The canopy layer in the forest—the interacting tree crowns that create a remarkable maze of three-dimensional spaces between and on the branches—is a habitat niche with specialized functions for many species of wildlife. The surfaces of these branches and leaves provide shelter and food for a wide variety of arboreal (forest canopy inhabiting) mammals, birds and insects.
Truly arboreal mammals are not as numerous as bird species, but are important members of the forest wildlife ecosystem. Our native conifer squirrels are the Douglas and red squirrels (members of the genus Tamiasciurus), locally known as chickarees. These two species are actually very similar, but occupy different habitat regions. Douglas squirrels are associated with wetter, westside type forests dominated by Douglas fir and hemlock. Red squirrels live on the drier and colder east side, as well as in Rocky Mountain forest types we have in Northeast Washington. Both are common and important mammal species directly tied to the forest canopy as conifer specialists, actively harvesting and caching cones each year. Who among us woods walkers hasn’t been scolded by one of these little dervishes?
Fungi (mushrooms), which help trees grow by adding root absorptive surface to trees, is food for squirrels. The squirrels spread spores throughout the forest through their feces. Flying squirrels occupy a similar niche, but work the night shift, often foraging on the ground for mushrooms to cache. For this reason, flying, Douglas and red squirrels can be considered keystone species in forest ecosystems, e.g., species whose presence has far-reaching impacts. These squirrels need canopy to provide hiding places and food, but also need down logs for cache sites, and woody cavities in snags for denning. Habitat for these squirrels also includes low branches for resting and eating cones dropped to the ground.
Caring for the Canopy
In our forestry activities, we often thin and manipulate stands in order to grow trees as quickly as possible. This can provide much benefit for wildlife using canopy as the trees mature, but we often will harvest them just as the cone production and canopy reach good habitat status. Pruning can help reduce fire danger, but also remove habitat used by these animals. Retain some full crowned, seed bearing trees through this, and the next rotations. Keep some dense patches in your stand. Don’t prune every tree and keep some low branches for wildlife. Diversity is the key to good habitat.
We can maintain and create diverse canopy while managing our forest stands for diverse structure and multiple objectives through thoughtful management and structural retention.
If you own a small forest woodland, advice and resources to keep your forest and its canopy healthy are as close the nearest DNR stewardship forester or WSU extension forester. Call one of us to arrange a site visit or to get additional information on how to provide wildlife habitat while managing your forestland.
This article was written by Ken Bevis, a DNR Stewardship biologist. It originally published in Forest Stewardship Notes, a quarterly e-newsletter produced by DNR and Washington State University Extension.
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Ken Bevis, DNR Stewardship Biologist
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