Blue Spruce Damage Indicates Elevated Risk of Douglas-fir Tussock Moth Outbreak

Douglas-fir tussock moth
Source: Forest Health Highlights in Washington, 2016, by DNR and U.S. Forest Service.

Recently I have begun to observe damage to ornamental blue spruce throughout the area of Colville, Washington. Upon closer inspection of these trees, I found that they are being defoliated by the Douglas-fir tussock moth. The Douglas-fir tussock moth is a native defoliator of Douglas-fir, true firs (such as grand fir) and spruce. For reasons unknown, a year or two prior to an outbreak of Douglas-fir tussock moth on forested land, we tend to see defoliation of ornamental trees such as blue spruce. Given the number and area of defoliated blue spruce I have been seeing, it is likely we will have an outbreak of the Douglas-fir tussock moth sometime within the next two years. Unfortunately, no relationship has been found between the location of the sentinel trees and the forested areas that will be defoliated in the future. In other words, we know that there will likely be an outbreak, but we do not know exactly where it will occur.

Outbreaks of Douglas-fir tussock moth are cyclical, typically occurring every 7 to 14 years. On average, outbreaks last 2 to 4 years. The last outbreak began in 2008 (Figure 1); therefore, we are due for another.

 

Lifecycle of the Douglas-fir tussock moth

The Douglas-fir tussock moth spends the winter months in the egg stage. Eggs are protected in gray, hairy masses that are approximately an inch in size. An egg mass can contain as many as 350 eggs. The eggs will hatch in late May or early June, depending upon temperatures.

The caterpillar (larvae) will be present from June through August. The caterpillars are quite hairy, with two long hairy tufts projecting from the head and the rear end. They also have four dense tufts of hair on their back, called tussocks, which are whitish in coloration with red tips.

The caterpillars pupate in July-August. Cocoons are grayish-brown, about one inch in size, and can be found on the foliage and trunk of trees as well as in the understory.

The pupae develop into moths and begin emerging in late July. They will continue to be active through November. The females are gray-brown, with large abdomens and are wingless. The males have gray-brown forewings and reddish-brown hind wings. They also have large, feathery antennae.

 

Damage: What to look for

The larvae feed on new needles in the upper crown first. These needles will turn an orangish-brown color (Figure 2). Overtime, the caterpillars will disperse to the lower crown and begin defoliating needles there. The larvae will feed on both new and old needles, sometimes completely defoliating the tree.

trees defoliated by the Douglas-fir tussock moth
Figure 2. Left: Ornamental blue spruce defoliated by the Douglas-fir tussock moth. Center: Ornamental blue spruce and white fir defoliated by the Douglas-fir tussock moth. Right: Close-up of blue spruce defoliation by the Douglas-fir tussock moth. Photos: Melissa Fischer/DNR.

In addition to defoliation, you may find the moth in one of its life stages, depending upon the time of year. Another thing to look for is silk and/or frass ( poop) on the branches (Figure 3).

Signs of Douglas-fir tussock moth
Figure 3. Left: Douglas-fir tussock moth caterpillars feeding on blue spruce foliage. Right: Silk and frass (poop) produced by the Douglas-fir tussock moth. Photos: Melissa Fischer/DNR.

Management

Defoliation by the Douglas-fir tussock moth can cause top and branch kill, which can lead to reduced vigor and growth loss. This can increase susceptibility to bark beetle attack or infection by diseases. Complete defoliation or several years in a row of defoliation can lead to mortality.

Douglas-fir tussock moth is usually controlled over time by natural enemies such as predators, parasites, viruses, cold temperatures, and/ or starvation (eating themselves out of house and home), but can also be managed through use of insecticide treatments.

Bacillus thuringiensis var. kurstaki (Bt) is an insecticide that is specific to Lepidoptera larvae. Its specificity is advantageous because it does not affect other insects, such as the natural enemies that help reduce populations. Because Bt is specific to the larval stage, it would have to be applied when the Douglas-fir tussock moth is in the caterpillar stage.

