Few species possess true fire adaptation. Adaptation is the
result of derived traits to a specific environmental pressure. For a species to
be fire adapted, it must possess a feature borne only from the confluence of
its progenitors with fire events. That feature must have imparted superior
fitness to those ancestral plants which was then bequeathed to their offspring.
Out of many clever plant adaptations, perhaps only two might qualify as fire
adaptations: serotiny and smoke-assisted germination. The former needs fire to
melt resins which seal seeds within their cones, while the latter needs the
presence of smoke-vectored chemicals (NO2, karrikins, cyanohydrins) to break seed
dormancy and induce germination. Strictly speaking there are different degrees
of serotiny – weakly, strongly, facultative, or obligate – such that true fire
adaptation might be constricted to serotinous obligates. Species such as
Lodgepole pine (Pinus contorta) need
heat from fires around 115˚ – 140˚ F to melt resins that fuse the scales of the
cone shut.
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| Sealed Lodgepole pine cones. Photo by Benkman Lab, University of Wyoming |
Smoke induced germination is a widespread trait among the
families Asteraceae, Ericaceae, Poaceae, and Fabaceae. Fires which burn around
320˚ – 390˚ F produce water-soluble compounds which, combined with flushes of
fresh water, are thought to stimulate rapid germination in fire-affected
landscapes. The species Black-eyed Susan (Rudbeckia
hirta) and Coyote tobacco (Nicotiana
attenuata) have been identified as smoke-sensitive forbs.
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| Black-eyed Susan Photo by NRCS Plant Database |
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| Coyote tobacco Photo by Oregon State University |
Serotiny and smoke-assisted germination are useful adaptations
for re-populating fire-cleared landscapes. What better incentive for the next
generation to develop than on the heels of that which killed its parents? With
cues from smoke and heat, seeds can prime themselves for growth in the first clement
weather. Thus one can see that fire is a force capable not only of dealing
death, but facilitating life.
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| Germination of Lodgepole pine Photo by Benkman Labs, University of Wyoming |
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| Regrowth after fire Photo by US Geological Survey |
Excellent array of adaptation examples! It is amazing to witness what follows a fire yet the fire can be a frightening experience. And there are so many benefits to the adaptations that are necessary processes in a healthy environment.
ReplyDeleteAccurate, thorough, and it covers a lot. I enjoyed reading it as well as you have an informative way of writing. The 4 images lends a nice bit of color as well.
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