The soft, spongy earth sinks and swells beneath my feet. Branches and needles tower overhead from trunks of various sizes and shapes, diffusing the light and casting shadows. The edges of grasses and herbs slip past my ankles, while shrubs tickle my things and hips. All the while an orchestra of whistles and sing-song sounds float on the wind, and a bouquet of sweet and musty smells rise and fall from the ground. Step, climb, dip, and try not to trip—this is what it is like to hike through a forest.
When I met up with Corbin Murphy, BLM Wildlife Biologist, at the Crabtree Lake Trailhead, I knew that I was in for an adventure. The plan was to follow a trail down into the Crabtree Lake Valley, and then bushwack into the woods to reset some camera traps that needed tending to. We would eventually make it down to Crabtree Lake to one of the oldest forests in Oregon. I knew that walking would be a bit rough, but the payoff was worth it. I was right.
The Hike
- Trailhead: Crabtree Valley Trailhead
- Distance: 4-5 miles
- Elevation Gain: about 900 ft
- Details: Roads to the trailhead are gravel but in decent condition. The last half mile of road is rough, but I made it with my Honda Civic. The usual route for this hike follows a decommissioned road down. Take a sharp right once you reach a road and follow it up to Crabtree Lake.
Diverse Species
Entering a forest should be a rich, multisensory experience—an orchestra of sights, sounds, and scents. It should be a tangled web of life! Complex ecosystems are not only more aesthetically pleasing, but they also tend to be resilient and functional.
Paying attention to the diversity of species in an ecosystem is an important part of being a wildlife biologist. So, as Corbin and I began our hike along an old decommissioned road heading down toward Crabtree Valley, he was on high alert for the sights and sounds of the forest. It didn’t take long before we started talking about the different plants and animals we were seeing and hearing on the trail.
Sounds of Life
Listening for birds was of particular interest to Corbin. He pointed out the high pitched electronic sounding whistle of a varied thrush and two-note chirp-chirp of a flycatcher. Because many birds are shy and difficult to spot in a forest, wildlife biologists often use bird calls to count birds instead of relying on visual identification.
As part of his work, Corbin shared how he has been participating in breeding bird point-count surveys recently. To conduct this kind of survey you drive along a transect an hour before dawn, stopping every half-mile for two minutes to listen, and identify bird calls. Point-counts are useful for biologists because they give us a better idea of what species are present in an ecosystem, and over time can see declines in specific species populations as well.
Green Stuff
In addition to birds, the variety of plant life also attracted our attention. Corbin pointed out several species of wildflowers, shrubs, and trees—you know, all the pretty green stuff.
It is easy to appreciate the importance of green stuff (a.k.a. plants) to an ecosystem. From an early age, we learn that plants provide oxygen to breathe and food to eat. But not all plants are equal. Like animal species, each species of plant has its own role to fulfill in the ecosystem. In some cases, providing special benefits to select species. Thus, we need a diversity of plant life to support the diversity of life in an ecosystem.
When it comes to conifer forests, less abundant deciduous trees and shrubs play a disproportionately large role in supporting the ecosystem. According to Corbin, conifer needles are generally not very nutritious. They have a low energy density, making them unable to support many invertebrate species. In contrast, deciduous trees and shrubs make a lot more energy available to support an abundance of species.
Biological Desert
According to Corbin, a forest is more than just trees. A forest should have an understory of shrubs and forbs. In a natural system, stochastic disturbances, like forest fires, allow for the establishments of an understory. High-density tree plantations do not. Corbin explained, “shrubs and forbs compete with seedlings. So they will establish, and they can dominate a site for anywhere from 30 to 300 years.” This stage of the forest is called “early seral” and is an important stage of forest development.
However, in a tree plantation, this long period of competition is undesirable. Instead, a more profitable high-density forest is established, and the early seral stage of forest development is shortened or eliminated. This creates “a biological desert,” said Corbin, “You have conifer trees and hardly any understory—any vegetation at all. You can literally count the number of plants and animals on one hand.”
That is why managing forests, like that surrounding Crabtree Lake, requires an eye for biodiversity. Forest density and early seral species should be considered. We don’t just need a bunch of any kind of plant, but we need an assortment of plants.
Look-Alike
Of course, even between deciduous understory trees, diversity of species is important. When hiking through a forest, it is easy to be blind to plant diversity. Everything can seem nondescript in a wash of greenery. But with a keen eye, even close look-alike species can be distinguished from one another.
