Ken Bevis, DNR Stewardship Wildlife Biologist
Historically, dry eastern Washington forests saw frequent low intensity fires that reduced stocking levels and maintained stand structures dominated by large overstory trees. In many places the result was a mosaic of large trees, scattered and in clumps, with frequent openings and areas of grass and shrub species such as choke cherry, elderberry, willow, buck brush, etc. Native wildlife species adapted to, and thrived in these conditions. However, for the last 100 or so years, humans have aggressively controlled the fire regime, leading to overstocked stands, less resiliency to drought, insects, and fire, and a decrease in wildlife habitat.
Today, we use words like “Forest Health” and “Fire Wise” to describe thinning and other management actions designed to improve stand health. However, when the treatment is too aggressive it results in simplified habitats that lack the structure needed by many of our native wildlife species.
Can you have a healthy, fire wise forest and promote habitat diversity? You bet! With a little additional planning, mechanical thinning can be used to promote wildlife habitat, enhance individual tree vigor and decrease fuel buildup. When you or your contractor lay out the unit:
- Identify and mark important structural elements such as snags and downed logs for retention.
- Define specific areas for different types of treatment.
- Protect all of the large snags and logs.
- Keep larger trees as foundational units in an irregular pattern, averaging the desired spacing.
- Retain shrub (mid-canopy) habitat across the treated area to create and maintain a mixed habitat structure.
- Utilize “Fire Wise” techniques around all structures.
Useful techniques include:
- Targeting approximately 10% of the area in the unit for wildlife structures.
- Leaving patches uncut between ½ to 1 ½ dominant tree heights for wildlife cover.
- Locating and leaving particularly rich patches of native shrubs, emphasizing those that bear fruit like elderberry, chokecherry, and vine maple. If the shrubs are a little leggy, prune them or thin them minimally.
- Placing leave patches in strategic manner to provide some screening for larger animals such as deer, elk and bear in the back portions of the treated areas.
- Leaving the lower limbs on trees where the limbs aren’t associated with other ladder fuels.
- Avoiding existing large wood with the machinery.
- Aiming for two hard and two soft snags per acre. If they don’t exist, create them by cutting off the largest thinning trees (7” to 8” dbh) as high as the sawyer can reach. Remember – a tall stump is a short snag!
- Using larger pieces of wood as bottom layers for constructed habitat piles. Try for a density of 2 to 3 piles per acre and place them away from roads and major access points. Dispose of the majority of smaller material and stack smaller diameter logs into piles of 3 to 8 pieces to create a large log surrogate.
- Leaving a few patches of large leave trees with crowns within 3 feet of each other or touching to allow canopy wildlife species to travel easily between trees. This could be part of a leave clump or a small area in or adjacent to an opening.
Many species will benefit from these techniques including arboreal mammals (Douglas, red, western gray and flying squirrels), deer and elk, canopy dwelling neotropical migrants such as the western tanager, shrub loving songbirds (warblers, towhee), down log dependents such as fence lizards and chipmunks, and of course, woodpeckers and other cavity dwellers.
For more information, contact the DNR Stewardship Wildlife Biologist Ken Bevis at Ken.Bevis@dnr.wa.gov.