Seed size and germination response: a relationship for fire-following plant species exposed to thermal shock

Hanley, M.E., Unna, J.E. and Darvil, B. (2003) Seed size and germination response: a relationship for fire-following plant species exposed to thermal shock. Oecologia, 134 (1), 18-22. (doi:10.1007/s00442-002-1094-2).

Abstract

Thermal shock is well known to be an important stimulus for the germination of soil-stored seeds in fire-prone plant communities. Nevertheless, while the overall germination response of different species is known to vary, the interaction between seed size and germination to a range of thermal-shock temperatures is poorly understood. This interaction may be important in regulating post-fire plant community establishment, since larger seeds are able to emerge from deeper within the soil profile than smaller seeds, and are therefore likely to be insulated against high above-ground temperatures by a deeper soil covering. In this experiment we examined how germination of eight co-occurring Western Australian fire-followers was influenced by thermal shock, and whether germination was significantly correlated with seed size. We found that small-seeded species not only showed enhanced germination at higher temperatures, but that their ability to germinate at higher temperatures was also greater than that displayed by larger-seeded species. These findings suggest that while seed size may be a useful general predictor of post-fire recruitment success, under different fire regimes the interaction between seed size, maximum seedling emergence depth, and the ability to withstand different thermal-shock temperatures is complex and may confound recent predictive models.

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