In forested settings, severe damage can be prevented through thinning. It would be best to remove host trees (Douglas-fir, grand fir, Engelmann spruce) and favor the retention of non-host trees (ponderosa pine, western larch, lodgepole pine) thereby reducing the amount of food available. Additionally, thinning breaks the crown continuity within a stand, so that when the caterpillars disperse, many will fall to the ground and dessicate or be eaten by passing birds.

If you think you may have a sentinel tree on your property, I would love to know about it! Feel free to contact me via Melissa.Fischer@dnr.wa.gov.

By Melissa Fischer, forest health specialist, Washington State Department of Natural Resources, Northeast Region, melissa.fischer@dnr.wa.gov 

Potential for Douglas-fir Beetle Outbreaks in Eastern Washington

Douglas fir killed by bark beetle
Beetle damage in stand of Douglas fir. Photo: Kenneth E. Gibson, USDA Forest Service, Bugwood.org

Several windthrow events in 2015 have paved the way for a potential outbreak of Douglas-fir beetle in areas of eastern Washington this spring (2017).

Douglas-fir beetle egg and larval tunnels
Characteristic pattern of Douglas-fir beetle egg and larval tunnels. Photo courtesy of Oregon Department of Forestry.

The Douglas-fir beetle is a bark beetle that normally breeds in felled, injured, windthrown or root-diseased Douglas-fir. It may also attack western larch, but can only produce brood in downed trees. At outbreak levels, this bark beetle can attack and kill large diameter, healthy Douglas-fir. Outbreaks tend to occur after extensive windthrow events such as was seen in 2015. Outbreaks may also occur after defoliation events, fire and extended drought. Dense stands surrounding areas where windthrow, defoliation, fire and drought events have occurred may be at high risk for an outbreak, particularly if those stands contain a 50 percent or more component of Douglas-fir that are greater than 120 years of age and larger than 14 inches DBH (DBH = diameter at breast height; diameter of a tree bole 4.5 feet from the base).

The Douglas-fir beetle has one generation a year. Brood that developed through 2016 will pupate and emerge as adults this spring. Once emerged, they will begin attacking standing trees surrounding the windthrow, as the windthow is no longer habitable for them.

What can be done?

The best approach to prevent an outbreak this spring is to salvage any large diameter Douglas-fir or western larch that were downed by the storms prior to the adult beetle flight, which should occur in April, depending on temperatures. Windthrown trees can also be burned or chipped on site if salvage is not an option. Time is running out; if you find you cannot take care of this material, the use of the anti-aggregate pheromone MCH is another option.

A pheromone is a chemical released by bark beetles that is used to affect the behavior of other beetles of the same species. Aggregating pheromones attract beetles, while anti-aggregates repel them. A bark beetle might use an anti-aggregate to prevent overcrowding within a tree. An anti-aggregate basically tells other beetles that there is no room for additional inhabitants in the tree.

MCH bubble capsule stapled to a tree
MCH bubble capsule stapled to a tree. Photo: US Forest Service.

The Douglas fir-beetle naturally produces an anti-aggregate to repel others. A synthetic version of this anti-aggregate, MCH, has been produced and is available for purchase through several online companies. MCH comes in a “bubble capsule” and can be used to protect individual live, high-value Douglas-fir or even an entire stand. For individual tree protection, two bubble capsules can be stapled on either side of a Douglas-fir bole at approximately 6-8 feet from the ground for a tree less than 24 inches DBH. Four bubble capsules should be used for Douglas-fir larger than 24 inches DBH. To protect a stand of Douglas-fir, 30 bubble caps per acre can be evenly placed through the stand.

MCH costs approximately $2.50 per capsule and should be hung prior to the beetle flight in April. It is advisable to contact your local forest health specialist if you are considering this method of management. Additional information about this method can be found in the free publication, “Using MCH to protect trees and stands from Douglas-fir beetle infestation,” published by the US Forest Service.

