Will my tree live? Assessing postfire survivability

Extensive research on the fate of fire-damaged trees provides guidance for assessing survival based on post-fire observations of three key factors: crown scorch, bark char and root damage.

Vulnerability to fire damage depends on tree species and size. Larger trees with thicker bark and larger amounts of foliage can generally withstand more damage than thin-barked species.Thick-barked species such as Douglas-fir, ponderosa pine, western larch and incense cedar are resistant to fire damage. High levels of crown injury are typically required to kill thick-bark trees. Thin-barked species such as western hemlock, western redcedar, spruce and lodgepole pine are easily killed by fire, even with little crown damage.

It may take several years for trees to die from fire-related injury. Trees that survive direct injuries from fire often become more vulnerable to secondary factors, such as insect infestations and drought stress.

Assessing damage based on bark char

This involves examining the bole, base and roots. Bark char on thin-bark species is a reliable indicator of cambium death, but it is not as reliable on species with thick bark. Cambium is the living tissue under the bark.

Heavy–severe bark char damage

• Fire penetrates bark, but not necessarily to the wood.
• Species loses its bark characteristics.
• Bark smoothed; all ridges are gone.
• Considerable or deep duff and woody debris consumption around base.
• Many roots exposed and charred due to combustion of organic matter.

Moderate–significant bark char damage

• Bark is uniformly black except some inner fissures; species bark characteristics are still discernable.
• Some organic matter consumed in the burned area.
• Some roots may be exposed and charred.

Light–minor bark char damage

• Bark is not completely blackened; species bark characteristics obvious; edges of bark plates charred.
• Little duff or organic matter consumed.
• Roots not exposed or charred.

Tolerance for risk

Decisions about whether or not to remove injured trees depend upon your tolerance for risk. You may have a low tolerance for risk, where it is essential to avoid leaving trees that may die (for example, where damaged trees could pose a threat to safety or property).

You may have a higher tolerance for risk of tree death in forest settings where your goal is to save any trees that may live.

Longer-term outlook

Damaged trees that survive a fire can recover and live for many years. However, fire scars can create entry points for wood decay, increasing the risk of stem breakage over time. To prevent this, trees must regain enough vigor to grow new wood around the wound and seal out decay.

Interestingly, even trees with partial decay can provide valuable habitat, serving as excellent wildlife trees.

See the tree assessment criteria below for major conifer species in Oregon and Washington. For help assessing fire injury on your trees, contact your local OSU Extension office or the Oregon Department of Forestry.

Tree assessment criteria

If your trees have been damaged by fire, deciding whether to remove them or give them a chance to recover depends on your goals and how much risk you're comfortable with, especially if the trees are near structures or frequently used areas.