Last summer on July 7, 2014, my husband and I landed in Fairbanks, Alaska after a 10-day wilderness river trip. We turned on our cell phones and found text messages about a brush fire along Skyline Drive next to our home. Earlier that morning, our house-sitter loaded our car with dogs and musical instruments under a Level 3 evacuation order. Fortunately, skillful firefighters and a dozer driver plowed a fireline on the western flank that effectively stopped the flames along the top ridge of Saddle Rock City Park. We were lucky to have no winds that day.
For thousands of years, our east-side Cascades ecosystems have been subjected to naturally occurring wildfires. Plants provide the fuel for wildfires. Resident plants are suited for long-term survival in their environment, and many have adaptations to ensure persistence following wildfire.
Very little heat is transferred into the soil when a fast-moving, low-intensity wildfire moves through shrub-steppe ecosystems. Many long-lived perennial grasses, wildflowers, and some shrubs re-sprout after the fire. Big sagebrush (Artemesia tridentata) is mostly killed and will not re-sprout from roots, but instead will regenerate from windblown seeds or from seeds stored in the soil. Low intensity fires improve seed-sprouting conditions by reducing crowding. Fewer plants mean less completion for limited water and nutrients. Ash increases nutrient availability, fertilizing the soil.
Our collective human activities in the urban-wildland interfaces have increased the frequency of fire in shrub-steppe ecosystems. Before European settlement, individual patches of shrub-steppe burned on average, about every 75 years, as a result of lightning strikes. These fires were usually small in size, due to lack of fuel as patches of rocks and bare ground separated bunchgrasses and shrubs. With low levels of fuel, the fires burned relatively cool and little heat penetrated into the soil. Introduction of cheat grass since the late 1800s has created a fine, continuous layer of fuel connecting the bunchgrasses and shrubs, allowing fires to burn larger areas.
Today, shrub-steppe wildfires return more frequently, consumer greater acreage, often threaten structures, and bring negative consequences for plant regrowth. Newly burned ground allows invasive non-native weeds to establish and out-compete native plants. When a patch of shrub-steppe burns often, it can convert to a grassland, devoid of shrubs that must regrow from seed. Reduction of native plant diversity after fire results in loss of food, cover, and nesting areas for native animals, especially those that depend upon big sagebrush. Burned soils are vulnerable to wind and water erosion.
One year post-fire at Saddle Rock, visitors have to look closely to see evidence of the 2014 burn. This summer, other Wenatchee neighborhoods that abutted shrub-steppe hillsides were devastated by wind-blown flames. We all have a heightened new awareness of our collective need to learn about wildland fire and ways to decrease risks along the urban-wildland interface. This fall, the Wenatchee Valley Museum and Cultural Center will feature a wildfire exhibit and offer education programs to help us all begin to take actions to decrease our risks.
Enrollment is now open for Susan’s fall 12-week Wenatchee Naturalist course, offered by Wenatchee Valley College Continuing Education with either a daytime and evening option.