By Melissa Joy Fischer, forest health specialist, Washington State Department of Natural Resources, melissa.fischer@dnr.wa.gov

 

I Hear Bugs Chewing the Wood Inside my Trees!

ugphotos1-3
TOP: Figure 1. Example of a longhorned beetle: spotted pine sawyer (Monochamus clamator) Photo: Richard C. Hoyer, Bugguide.net MIDDLE: Example of a metallic wood borer: Golden Buprestid (Buprestis aurulenta) Photo: Melissa Fischer/DNR BOTTOM: Figure 3. Example of a woodwasp: Sirex nigricornis Photo: Schiff et al. 2006

I hear bugs chewing the wood inside my trees!

Many land managers have contacted me in a panic saying that they could hear bark beetles feeding in their trees. Although bark beetles may be present in those trees what they were likely hearing is wood borer activity. Wood borers tend to be much larger than bark beetles and are, therefore, more likely to be heard chewing away inside trees.

While bark beetles feed solely on a tree’s phloem, wood borers feed on sapwood and heartwood as well as phloem. Native wood borers attack stressed, dying, or dead trees; there are very few native species that actually kill trees.

Wood borers are attracted to volatile gases released by dead or dying trees and lay their eggs under the bark of these trees. Once the larvae hatch, they begin feeding on the inner bark and then tunnel into the wood. The larvae are white, legless grubs and can be quite large. They are valued as a food source by woodpeckers (they make great fishing bait too!) and woodpecker activity is often seen on trees that contain wood borers. The tunnels produced by larval feeding activity have a random pattern and increase in size as the larvae grow.

Frass (beetle poop) is likely to be present within the tunnels. Unlike bark beetle frass, which is fine and reddish in coloration, wood borer frass tends to look more like shredded wheat and is white in color. When wood borers develop into adults, they emerge from trees and leave exit holes that are typically quite a bit larger than those left by bark beetles.

Wood borers play an important ecological role by introducing wood decaying organisms into dead and dying trees which, in turn, helps to speed nutrient cycling. Typically, no management is necessary for native wood borers in a forested setting. Wood borers can damage lumber, but damage is unlikely to occur if the wood has been treated.

Types of Wood Borers

bugphotos4-6
TOP: Figure 4. Asian longhorned beetle Photo: Joe Boggs, Bugwood.org MIDDLE: Figure 5. Citrus longhorned beetle Photo: Art Wagner/Forestry Images. BOTTOM: Figure 6. Emerald ash borer. Photo: Marianne Prue/Bugwood.org

There are three common wood borer families; Cerambycidae, Buprestidae, and Siricidae. The family Cerambycidae, often called longhorned beetles (adults) or roundheaded wood borers (larvae), includes many species. Adults can range in size from ¼ to 2 ½ inches in length. Adults, particularly the males, have long antennae, hence the name longhorned beetle (Figure 1).

The family Buprestidae are commonly known as metallic (adults) or flatheaded (larvae) wood borers. Similar to longhorned beetles, there are many species, and adults may be ¼ to 2 ½ inches in length. Metallic wood borers have small antennae and some are very beautiful, with iridescent or metallic coloration somewhere on the body (Figure 2).

Flatheaded woodborer larvae can be differentiated from roundheaded wood borer larvae in they have a flattened and broadened area beneath the head (thorax) that gives the appearance of a flat head. Rather than the round exit holes left by roundheaded wood borers, flatheaded wood borers leave D-shaped exit holes.

The family Siricidae, often called woodwasps or horntails, are in the order Hymenoptera (i.e., wasps), unlike Cerambycidae and Buprestidae which are in the order Coleoptera (i.e., beetles). Adults may be ½ to 1 ½ inches in length and have a short hornlike process at the end of their bodies. Females have an additional stinger-like ovipositor which is used to oviposit eggs under the bark of trees (Figure 3).

Woodwasp adults can be distinguished from common wasps in that they have thick waists and neither males nor females can actually sting. Woodwasp larvae look similar to roundheaded wood borers but have a small spine at the end of the body. Woodwasps are particularly attracted to fire damaged trees and all except one western species feeds on conifers.

