 years of warming and a wildfire. The warming experiment was established in late 2003 on the Bogong High Plains, Australia, using the protocols of the International Tundra Experiment (ITEX). During the growing seasons (snow-free periods) in 2004/2005 and 2005/2006 leaves and stems were monitored on common or widespread species from each of the major vascular plant growth forms. Plants were monitored inside and outside passively warmed open-topped chambers, at sites that were burnt in early 2003 and sites that escaped fire. In the short-term, warming had significant positive relationships with relative growth rates of three species, including Celmisia pugioniformis (forb; P = 0.09), Carex breviculmis (graminoid; P = 0.004) and Asterolasia trymalioides (shrub; P = 0.02). Burning had significant positive effects (P < 0.05) on the relative growth rates of two of these species, C. pugioniformis and C. breviculmis, as well as for Plantago euryphylla, Poa hiemata and Pimelea alpina. For P. euryphylla and P. alpina, the interaction of warming and burning showed significant relationships with relative growth rates, a negative relationship in P. euryphylla (P = 0.03) and a positive relationship in P. alpina (P = 0.07). Year and season were also found to affect the relative growth rates of most species (P < 0.05). These findings agree with previous northern hemisphere ITEX and other warming experiment results; that is, warming has a positive effect on species’ growth responses. In the present study, it is likely that continued climate warming may result in positive growth responses in other subalpine species across growth forms. Our findings emphasise the value of examining multiple species in climate-change studies.
Acknowledgements
This research was funded through an Australian Research Council Linkage Grant (LP0348897), the Department of Sustainability and Environment, Parks Victoria, CSIRO, ESLink Services Pty Ltd, and Mt Hotham Resort Management. We would like to thank Carolyn Blomley, Cherie Campbell, Deborah Cargill, Katherine Giljohann, Danielle Ryan, Paul Smart, Clare Warren and Emma Warren for their assistance in collecting field data. We would also like to thank Warwick Papst for his role in facilitating the ITEX project, Dr Sama Low Choy for statistical advice, and reviewers for comments on this manuscript.
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