ALTADENA, Calif. — Following the Southern California wildfires, many survivors returned to find their homes destroyed, with little left standing on their property. Among the few things that often remained were trees.
Typically found with charred bark, these trees are being assessed by arborists to determine which ones can be saved during the U.S. Army Corps of Engineers wildfire debris removal program.
Victor Velazquez, a locally-based arborist with Tetra Tech described the evaluation process.
“We check the cambium, folium, and xylem and make sure the tree is still alive. If it’s alive, the tree will still be green underneath a small scraping of the charred bark. Dead trees are gray or black. We don’t go any deeper than necessary, so we only check the outer layer,” Velazquez said.
In addition to bark scrapings, arborists look for other indicators.
“If more than 50% of the tree is burned and no foliage is regrowing, that’s how you know the tree is completely dead. It’s now more than three months after the fires. Any trees that aren’t showing signs of life are totally gone. If you walk up to a tree and there are a few spots with leaves, but there’s more dead than alive, then it’s just showing signs of response growth. That tree is essentially using its last bits of stored energy but is dead,” Velazquez added.
For those with trees that can still be saved, they aren’t out of the woods yet.
“The scraping can injure the roots that were under the topsoil. Unfortunately, we are going back over trees that were first tagged as showing signs of life, but a month or more later, they aren’t alive. Now these trees pose a risk to the homeowner and others,” Velaquez said.
While arborists are employed by USACE across the United States, having local experts like Victor—who know the soil, trees and vegetation of the area — is crucial. Being able to tell homeowners what will and won’t grow back, and making the correct decisions, is key to clearing land so survivors of the wildfire can move forward with rebuilding.