Although native wood borers typically attack stressed, dying and dead trees, several invasive species have been introduced into the United States that are incredibly damaging. The Asian longhorned borer (Anoplophora glabripennis) was introduced into the eastern United States in the early 1990’s. The Asian longhorned beetle feeds on many deciduous species (birch, horse chestnut, poplar, willow, elm and ash), but maples are one of its favorites.

This species has killed thousands of trees in New York and Chicago. Adults are large, 1 to 1 ½ inches long, and have wings that are shining black with irregular splotches of white. The antennae have bands of black and gray and the feet and legs have slate-blue “hairs” (Figure 4). This species can be confused with another invasive, the citrus longhorned beetle (Anoplophora chinensis, Figure 5).

bugphotos7-8
TOP: Figure 7. The native Prasinalia cuneata. Photo: William Ericson, Bugguide.net. BOTTOM: Figure 8. Sirex woodwasp (Sirex noctilio) female on the left and male on the right. Photo: http://www.sciencephoto.com

The emerald ash borer (Agrilus planipennis) is an invasive metallic-green wood borer (Figure 6) currently found in 30 states. The emerald ash borer attacks ash trees and has killed hundreds of millions of ash in North America. If you have seen rectangular purple traps hanging in trees alongside the road, these traps are being used to monitor for the emerald ash borer, which is attracted to this particular color. The emerald ash borer may be confused with many native metallic wood borer species, such as Prasinalia cuneata (Figure 7).

The European woodwasp (Sirex noctilio, Figure 8) has been accidently introduced into the eastern U.S. as well. This species attacks and kills living pines. Similar to the emerald ash borer, this species may be easily confused with native species.

Reports from citizens help scientists track the spread of these pests. To report a potential invasive species in Washington state, take a picture if possible, and contact the Washington Invasive Species Council.

By Melissa Fischer, DNR landowner assistance/stewardship forester, melissa.fischer@dnr.wa.gov 

References:

Fall is Tree Thinning Time for Forest Landowners

Ponderosa pine stand thinned and pruned
Ponderosa pine stand thinned and pruned to prevent spread of low-intensity ground-level fires into the crowns. Photo: US Forest Service.

Fall is just around the corner and for those who own forested land, if you have not already done so, you may want to consider thinning some trees out. People who own forested property are often hesitant to remove trees for various reasons. Why should you thin? What are the advantages?

Forest health

Many people think of a forest as a stand of trees existing together in harmony. In reality, a forest, particularly a young forest, contains trees competing with one another for their life-sustaining resources: sunlight, water, and nutrients.

There’s even a priority list of sorts within individual trees. It varies depending on the species but, in general, the order in which resources are allocated is, from highest priority to lowest priority:

  1. Maintenance of respiration
  2. Production of fine roots
  3. Reproduction
  4. Height growth
  5. Diameter growth
  6. Insect and disease resistance mechanisms, and
  7. Storage

A dense stand of tall, thin lodgepole pine, is a good example of a stand where there are enough available resources to allocate up to priority number 4, height growth, but not enough resources to allocate much to priority number 5, diameter growth, or beyond. This lack of resources will affect overall forest health, as the trees will not be able to allocate resources to insect and disease resistance mechanisms.

What sort of insect and disease resistance mechanisms do trees have? Let’s use bark beetles as an example, since certain species of bark beetles can cause extensive tree mortality.

In most coniferous species a resin duct system produces oleoresin when the tree is wounded, such as a broken branch. Oleoresin is basically a mixture of essential oil (turpentine) and nonvolatile solids (rosin). Oleoresin is considered the primary defense of conifers against bark beetle attack. Beetles that attempt to attack a conifer that is in good health and capable of producing adequate, pressurized oleoresin are typically immobilized in the resin or killed by drowning in it. The chemical makeup of the oleoresin is important as well, as some of the volatiles released from the oleoresin are toxic to bark beetles.

