Fire adapted species possess inherited traits that allow
them to enhance their survivorship or fitness during or after a fire. Fire
adaptations are derived from a long history of plant species evolving in
ecosystems with fire regimes. In order for a trait to be considered a fire
adaptation, fire must be the main selective force that allowed that trait to
thrive within a species. There are many selective forces that could’ve promoted
traits that improve survivorship or fitness in fire, which makes identifying a
fire adaptation a difficult process. Today, there are many traits that are
generally accepted as fire adaptations and are managed as such.
1.
Thick bark is considered to be a fire adaption
because it can prevent the vascular cambium form being damaged. The bark acts
like a medium that transfers heat from the fire to the cambium. If the bark is
thick, it will take more energy to transfer enough heat to cause damage. This
fire adaption will increase survivorship when exposed to low or possibly
moderate severity levels of fire. A high severity fire will likely produce
enough heat to damage the cambium and engulf the tree. Areas will low to
moderate fire intensity regimes will likely select for trees with thicker bark
since trees without this trait could have lower survivorship.
2.
Another fire adaptation could be plants with
growing points below the soils surface. These plants have the ability to
surface low severity fires because the soil acts like an insulator and protects
the growing points below the surface. These plants can successfully remain
established after a fire. High or moderate intensity fires can heat up the soil
to a point of damaging the plant beyond recovery.
Matt,
ReplyDeleteGreat post. Ponderosa exhibit the second trait you mentioned in that they have deep root systems that can typically sustain surface fires. They also have the first trait you mentioned. Some other adaptations (or exaptations) that can be seen in fire-adapted species have to do with shorter life cycles in order to drop seeds in a more timely manner, especially if frequent fires are seen within the ecosystem. I feel that this is an example of an adaptation versus an exaptation because while the trait may have been evolved, it seems to be more of a response to the environmental demands the species faces.
Thanks,
Ashley
Ashley,
DeleteI think that frequent fire would be a strong selective pressure that promotes fire adaptations. I really like the short life cycle example that you provided. Figuring out if a trait is an adaptation or a exaptation is definitely not easy and requires knowledge of fire regimes and selection forces that the trait responds well to. I think its important that the traits are identified along with what fire regimes they do well in and less important to figure out if the trait is truly a fire adaptation or exaptation.