Scientists optimistic about recovery but on guard for weeds and erosion
By Marcy Stamper and Laurelle Walsh
Only two weeks after fire burned hundreds of square miles in this area, scientists have found 18-inch sprouts of Western sumac at Alta Lake and grasses and elderberry bushes emerging near melted irrigation lines along Beaver Creek.
At a scorched property on Finley Canyon, tender sprouts of lupine and yarrow punctuate the expanse of blackened soil, and even trees that appear fatally charred exhibit new growth.
Many of the ecosystems that burned in the Carlton Complex Fire are well adapted to wildfires, said Peter Morrison, executive director and senior staff scientist at the Pacific Biodiversity Institute (PBI), who mapped the burned area and has been studying regrowth after this and other fires.
The majority of vegetation types within the Carlton Complex perimeter were in the shrub-steppe habitat, where grasses and sagebrush burned, said Morrison. In fact, only 25 percent of the area that burned was forested. A small percentage was agricultural.
While extremely hot, dry and windy conditions stoked what firefighters described as unprecedented fire behavior, the fact that so much shrub-steppe burned also explains why the fire exploded so rapidly.
“Fire burns quickly through [the shrub-steppe] and oftentimes doesn’t do any damage underground,” said Morrison.
In the spring, native plants put a lot of energy into their roots and the underground biomass, even though above-ground parts begin to dry out and later become highly flammable, said Morrison.
“Our native habitats are adapted to fire and will recover quickly in most circumstances without intervention,” according to the Methow Conservancy, which is educating people about post-fire restoration and offering site visits to properties that burned.
“Fire is a natural process, as natural as the rain falling or the wind blowing,” said Morrison.
While fire is a natural process, many remnants of fire suppression are not. Fire lines, scraped down to mineral soil, leave scars that are highly susceptible to invasion by non-native species and noxious weeds, which establish themselves before slower-growing native plants do, according to the Conservancy.
The fire lines, like burned slopes with little or no vegetation, are also prone to erosion. Recent rains have already caused mudslides in the burned areas, several serious enough to close roads or damage fences rebuilt after the fire.
Fire lines created by firefighters are generally restored by the fire crews, who fill them in with displaced soil and plant material as the final stage of their work. Crews will also scatter slash and create diagonal water bars to prevent rains from carving deep gullies. People who created their own fire lines should re-seed and follow similar steps to prevent erosion.
The interagency team that coordinated the firefighting has a team of hydrologists, soil scientists, foresters and engineers assessing the condition of burned areas and probability of erosion. The Burned Area Emergency Response report will identify immediate and emergency actions to prevent erosion and flooding and recommend stabilization treatments.
Even rehabilitated fire lines remain more susceptible to weeds and need to be carefully monitored over the next several years, said the Conservancy.
The speed and success of recovery depends on what burned. Ponderosa pine and Douglas fir forests, while adapted to periodic fires—although much cooler ones than this summer’s blaze—are slower to regenerate than grasses and shrubs, said the Conservancy. And while burned trees provide wildlife habitat, they can also attract insects that threaten healthy trees.
While even trees that lost considerable foliage or needles are likely to recover, conifers that lost all their needles will not. If buds are intact—if they are bright green, not brown, when you slice into them—the tree will generally survive, according to the Okanogan Conservation District. Many trees will survive this season but will die in the next year or two.
The Conservation District recommends saving trees that are only 20 to 30 percent scorched. Of particular importance is the amount of scorch to the crown of the tree—it should be less than 50 percent for a good chance of survival, according to Karen Ripley, forest health program manager with Washington Department of Natural Resources (DNR). High-intensity crown fires generally kill trees.
DNR is also helping property owners evaluate the condition of their trees and the potential for salvage logging.
Many scientists believe that forest-management practices prevalent in the first half of the 20th century have contributed to dense forests with weakened trees that are more susceptible to serious fires.
After intense fires in the Northwest a century ago that burned 5 million acres and killed almost 100 people, the U.S. Forest Service began a policy of strict fire protection, according to an agency history. In 1935, the Forest Service enacted a policy to contain and control a fire by 10 a.m. or, if unsuccessful, by 10 a.m. the following day. Today the Forest Service recognizes fire as an important component of healthy ecosystems and policy has evolved accordingly, using suppression and prescribed fires.
PBI scientists were encouraged by their findings in studies of natural fire recovery after regional fires over the past two decades. Two months after the Thirtymile Fire, PBI found cottonwoods and aspens already 3 to 6 feet tall, despite complete mortality of above-ground trees.
Morrison believes that many of the areas that burned this summer will experience a significant long-term benefit in terms of ecosystem health. Vegetation such as fireweed, lupine, balsamroot and lomatiums tend to make big, showy displays in the first five years after a fire, he said. Sagebrush and bitterbrush that have not burned too severely will resprout from root crowns, but these species take longer to recover.
“My examination of recovery after numerous wildfires gives me confidence that our fire-dependent and fire-adapted ecosystems will recover well,” said Morrison.