Dense stands, which tend to grow slowly, are consistently associated with bark beetle infestations. The susceptibility of a stand to bark beetle infestations may be changed by reducing competition between trees; in other words, thinning. In western North America, thinning has long been advocated as a preventative measure to reduce or alleviate the amount of bark beetle caused tree mortality. Thinning improves tree vigor and growth. It also decreases the likelihood of bark beetle attacks on individual trees by allowing the site’s available resources to be concentrated on fewer stems, which means trees will have enough resources to allocate to priority number 6 (insect and disease resistance mechanisms).

Wildfire risk reduction

Successful fire exclusion over the past 60 to 70 years has resulted in greater stand densities and a change in species composition. In that span of time, many forests in dry ecosystems, such as eastern Washington, have transitioned from fire-adapted, open ponderosa pine stands to dense pine and Douglas-fir stands. In moist forests, the change has been from open stands of western white pine and western larch to relatively short, closed stands of grand fir, western hemlock and western redcedar. These changes have led to an increase in the occurrence of crown fires (fire that spreads from treetop to treetop), the most intense type of wildfire, and often the most difficult to contain.

Thin from below
Example of thin from below. Photo A: Before thinning. Photo B: After thinning. Photos: Michelle Ensminger.

 

Ponderosa pine, western white pine and western larch all tend to be tall and self-prune (the natural removal of lower limbs that don’t receive enough sunlight to survive). Western white pine and western larch have lower volume crowns and carry their crowns well above surface fuels compared to true firs, Douglas-fir, western hemlock, and western redcedar. Because of these attributes, western white pine and western larch do not carry crown fires well and tend not to create ladder fuels (fuels in the lower canopy that carry fire up into the crowns of trees). In contrast, stands dominated by true firs, Douglas-fir, western hemlock, and/ or western redcedar do not self-prune well. They tend to carry large branches low in the canopy and have relatively voluminous crowns. Stands dominated by these species usually support crown fires.

Thinning cannot alter all variables that influence fire behavior, but it can influence factors such as species composition, available fuel, fuel arrangement, fuel moisture and surface winds. The objective of thinning in wildfire risk reduction is usually to prevent or slow the spread of crown fire by reducing surface and ladder fuels. Thinning also raises the height of overstory crowns and breaks up the connectedness of crowns, which reduces tree-to-tree spread of crown fires.

Wildlife management

Species associated with fairly open canopies and an open forest floor may benefit from thinning treatments. Thinning a stand of trees increases the amount of sunlight reaching the understory, which stimulates the growth of grasses, wildflowers and native shrubs. Elk, deer, and moose will likely benefit from the increase in forage quantity and quality. Small mammals such as chipmunks and deer mice may increase in number, particularly after thinning in Douglas-fir and ponderosa pine forests. This may be advantageous to species of hawks, owls and eagles that prey on small mammals in open forests and small clearings. Although not often considered as part of the wildlife community, pollinators such as moths and butterflies may also benefit from changes in structural diversity as a result of fuel reduction treatments that increase the amount of light reaching foliage and the forest floor.

Timber production

If you are managing your forested land for future timber production, thinning will be an important part of your management plan. Thinning releases resources to the residual trees allowing them to allocate to their fifth priority, diameter growth, which leads to an increase in tree volume. This increase in diameter growth results in an increase in overall stand value.

Thinning techniques

The tools and methods by which thinning is implemented are quite varied, and can result in significantly different stand structures. The type of thinning you select may depend on your objectives and on individual stand characteristics, such as species composition.

When managing for forest health and fuel reduction, private landowners typically use the “thin from below” method. Thinning from below consists of removing trees from the lower canopy, leaving larger trees to occupy the site. This method mimics mortality caused by competition or surface fires and concentrates available resources on larger, healthier, fire-adapted trees, while removing the stagnant, unhealthy trees.

