PHYSIOLOGICAL ECOLOGY - ORIGINAL PAPER The interaction of temperature, water availability and fire cues regulates seed germination in a fire-prone landscape Paul Bengt Thomas Æ E. Charles Morris Æ Tony D. Auld Æ Anthony M. Haigh Received: 9 December 2008 / Accepted: 25 August 2009 Ó Springer-Verlag 2009 Abstract Ambient temperature and water availability regulate seasonal timing of germination. In fire-prone landscapes, the role of fire-related cues in affecting the range of temperatures and water potentials (ws) across which germination can occur is poorly known, especially in non-Mediterranean landscapes. We examined interactive effects of temperature (15 or 25°C), w (0 to -0.9 MPa), and fire-related cues (heat and smoke) on germination for seeds of three shrub species from fire-prone southeastern Australia. Incubation temperature affected germination of untreated seeds of Kunzea ambigua and Kunzea capitata (Myrtaceae) (reduction at 25°C), but germination was uniformly low in Epacris obtusifolia (Ericaceae). Decreasing w reduced germination across both incubation temperatures. Fire cues increased germination at both incubation temperatures and across ws, although in Kunzea the increase was smaller and occurred over a narrower range of ws at 25°C. Hydrotime analysis suggested that fire cues reduced the amount of water necessary for germina- tion of Kunzea seeds. Post-fire germination of the three study species may occur during the warm season, although it is reduced and confined to wet periods for the two Kunzea species. Warm season germination of the study species is consistent with a trade-off between the increased risk of failure of a cohort of seedlings, and benefits of early establishment of a cohort that may survive in an environ- ment with aseasonal rainfall. Keywords Heat  Smoke  Hydrotime  Water potential  Soil seed bank Introduction Many species regenerate from persistent soil-stored seeds in landscapes with frequently recurring but unpredictable stand-replacing fires. Germination of soil-stored seeds may be restricted to a short time following a fire, allowing seedlings to capture the increased available resources such as light, space and nutrients (Bond and van Wilgen 1996). In addition, inter-fire germination is likely to produce poor recruitment due to competitive effects of established plants and predation (Specht et al. 1958; Tozer and Bradstock 1997). Mechanisms for limiting germination to the imme- diate post-fire environment include fire-related germination cues such as heat and smoke (Keeley et al. 1985; Thomas et al. 2003). Post-fire germination may be restricted to seasons that are likely to result in adequate seedling survival (Vleeshouwers et al. 1995; Hilhorst 1998). Such germination in regions with Mediterranean climates is cued to provide maximum time Communicated by Dave Pyke. Electronic supplementary material The online version of this article (doi:10.1007/s00442-009-1456-0) contains supplementary material, which is available to authorized users. P. B. Thomas (&)  E. C. Morris Ecology and Environment Research Group, Hawkesbury Campus (K12), University of Western Sydney, Locked Bag 1797, Penrith South, DC 1797, Australia e-mail: p.thomas@uws.edu.au T. D. Auld Climate Change Science, Department of Environment and Climate Change (NSW), PO Box 1967, Hurstville, NSW 2220, Australia E. C. Morris  A. M. Haigh Centre For Plants and the Environment, Hawkesbury Campus, University of Western Sydney, Locked Bag 1797, Penrith South, DC 1797, Australia 123 Oecologia DOI 10.1007/s00442-009-1456-0