As we walked through a tunnel of deciduous trees and shrubs, Corbin pointed out a couple of look-alike pairs of species hidden in the foliage.
One of the pairs that sat side-by-side was the Vine Maple and Rocky Mountain Maple also called Douglas Maple. Though very similar looking in size and general shape, vine maples tend to have more lobes, usually nine, than Rocky Mountain Maple, usually three. Also, the Rocky Mountain Maple’s leaves have sharply toothed margins, while the Vine Maple’s leaves’ margins are doubly toothed.
Red Alder and Sitka Alder were another pair of look-alikes found on the trail. Again, though similar looking at first glance, the growth form of the Red Alder is straighter and taller, while the Sitka Alder is shorter and more shrubby. Also, if you look closely at the leaves, the Red Alders’ leaf margins roll under slightly, while the Sitka Alders’ leaf margins are sharply toothed.
All this to say, there are a lot of different kinds of green-stuff in a forest.
A Special Place
Before dropping down toward the lake, Corbin and I stopped to look down at where we were headed. Corbin explained that we were about to enter a really special place. Perhaps one of the oldest forests in Oregon, the Crabtree Lake Valley, and surrounding areas, are all part of the Crabtree Valley Complex—“An Area of Critical Environmental Concern (ACEC) due to its outstanding geological, recreational, and ecological value.”
Crabtree Valley was created during the last ice age. Glaciers carved out large amphitheater-like valleys, called cirques, which protected much of the forest from fire for perhaps 1,000 years. Later, for whatever reason, it remained unlogged. Making it a perfect example of a late-successional forest and refuge for species, like the Northern Spotted Owl.
So when the BLM acquired the land in the 1980s, it fell under ACEC status and a management plan was put in place in order to protect its values. Which brings us to today where it is still under a resources management plan as a late-successional reserve.
Management to Protect
One of the ways the BLM has been working to meet the goals of the resource management plan is by reducing roadways in the area. Though some areas within the Crabtree Lake Complex were never logged, logging was still rampant in the region. In fact, the first part of our hike was on an old logging road through an area that was probably logged in the 70s or 80s.
So in order to enhance and restore what we might expect from a late-successional reserve, the BLM decommissioned most of the roads, ripped them up, put in waterbars, and took out culverts—all efforts to restore the natural functions of the forest.
Give a Hoot
Eventually, we made our way down to the lower valley floor and into the late-successional forest reserve. Here we took a sharp left onto another road Corbin said he usually uses to access the property. He also told me that the road is where the BLM does surveys for Northern Spotted Owl. Every half-mile along the road is a survey station where a biologist will stop for 10 minutes to call and listen for spotted owls.
There are two pairs of spotted owls reported within the watershed, Corbin said, because “the habitat is so great in this area.” This is unusual because spotted owls usually need a 1.2 mile home range in the Cascades, but these nesting pairs are only about a half-mile apart. Not only that, but last year the pairs each had two juveniles. Which is remarkable because, as Corbin explained, “other than that, there was zero reproduction in spotted owls from Sweet Home in the BLM up to the Columbia River.”
Wear Layers
Continuing down the road, the dynamics of the forest opened up— there were tall douglas-fir trees and hemlock; open areas with shrubs and smaller trees; and snags and down logs.
“One of the big things about late-successional forests too is the structure,” said Corbin. You want to see “horizontal and vertical heterogeneity” in a late-successional forest.
Basically, a forest like the one we were observing, starts with a lot of Douglas-fir, but then over the next hundred years, holes open up in the canopy that allows shrubs and shade-tolerant trees, like hemlock, to grow and fill in gaps.
This development of structure is important because it creates habitat for wildlife. A forest that lacks diverse forest structure is simply not conducive to the wildlife that needs late-successional forest.
Corbin told me about a transect study that looked at how flying squirrels fared when there were big trees, but no holes for shrubs and smaller trees available for the development of an understory. The squirrels had the big trees they needed for food and nesting, but there was not enough cover for them to avoid predation. Needless to say, the outcome wasn’t great for the squirrels
A Rotten Heart
At one point, Corbin and I came across a down tree with heart rot. Which brings me to another component of late-successional forest that adds to its complexity— dead stuff.