Thinning is best accomplished in the late summer and early fall if possible. At this time trees will be least susceptible to damage from the thinning operation and the populations of insects that may be attracted to the slash created will be low. Winter also is an acceptable time to thin, but can lead to soil compaction and erosion if done at the wrong time. Thinning in spring and summer is not recommended as it can attract insects such as bark beetles and can affect wildlife, particularly nestlings.

For more information about thinning your property, please visit the Forest Stewardship Program and the Landowner Assistance Center pages on the Washington State Department of Natural Resources website.

By Melissa Fischer, Forest Health Specialist, DNR Northeast Region, Washington State Department of Natural Resources

 

Resources to  learn more:

Fettig, C.J., Klepzig, K.D., Billings, R.F., Munson, A.S., Nebeker, T.E., Negron, J.F., and Nowak, J.T. 2007. The effectiveness of vegetation management practices for prevention and control of bark beetle infestations in coniferous forests of the western and southern United States. Forest Ecology and Management. 238: 24-53.

Graham, R.T., Harvey, A.E., Jain, T.B. and Tonn, J.R. 1999. The effects of thinning and similar stand treatments on fire behavior in western forests. U.S. Forest Service, Pacific Northwest Research Station. PNW-GTR-463.

Pilliod, D.S., Bull, E.L., Hayes, J.L. and Wales, B.C. 2006. Wildlife and invertebrate response to fuel reduction treatments in dry coniferous forests of the western United States: A synthesis. U.S. Forest Service, Rocky Mountain Research Station. RMRS-GTR-173.

Fuels Reduction and Improved Habitat: Try SLLOPPS (Snags, Logs, Legacy, Openings, Patches, Piles and Shrubs)

Overly aggressive thinning near Lake Chelan
This natural-looking setting near Lake Chelan is anything but natural. Overly aggressive thinning has left it without the snags, down logs, open patches and other features that wildlife need for habitat. Photo: Ken Bevis/DNR

Thinning and fuels reduction are necessary treatments in today’s overstocked dry forests. But sometimes, aggressive implementation of prescriptions can degrade habitats beyond what is really needed for fuels treatments. This article will make a few suggestions on ways to balance these objectives.

If you live in a dry-but-forested area, such as eastern Washington, and are planning a thinning or harvest on your forestland, here’s a simple habitat acronym for you and any contractors you hire to keep in mind: SLLOPPS, which stands for snags, logs, legacy, openings, patches, piles and shrubs. Incorporating these seven features into your project will help reduce future risks of wildfire and insect infestation while promoting a healthy natural habitat for beneficial wildlife.

Natural Forests

In its natural state, the dry forest ecosystem experiences frequent low-intensity fires. This cycle of periodic fire results in tree stands dominated by large, old trees and, generally, not over-stocked with smaller trees and other growth as many stands are today.

Historic photos of eastern Washington and Oregon show classic stands of old ponderosa pine (and some Douglas-fir) with riders on horses and wagons cruising through the open, grassy understory. These conditions did not occur everywhere, but the prevalence of ground fire at 7- to 15-year intervals ensured that these stands seldom suffered crown fires. Individual tree vigor was strong thanks to reduced competition for resources. Thus, fire disturbance helped maintain these forests.

These stands contained large standing dead trees as well, and some enormous down logs that could survive low intensity fires. Regeneration was often patchy, resulting in numerous openings and areas of dense regeneration that might flash out in the next fire. Many shrub species are fire adapted, and after burning would either re-sprout in clumps, or sprout from seed in the soil, creating a vigorous shrub understory.

Wildlife species, such as white headed woodpeckers and flammulated owls, are adapted to this open forest and its plentiful snag and log habitats and rich understory of shrubs.

Human Actions

Native Americans are believed to have played a significant role in the fire ecology of the inland Northwest. Their activities led to the landscape-shaping fires that produced the stands encountered by the early European settlers to this region. Also during this time, lightning fires often would burn until season-ending weather events such as snowfall.

