Life after fire: smoke and ash as germination cues in ericads, herbs and graminoids of northern heathlands
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Question: What is the impact of the fire cues smoke and ash on seed germination of important functional groups in the heathland system, namely ericads, herbs and graminoids? We predict that if germination from heathland seed banks is in part regulated by fire cues, there should be stronger responses to fire cue treatments in seed bank samples taken from heath that has not been recently burned in comparison with samples taken from newly burned heath, where seed banks have been exposed to the same cues in situ.
Location: Lygra, Lindås commune,western Norway.
Methods: The efficacy of smoke, charred wood, ash and heat in promoting germination has been documented in a wide range of species and systems, but relatively little work has been done on fire-related cues in northern European heathlands under anthropogenic fire regimes. We studied fire experimentally by testing the effects of aqueous smoke solution, ash and a combination of the two treatments, on the germination of graminoids, herbs and ericads. A greenhouse germination trial compared seed banks from old heath (28 yr since the last fire) with seed banks from newly burned heath (burned the previous year), wherewe expected that fire-cued germination had already occurred.
Results: We found that both ericads and graminoids responded to fire cues, whereas herbs did not. In line with our predictions, responses were stronger in the old heath than in the young heath. Further, the smoke treatment is a more effective cue than ash across all functional groups.
Conclusions: The prevalence of positive fire cue responses across functional groups underscores the importance of fire in the ecology of these heathlands, and hence of burning as a central tool for their management. The finding that the germination response is stronger in na€ıve seed banks than in seed banks that have already been exposed to recent fire cues through in situ fires further supports the role of fire in the successional dynamics of these heathlands.