If the down tree with heart rot was actually standing, or a snag, it would provide habitat for cavity nesters like woodpeckers. As a large down log, it creates habitat for hundreds of invertebrates, bacteria, and fungi, as well as amphibians.
The importance of dead trees cannot be overemphasized. In fact, often land managers create snags by girdling trees in an attempt to mimic the natural process of snag formation. Unfortunately, according to Corbin, it generally doesn’t work very well. The natural process is slow, possibly taking a couple of hundred years for a snag to form. There really isn’t a quick way to recreate that.
In addition, Oregon slender salamanders, a species of concern, rely on the late-successional forest for large down wood. This species is endemic to Oregon and is doing O.K. right now, but as timber harvesting continues to produce young 20-30 years old forests, things could get dicey. Less large down wood means less of an important microhabitat that Oregon slender salamanders need to survive.
This is why on federal public lands, Corbin explained, “we are trying to institute measures to have leave trees, and these are the legacy trees from the previous cohort, and those are the ones that have all the lichens and bryophytes—create a little refugium—and those eventually become snags and fall over.”
Leave it to Beaver
Not long after passing the downed log, Corbin and I headed off-trail to check on a beaver dam analog (BDA) that was put in last fall. As we climbed through the underbrush, Corbin explained that beavers were historically present in the wet meadow we were about to visit, pooling the water and creating a much larger lake. We even some old beaver sign to confirm it.
However, when roads were constructed in the area, the beavers disappeared. Corbin hypothesized that they could have been trapped. Since then, trees have started to encroach into the wet meadow, altering the historically flooded area and shrinking the lake.
Then, a couple of years ago, Oregon Department of Fish and Wildlife and BLM joined forces in an effort to reintroduce beavers into the area. Several beavers were released into the watershed. But they didn’t stay.
Now, the BLM is working on a soft release program in the hopes that the next group of beavers they introduce won’t go away. That is why the BLM constructed the BDA—in an effort to make the meadow homier. Once established, beavers, a keystone species, will naturally alter the ecosystem; hopefully, restoring the meadow to historical conditions.
Fishing for Fishers
After visiting the BDA, Corbin and I continued a bit further down the road before making our way back into the woods again. This time we bushwacked our way to one of the camera-traps Corbin needed to reset. The camera traps were set up as part of a Forest Carnivore Research Project started by Katie Moriarty from Oregon State University. The BLM adopted a project grid area, and are working on tracking the carnivores that visit each camera trap site.
The overall goal of the projects is to determine if Pacific Fishers are present in the Western Cascades. Historically, Corbin shared, Pacific Fishers ranged from California up through British Columbia. But their range has shrunk in Oregon over the years and now there is no record of Pacific Fishers anywhere north of Eugene. Later, as part of the carnivore project, Fishers will hopefully be reintroduced into areas like the Crabtree Lake Valley.
As Corbin worked to reset the camera trap and bait it, I asked him about why the reintroduction of Fishers is important. He explained that Fishers are candidate species for ESA listing, which makes them important in the eyes of the government. Candidate species are in danger of extinction in at least part of their range.
Species extinction is a concern because, as mentioned earlier, each species has a role in the ecosystem. Pacific Fishers are top predators. They help regulate populations of organisms that sit below them in the food chain. They are also opportunistic feeders and primarily prey on small mammals, including squirrels and even porcupines. Thus the loss of Fishers could have ripple effects on the forest food web—allowing porcupine populations to increase, for example, which could lead to excessive damage to trees they feed on.
Forest Walking
After resetting the first camera trap, we did some serious bushwhacking up to the next one before heading down to crabtree lake. As we made our way to the lake, I was taken aback by the grandeur of the forest. I felt small beside the mammoth-sized trees, but at the same time, perfectly natural walking across a huge moss-covered log. We were really in the thick of the forest.
Here we did the forest dance—climbing, ducking, and trying not to trip. We saw more life, including a small salamander hiding amongst a pile of old deadwood. We talked about huckleberries that would ripen in late summer. And craned our necks looking up at the tallest trees in the forest.
During the last leg of our hike, the biodiversity of habitat and species was all around us—the promise of spotted owls, flying squirrels, and future fisher. This is what hiking in a forest is all about!
Corbin Murphy is a Wildlife Biologist for the Salem District of Bureau of Land Management. He has been with the BLM for 11 years and currently works in the Cascades Field Office. He has also worked for the U.S. Forest Service.