Wildfire Concepts Wildfire









Fire and the Ecosystem

Nowadays, it is generally agreed upon that total fire suppression will only lead to higher and higher fuel levels; which, in turn, greatly increases the likelihood of a large fire occurring.  Fire is now viewed as a necessary occurrence in Yellowstone in order to encourage new growth and diversity in the forests and meadows of the park (Knight 1991).

Lodgepole pine trees today still show scars from the 1988 fires in Yellowstone.
The 1988 fires in Yellowstone National Park burned approximately one-third of the park (Baskin 1999), approximately 250,000 hectares in the park and the surrounding lands (Turner et al. 1994).  Many people saw this as a disastrous wave of destruction.  However, by the first spring after the fires, new grasses had already grown half as tall as an elk in certain areas.  Burned meadows displayed a colorful array of wildflowers, including yellow arnica, mountain hollyhock, and blue lupine (Robbins 1998).  People began to see that fire did not simply kill; it encouraged new growth. 

Wildfire creates a patchwork of affected areas.  Each level of burning can be assigned a burn class:  unburned, light surface burn, severe surface burn, and crown fire.  Larger burns (larger areas that have been burned) are less likely than smaller burns to be dominated by a single burn class.  Those areas that were not burned may serve as a source of renewal (Turner et al. 1994).

Many trees house their seeds in their canopy as well as in the soil.  High severity fires will most likely burn a significant portion of an area’s seedbank in the soil and the canopy.  In a lightly burned area, plants can often resprout from surviving roots and rhizomes.  In a severely burned area, plants depend on surrounding or nearby plants as a seed source to initiate new growth.  As much burning occurs in patches, with a combination of all burn classes, there is usually an unburned or lightly burned area close to a severely burned area which can serve as the seed source for the severely burned area.  Plants will most likely resprout faster in smaller burn areas.  If less area is burned, any burned plants will be closer to a seed source than plants in the heart of a large, severely burned area.  Thus for larger burn areas, opportunistic or invader species may be able to move into the area and establish themselves before the burned plants have time to resprout (Turner et al. 1994).

Some trees have their own form of protection against fire.  For example, Lodgepole pine (Pinus contorta) produces serotinous cones.  These cones are sealed shut with resin and will only open to release the seeds after being heated to a certain temperature (Turner et al. 1997).  Due to this particular adaptation, Lodgepole pine is one of the first trees to resprout in Yellowstone.  This is also why approximately 80% of the trees in Yellowstone are Lodgepole pine (Craighead 1991, Turner et al.1994).

A serotinous cone burns on the forest floor.