Fire adaptations
Fire adaptations are traits of plants and animals that help them survive wildfire or to use resources created by wildfire. These traits can help plants and animals increase their survival rates during a fire and/or reproduce offspring after a fire. Both plants and animals have multiple strategies for surviving and reproducing after fire. Plants in wildfire-prone ecosystems often survive through adaptations to their local fire regime. Such adaptations include physical protection against heat, increased growth after a fire event, and flammable materials that encourage fire and may eliminate competition.
For example, plants of the genus Eucalyptus contain flammable oils that encourage fire and hard sclerophyll leaves to resist heat and drought, ensuring their dominance over less fire-tolerant species. Dense bark, shedding lower branches, and high water content in external structures may also protect trees from rising temperatures. Fire-resistant seeds and reserve shoots that sprout after a fire encourage species preservation, as embodied by pioneer species. Smoke, charred wood, and heat can stimulate the germination of seeds in a process called serotiny. Exposure to smoke from burning plants promotes germination in other types of plants by inducing the production of the orange butenolide.
Fires have also allowed for surviving species to create adaptations post-fire. This allows for better survival post-fire and furthers establishment. Adaptations as an example for boreal forests can include thick bark and post-fire flowering that is directly linked to fires. Other examples of species outside of plants and trees allow for further adaptation post-fire to survive and regenerate their population. This allows for better dispersal and new dispersal patterns to create a more stable environment. Vegetation, as an example, showed that it had greater gene flow than when unburnt and undisturbed.
Plant adaptations to fire
Unlike animals, plants are not able to move physically during a fire. However, plants have their own ways to survive a fire event or recover after a fire. The strategies can be classified into three types: resist, recover, and recruit. Fire plays a role as a filter that can select different fire response traits.Resist
Thick bark
Fire impacts plants most directly via heat damage. However, new studies indicate that hydraulic failure kills trees during a fire in addition to fire scorching. High temperature cuts the water supply to the canopy and causes the death of the tree. Fortunately, thick bark can protect plants because they keep stems away from high temperature. Under the protection of bark, living tissue won't have direct contact with fire and the survival rate of plants will be increased. Heat resistance is a function of bark thermal diffusivity and bark thickness. Thick bark is common in species adapted to surface or low-severity fire regimes. On the other hand, plants in crown or high-severity fire regimes usually have thinner barks because it is meaningless to invest in thick bark without it conferring an advantage in survivorship.Self-pruning branches
Self-pruning is another trait of plants to resist fires. Self-pruning branches can reduce the chance for surface fire to reach the canopy because ladder fuels are removed. Self-pruning branches are common in surface or low-severity fire regimes.Recover
Epicormic buds
are dormant buds under the bark or even deeper. Buds can turn active and grow due to environmental stress such as fire or drought. This trait can help plants to recover their canopies rapidly after a fire. For example, eucalypts are known for this trait. The bark may be removed or burnt by severe fires, but buds are still able to germinate and recover. This trait is common in surface or low-severity fire regimes.Lignotubers
Not all plants have thick bark and epicormic buds. But for some shrubs and trees, their buds are located below ground, which are able to re-sprout even when the stems are killed by fire. Lignotubers, woody structures around the roots of plants that contains many dormant buds and nutrients such as starch, are very helpful for plants to recover after a fire. In case the stem was damaged by a fire, buds will sprout forming basal shoots. Species with lignotubers are often seen in crown or high-severity fire regimes.Clonal spread
Clonal spread is usually triggered by fires and other forms of removal of above-ground stems. The buds from the mother plant can develop into basal shoots or suckers from roots some distance from the plant. Aspen and Californian redwoods are two examples of clonal spread. In clonal communities, all the individuals developed vegetatively from one single ancestor rather than reproduced sexually. For example, the Pando is a large clonal aspen colony in Utah that developed from a single quaking aspen tree. There are currently more than 40,000 trunks in this colony, and the root system is between 9,000 and 80,000 years old.Recruit
Serotiny
is a seed dispersal strategy in which the dissemination of seeds is stimulated by external triggers rather than by natural maturation. For serotinous plants, seeds are protected by woody structures during fires and will germinate after the fire. This trait can be found in conifer genera in both the northern and southern hemispheres as well as in flowering plant families. Serotiny is a typical trait in the crown or high-severity fire regimes.Fire stimulated germination
Many species persist in a long-lived soil seed bank, and are stimulated to germinate via thermal scarification or smoke exposure.Fire-stimulated flowering
A less common strategy is fire-stimulated flowering.Dispersal
Species with very high wind dispersal capacity and seed production often are the first arrivals after a fire or other soil disturbance. For example, fireweed is common in burned areas in the western United States.Plants and fire regimes
The fire regime exerts a strong filter on which plant species may occur in a given locality. For example, trees in high-severity regimes usually have thin bark while trees in low-severity regimes typically have thick bark. Another example will be that trees in surface fire regimes tend to have epicormic buds rather than basal buds. On the other hand, plants can also alter fire regimes. Oaks, for example, produce a litter layer which slows down the fire spread while pines create a flammable duff layer which increases fire spread. More profoundly, the composition of species can influence fire regimes even when the climate remains unchanged. For example, the mixed forests consists of conifers and chaparral can be found in Cascade Mountains. Conifers burn with low-severity surface fires while chaparral burns with high-severity crown fires. Ironically, some trees can "use" fires to help them to survive during competitions with other trees. Pine trees, for example, can produce flammable litter layers, which help them to take advantage during the completion with other, less fire adapted, species.Grasslands in Western Sabah, Malaysian pine forests, and Indonesian Casuarina forests are believed to have resulted from previous periods of fire. Chamise deadwood litter is low in water content and flammable, and the shrub quickly sprouts after a fire. Cape lilies lie dormant until flames brush away the covering and then blossom almost overnight. Sequoia rely on periodic fires to reduce competition, release seeds from their cones, and clear the soil and canopy for new growth. Caribbean Pine in Bahamian pineyards have adapted to and rely on low-intensity, surface fires for survival and growth. An optimum fire frequency for growth is every 3 to 10 years. Too frequent fires favor herbaceous plants, and infrequent fires favor species typical of Bahamian dry forests.