Logging (until very recently) in these dry forests usually removed the large, excellent quality trees. This was economically advantageous but ecologically unfortunate, as these trees would have been the survivors of the fires. Without recognizing what we were doing, we removed the backbone of the dry forest habitat.

The biology of dry forest tree species involves producing large numbers of seeds to give a chance for a few to survive the inevitable fires. Fire suppression efforts that began in the early 20th century inevitably led to the dense stands that we see on the landscape today.

Now, we are aggressively thinning across the landscape, where funding, motivation and political will let us. Unfortunately for wildlife, caution over “fire safe” and “forest health” can lead us to produce stands that are simply “too clean” and “parked out” to serve as quality wildlife habitats.

In this article, I will discuss seven tools — snags, logs, legacy, openings, patches, piles and shrubs (SLLOPPS) — that can provide some habitat diversity while addressing the issues associated with overstocked stands and tree mortality due to stress and insects.

Prescription for Habitat Diversity

SNAGS: Some of the most important habitat features in any forest are made of dead wood; specifically, standing dead trees (snags) and down logs. Live trees with dead portions of their stems and branches can also fill this role. Insects reside in the dead wood, often feeding on fungi, while woodpeckers, nuthatches, chickadees and other birds feed on these insects. Cavities created by woodpeckers during regular nesting and courtship behavior can provide homes for secondary cavity species such as bluebirds or flying squirrels. Because many of these species are voracious feeders on insects, including some that are forest pests, their presence helps to keep the forest healthy but only if suitable habitat is provided so that they can occupy territories for feeding and nesting.

recently thinned stand with several wildlife features
This recently thinned stand on private land displays the key elements (snags, down wood, piled chipped materials, etc.) that make it useful wildlife habitat. Photo: Ken Bevis/DNR

DNR’s cost share thinning projects target dangerous fuels which are generally woody stems less than 3 inches in diameter. These smaller stems will carry fire quickly and spread flames into crowns. Larger wood, which ignites more slowly and creates less flash hazard, can be left for habitat and soil enrichment.

Snags should be greater than 10 inches in diameter at breast height (dbh) in order to provide opportunities for large excavators, such as the hairy woodpecker or flicker, to create cavities. Natural snag densities vary tremendously, so the best policy for habitat is to maintain all snags greater than 10 inches dbh, and protect them from firewood and timber harvests. Forest practices laws in Washington state require 2 wildlife trees per acre; although this is likely not a biologically optimum number, it can serve as a target for forest management. Following this rule could include creating 2 snags per acre where they do not exist. Optimum snag densities are closer to between 12 and 16 snags per acre but in managed forests this is a hard number to reach.

LEGACY: Big trees are the backbones of dry forest ecology. Keep large trees, including defective ones. They will produce more cones and branch surface area than younger stems, provide perches and nest sites, and will become future dead wood.

LOGS: Logs can be treated the same as trees by emphasizing the protection for all large pieces by preventing them from being piled or burned, and by leaving them in place. Scattering tops and large pieces of unmerchantable wood across treated units are additional desirable actions to improve habitat.

OPENINGS: Wildlife also benefits from openings—areas within the forest where all, or nearly all, of the overstory trees are not present. These openings allow shrubs and grasses to flourish as wildlife forage. Natural meadows are the best candidates for these areas, but openings also can be embedded within stands to allow big game animals to feel secure and to provide habitat for other wildlife associated with edge habitats.

PATCHES: Denser habitats made up of young conifers and shrubs provide quality habitat for many species, such as feeding or nesting songbirds, and as browse and cover for big game. Retaining small patches of trees in thinning units can provide this habitat, but it requires forethought and follow through. Before thinning, mark areas from 30 to 50 feet in depth, and at least the same distance in length, or preferably longer. These areas should be left unthinned, (or thinned lightly), in order to maintain shrubs, trees and other mid-level vegetation while providing cover for large mammals such as deer, elk and bear. These patches should be configured across forest units so as to break long-sight distances, and staggered at distances of 200-300 feet apart.

