Effects of soil temperature regimes after fire on seed dormancy and germination in six Australian Fabaceae species
Victor M. Santana A F , Ross A. Bradstock B , Mark K. J. Ooi C D , Andrew J. Denham C , Tony D. Auld C and M. Jaime Baeza A EA Fundación de la Generalitat Valenciana Centro de Estudios Ambientales del Mediterráneo (CEAM), Parque Tecnológico Paterna, C/Charles Darwin, 14. 46980 Valencia, Spain.
B Centre for Environmental Risk Management of Bushfires, Institute for Conservation Biology and Environmental Management, University of Wollongong, NSW 2522, Australia.
C Department of Environment, Climate Change and Water NSW, PO Box 1967, Hurstville, NSW 2220, Australia.
D Department of Animal and Plant Sciences, University of Sheffield, Sheffield S10 2TN, UK.
E Departamento de Ecología, Universidad de Alicante, Ap 99. 03080 Alicante, Spain.
F Corresponding author. Email: [email protected]
Australian Journal of Botany 58(7) 539-545 https://doi.org/10.1071/BT10144
Submitted: 4 June 2010 Accepted: 18 August 2010 Published: 27 October 2010
Abstract
In addition to direct fire cues such as heat, smoke and charred wood, the passage of fire leads indirectly to changes in environmental conditions which may be able to break physical dormancy in hard-coated seeds. After a fire, the open canopy and the burnt material lying on the surface alter the thermal properties of the soil, resulting in elevated soil temperatures for long periods of time. We simulated daily temperature regimes experienced at different depths of soil profile after a summer fire. Our aim was to determine whether these temperature regimes and the duration of exposure (5, 15 and 30 days) play an important role breaking physical seed dormancy in six legumes from south-eastern Australia. Our results showed that simulated temperature regimes break seed dormancy. This effect is specially pronounced at temperatures that are expected to occur near the soil surface (0–2 cm depth). The duration of exposure interacts with temperature to break dormancy, with the highest germination rates reached after the longest duration and highest temperatures. However, the germination response varied among species. Therefore, this indirect post-fire cue could play a role in the regeneration of plant communities, and could stimulate seedling emergence independent of direct fire cues as well as in interaction with direct cues.
Acknowledgements
We thank Fiona Thomson for providing seeds for this experiment. V. M. Santana was supported by a FPU grant awarded by the Spanish Ministry of Education and Science and by the Consolider-Ingenio 2010 (GRACCIE CSD2007–00067) and FIREMED (AGL2008–04522/FOR) projects. CEAM is supported by the Generalitat Valenciana and Fundación Bancaja.
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