Walk into the forest and make a note of the different tree species you see. On the westside of Washington state, this will likely include Douglas fir, hemlock, cedar and alder and possibly a few others. On the eastside, you are likely to tally Douglas fir, ponderosa pine and grand fir.
Now, from that exact spot in the forest, look around and count the number of shrubby understory, (or “brush”) species that you see. This may include oceanspray, serviceberry, ninebark, salal, salmonberry, red or blue elderberry, cascara, beaked hazelnut, bitter cherry, chokecherry, evergreen huckleberry and so on. Nearly always, there are two to three times as many species of native shrub species on a site than there are tall trees.
This rich, and often overlooked and underappreciated, layer of our forests contains some of the best wildlife habitat out there.
Benefits of Brush
Nearly 25 percent of our forest-dwelling wildlife rely on these plants for food or cover, and would not exist on our lands without these wonderfully dense thickets. Song sparrows, spotted towhee, warblers, chipmunks, deer and so on. The critter list of those that thrive on this critical habitat element is long. In fact, the shrub layer may be the most important habitat feature for a high diversity of wildlife species in early forest successional stages. Systematic research in Oregon has shown that songbird abundance and diversity is increased when replanted forests are allowed to develop some shrub components.
When sunlight reaches the ground, even in small amounts, the various shrub species will take advantage of this niche and grow, sometimes for many years and to impressive mass. Who hasn’t seen a sunlit gap in the wet forest where a little pocket of shrubs has taken hold ? These gaps in the forest canopy are a great source of habitat diversity.
Many shrub species produce “mast,” or fruit, that is eaten by a wide array of wildlife, from birds to the smallest mammals and all the way up to the black bear. The wonderful flowers of our shrub species provide feeding opportunities for pollinators, including hundreds of species of native bees, hummingbirds and butterflies. Unlike the conifer, these flowers produce nectar, a rich draw for many animals including specialized insects. And most of our game species, those big charismatic megafauna, forage on these plants too. Shrubs usually carry these animals through the winter.
There are many shrub (“brush”) superstars. Here we highlight just a few of our best wildlife habitat shrub species.
Blue elderberry (Sambucus cerulea): This lovely plant grows in sunny spots east and west of the Cascade Mountains. It can take on a fairly large form if given enough time and light, reaching up to 25 feet high and across. Multiple stems produce lush, compound foliage that is preferred browse for deer, elk and other animals. The abundant purple berries are favorites of many birds and seldom last long. These same berries can even be made into wine or jam. If you want to enhance wildlife habitat by planting shrubs, this one is a great choice.
Red elderberry (Sambucus raesmosa): Wetter sites in western Washington grow the red elderberry, a very similar plant to the blue, with a branching brushy form and red berries favored by many wildlife species. These grow in small openings and in the dappled understory of mixed forest stands. In my observation these two plants usually don’t occur in the same locations, but both are great wildlife habitat plants.
Salmonberry (Rubus spectabilis): Dominating many understories across western Washington is the ubiquitous salmonberry. This plant features dense woody stems that can create a jungle of dense vegetation — perfect places for birds and small mammals to seek shelter. The berries resemble salmon roe (hence the name) and are eaten by most everything, including people.
Indian plum (Oemleria cerasiformis): Perhaps the earliest blooming shrub species in western Washington is the gorgeous Indian plum. This rich understory species occurs on many moist forest sites, providing early foliage and flowers for native pollinators. They produce lovely, tiny purple fruits and never last long, being eaten at first chance by many birds and mammals. Watch for the white flowers in the first blush of spring.
Black hawthorn (Crataegus douglasii): The spiny hawthorn creates dense cover for birds and a great place for mammals to hide and rest. The fruits (called “haws”) are also eaten by many species. It prefers sun, but will get by in dappled shade. This plant occurs on both sides of the mountains.
Other shrub superstars worth mentioning include serviceberry, mock orange, ceanothus, cascara, salal, willow, dogwood and even devil’s club. Each of these has great wildlife structure and bears fruit.
Sometimes the dense nature of shrub cover can prevent conifers from regenerating for many years, much to the frustration of those attempting to grow trees for harvest. The small landowner, however, usually has mixed objectives: provide quality wildlife habitat AND grow the next crop of trees. These dual objectives can be accomplished by identifying the best wildlife shrub species growing on the property and then actively maintaining them over time by allowing for space to grow these plants. Conifer competition can be dealt with by cutting the competing plants back. Some landowners also use approved herbicides on individual plants or clumps to allow their conifers to get above the shrub layer and form a new canopy.
Planting shrubs can work if one has time to adequately care for each plant. This will include controlling competition and preventing deer and elk from browsing on the young plants. Desired shrubs that become too tall and “leggy” for deer and other browsers to reach leaves and fruits can be simply pruned back.
These are just a examples of the fabulous shrub species we encounter on our forest lands that are worth knowing and keeping on the landscape. Their value to wildlife as habitat is very great and definitely worth managing for.
A longer version of this blog first appeared in the Winter 2016 issue of Forest Stewardship Notes, a free, electronic newsletter published quarterly by DNR and Washington State Forestry Extension. The author, Ken Bevis, is a DNR stewardship wildlife biologist and one of the several DNR staff available to consult with qualifying small forest landowners at no charge.
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