PILES: Wood piles can be left as distinct habitat elements and act as surrogates for down wood. They will provide cover for many species of wildlife. The best approach to creating piles for wildlife involve placing at least three to five layers of larger logs that are crisscrossed, or laid lengthwise in triangular arrangements. When covered with a few layers (about 2 to 3 feet deep) of fine branches, the pile will provide habitat with small interior spaces. Habitat piles also can be used as a non-burning solution for managing slash. Place piles constructed for wildlife away from overhanging trees so that if a pile should catch fire it will not act as a ladder fuel to the crowns. It’s best to provide these wildlife piles at a rate of two to three per acre, preferably in clusters away from roads, trees and structures. Because these piles are not intended as sources of firewood they should be marked for retention after the thinning work is done but before other brush or slash piles are burned.

SHRUBS: Many shrub species provide excellent fruit and vegetation for many types of wildlife. Ask your local U.S. Conservation District office which shrubs are the best for your area. Elderberry is always a good choice, as is most anything else with “berry” in the name.

Putting it All Together

A general rule of thumb for 10 to 15 percent of the project area to be made up of one, or all, of these desirable wildlife habitat elements. Providing patches of habitat for cover, or around a feature such as a snag, can provide much in the way of habitat diversity and reduce the potential impact of thinning projects on the diversity of animal and plant species that live in your forest.

If done thoughtfully, thinning projects that maintain snags, logs and shrubs a sufficient distance from overstory trees will provide quality habitat while improving the health and resilience of dry forest stands. Work closely with contractors and be very specific as to where these habitats are to be provided. Thinning will increase resilience to both fire and insects through improved individual tree vigor, which in turn benefits many wildlife species. Risk of catastrophic loss of entire stands can be avoided with good projects too. And that benefits wildlife in the long term.

Case Study: Swauk Pines, Kittitas County

In 2015, Suzanne Wade of the Kittitas County Conservation District (KCCD) partnered with private landowners at Swauk Pines, a new 50-acre development near Cle Elum made up of 3- to 8-acre parcels in a dry pine forest. The Taylor Bridge fire (2012) came very close to this area and created significant motivation for landowners, some of whom had already built residences while others were in the planning stages, to reduce their wildfire risks while maintaining wildlife habitat.

Swauk Pines development before forest-thinning
BEFORE: Swauk Pines development near Cl Elum before forest-thinning treatments. Note the many small (less than 8” diameter) trees, trees with low branches and the heavy woody understory–all prone to spreading fire. Photo: Ken Bevis/DNR.

Most of the development was treated in a cost share project in which the KCCD worked closely with the thinning contractor to incorporate SLLOPPS principles into the forest treatments. These treatments included retaining large snags and logs, and including shrub patches. A bird survey was conducted before the project began to identify where to create open patches attractive to nesting birds.

Results

As a result of the strategic approach to forest thinning, habitat quality was maintained, fire risk was reduced, and forest health improved large. Homeowners were asked to take responsibility for the areas immediately around their houses. This project is an excellent example of successfully implementing multiple objectives.

Swauk Pines after thinning
AFTER: Swauk Pines after thinning to remove brushy overgrowth and most of the trees less than 8 inches in diameter. Note the retention of snags and patches of shrubs for wildlife. Photos: Ken Bevis/DNR

Including these habitat elements in thinning projects is only the beginning. Vegetation always grows back so the job of maintaining the levels of fuels acceptable to individual landowners is an ongoing task that will need to be revisited every few years.

Thinning and fuel reduction projects are crucial to help our forests survive the current rounds of drought and devastating wildfire. Including habitat elements in these projects is not only possible but an additional benefit of meeting our fire and forest health objectives.

For more information or to schedule a site visit to your forest property, please contact the DNR Small Forest Landowner Office. For information or assistance with habitat, contact DNR Landowner Assistance Wildlife Biologist, Ken Bevis at Ken.Bevis@DNR.wa.gov

By Ken Bevis, DNR Landowner Assistance Wildlife Biologist, Ken.Bevis@DNR.wa.gov