When forests burn, trees die. It’s a fact. Particularly when hot fires occur in dense fuels, cambium cooks and needles fry. Conifers are particularly flammable and can go up in a spectacular crown fire. The resulting sea of black dead stems causes some people to think we must do something immediately. Not so fast. Catch your breath.
Post-fire recovery is a complicated process; it requires time and care to help the forest heal as best as possible. Dead trees have many important roles. They offer some shade to seedlings trying to become established. Roots, although dead, provide soil stability. When trees fall, (which can occur immediately, or much, much later), the downed logs help hold the soil in place, provide decaying organic material and habitat for many species such as chipmunks, small birds and snakes. Small mammals are particularly important to forest recovery because they help disperse plant seeds and fungal spores that help inoculate soils with important microorganisms that release nutrients into the system.
At many levels, dead trees are an integral component of the regenerative process after a fire.
In forests, dead trees are critical habitat for many species: when standing, they provide nesting and feeding sites for woodpeckers and other cavity-dependent species, as well as perches for song birds. Down logs provide important ground-level habitat. Dead trees are created in pulses over time: in mature forests, single or small groups of trees are killed by fungus, wind, insects or competition between trees. Large numbers of trees can be killed all at once, too, such as in a fire. Some birds, such as the black-backed and three-toed woodpeckers, are specifically adapted to utilize fire-killed trees. These dead trees will often stand for many decades and blackened stems can be found in many mature forest stands.
Thick barked trees such as Douglas fir and ponderosa pine can survive if the fire doesn’t get so hot that it burns the fine roots or kills all of the buds and cambium. These survivors are the scattered trees we see in natural, or thinned and burned, dry forests. Sometimes, trees that appear to be dead will recover, while other trees that appear ok will succumb to insects. It is all part of the natural order.
Salvage logging can damage fragile soils and accelerate erosion and weed infestation on disturbed, fragile soils. Forest recovery is inhibited by removing dead trees that could help stabilize the soil and provide habitat. Cutting dead trees may be necessary to protection infrastructure such as buildings or along roads where falling trees could pose safety hazards. Cutting these may also be a way to gather at least some monetary value from trees otherwise destined for harvest. However, dead trees generally do not need to be removed to help the forest recover.
Some manipulations can help recovery. Removing the tops of tall dead trees may help them stand longer by removing some of the weight on the upper stem. It may also introduce heart rot more quickly to soften the stems for woodpeckers. Laying small diameter trees in dense stands across steep slopes can help reduce erosion if the stems are lying completely against the soil. Very dense stands can have extensive down, dead wood making for intense re-burns decades later, and some fuel reduction may be beneficial there. But, overall, the forest recovers best when the dead trees remain, especially the large, and nature is allowed to take its course.
Dead trees are beautiful and stark reminders of the fury and healing properties of nature. Ponder their grandeur in the wake of fire and leave them standing as functional landmarks to the power of nature.
For information about forest stewardship on private lands, and opportunities for cost-share thinning projects to help protect property from the next event (remember: it’s not a matter of if, but of when), please visit the Washington State Department of Natural Resources Small Forest Landowner Office at www.dnr.wa.gov/sflo. There you will find information on programs and local contacts.
by Ken Bevis, Stewardship Biologist, Washington Department of Natural Resources