By Deborah Holt Williams
Forest fires, like the Las Conchas fire that raged through New Mexico in 2011, leave some trees charred and clearly dead. Other trees seem totally untouched and perfectly fine. But fires also leave many trees partially burned. What are the chances for these trees to survive?
Santa Fe National Forest Forestry Program Manager David Lawrence says that the rate of survival depends partly on the health of the trees going into the fire, and that “partially burned trees may be already stressed from years of drought.” But there are several other factors that influence whether or not a tree will survive a fire, including the health of the crown, damage to buds and twigs, and root damage.
Research has found that ponderosa pine trees with up to 90 percent of their top or crown scorched from fire may still survive. But when only a small portion of the crown escapes the fire and stays green, the tree will not produce as much energy for nourishment. That means the tree will have a harder time fighting off an attack from the bark beetle. Sometimes a tree will survive a fire, only to be killed later by bark beetles.
Trees that are orange with scorched needles are more flammable than trees that are green, but once the needles fall off, these trees are actually less likely to burn. Will they grow new needles? Some trees might, especially on their higher branches, but this depends on how badly the buds were damaged.
Yet another factor is the heath of the tree’s root system, which depends on the condition of the forest floor. In areas that haven’t burned in a long time there is a thick layer of leaf litter, or duff, that builds up. Sometimes, lots of tiny roots develop in this area, and then the roots are killed when the duff burns during a forest fire.
Some partially burned trees will survive, and some will not. It’s sad to watch an old, stately ponderosa pine become a fire’s victim. But tall trees that die open up areas for smaller trees to thrive. Dead trees don’t mean the end of a forest, although the forest may never in our lifetime look the way we remember it.