Disentangling the role of heat and smoke as germination cues in Mediterranean Basin flora

Abstract

BACKGROUND AND AIMS: The role of fire as a germination cue for Mediterranean Basin (MB) plants is still unclear. The current idea is that heat stimulates germination mainly in Cistaceae and Fabaceae and that smoke has a limited role as a post-fire germination cue, in comparison with other Mediterranean-type ecosystems (MTEs), suggesting that fire-stimulated germination is less relevant in the MB than in other MTEs. However, recent studies showed that the assembly of Mediterranean plant communities is strongly driven by post-fire germination, suggesting an important role for fire as a germination cue. We hypothesize that both heat and smoke have important effects on the different post-fire recruitment processes of MB species (e.g. level and rate of germination and initial seedling growth). METHODS: To ascertain the role of heat and smoke in the post-fire germination response of MB woody plants, a germination experiment was performed with seven heat and two smoke treatments on 30 MB woody species from seven different families, including species with water-permeable seeds and species with water-impermeable seeds. KEY RESULTS: Heat stimulated the germination (probability and rate) of 21 species and smoke in eight species, out of the 30 species studied. In addition, six species showed enhanced initial seedling growth after the smoke treatments. CONCLUSIONS: The results suggest that both heat and smoke are important germination cues in a wide range of MB woody species and that fire-cued germination in woody plants of the MB may be as important as in other MTEs.