Ecology of the North Cascades

North Cascades
The North Cascades are high and rugged with varied conifer species.
Ecology
Realm	Nearctic
Geography
Country	United States Canada
State	Washington British Columbia

The Ecology of the North Cascades is heavily influenced by the high elevation and rain shadow effects of the mountain range. The North Cascades is a section of the Cascade Range from the South Fork of the Snoqualmie River in Washington, United States, to the confluence of the Thompson and Fraser Rivers in British Columbia, Canada, where the range is officially called the Cascade Mountains but is usually referred to as the Canadian Cascades. The North Cascades Ecoregion is a Level III ecoregion in the Commission for Environmental Cooperation's classification system.^[1]

The terrain of the North Cascades is composed of high, rugged mountains. It contains the greatest concentration of active alpine glaciers in the conterminous United States and has a variety of climatic zones. A dry continental climate occurs in the east and mild, maritime, rainforest conditions are found in the west. It is underlain by sedimentary and metamorphic rock in contrast to the adjoining Cascades which are composed of volcanics.^[2]

The North Cascades has a diversity of plant and animal species.^[3] It contains more than 1630 vascular plant species.^[4] The range has a number of top predators, including bald eagles, wolves, grizzly bears, mountain lions and black bears.^[3] The range is home to at least 75 species of mammals and 200 species of birds that either pass through or use the North Cascades for a breeding area. There are also 11 species of fish on the west side of the Cascades.^[3] Examples of amphibian species occurring in the North Cascades include the western toad (Bufo boreas) and the rough-skinned newt (Taricha granulosa).^[5]

The ecology of the area can be understood by following a west-to-east line at the southern end of the North Cascades, at approximately 47.5 degrees north. As the line passes through the Cascade range, it passes through a number of ecoregions, first getting higher and colder, then getting warmer, yet drier. Each of these component ecoregions can be described by either a tree indicator species, or by a lack of trees: western hemlock, Pacific silver fir, subalpine mountain hemlock, alpine, subalpine fir, and grand fir/Douglas fir.^[6]

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There's a lot of ideas that we just assume we know a lot about because we hear about them all the time. For instance, I know what Pop music is, but if you were to corner me at a party and say, "HANK, What is Pop Music?", I'd be like, "It's uh... it's like, uh... the music that plays on the pop station?" Just because we're familiar with a concept does not mean that we actually understand it. Ecology's kind of the same way: even though it's a common, everyday concept, and ecosystem is a word that we hear a lot, I think most of us would be little stumped if somebody actually asked us what an ecosystem is or how one works, or why they're important, etc. I find it helps to think of an ecosystem, a collection of living and nonliving things interacting in a specific place, as one of those Magic Eye posters, for those of you who were sentient back in 1994. An ecosystem is just a jumble of organisms, weather patterns, geology and other stuff that don't make a lot of sense together until you stare at them long enough, from far enough away, and then suddenly a picture emerges. And just like with Magic Eye posters, it helps if you're listening to Jamiroquai while you're doing it. So, the discipline of ecosystem ecology, just like other types of ecology we've been exploring lately, looks at a particular level of biological interaction on Earth. But unlike population ecology, which looks at interactions between individuals of one species, or community ecology, which looks at how bunches of living things interact with each other, ecosystem ecology looks at how energy and materials come into an ecosystem, move around in it, and then get spat back out. In the end, ecosystem ecology is mostly about eating, who's eating whom, and how energy, nutrients and other materials are getting shuffled around within the system. So today, we're setting the record straight! No more not understanding how an ecosystem works! Starting NOW! So, ecosystems may be a lot like Magic Eye posters, but the way that they're not like a Magic Eye poster is in the way that posters have edges. Ecosystems... I'll just come out and say it: No edge. Only fuzzy, ill-defined gradients that bleed into the ecosystems next door. So actually defining an ecosystem can be kind of hard. Mostly it depends on what you want to study. Say you're looking at a stream in the mountains. This stream gets very little sunlight because it's so small that the trees on its banks totally cover it with shade. As a result, very few plants or algae live in it, and if there's one thing that we know about planet Earth it's that plants are king. Without plants, there are no animals. But somehow there's a whole community of animals living in and around this mountain stream, even though there are few plants in it. So what are the animals doing there, and how are they making their living? From the land, of course! From the ecosystems around it. Because no stream is an island. It isn't there all by itself. All kinds of food, nutrients and other materials drop into the stream from the trees or are washed into it when it rains, leaves and bugs, you name it, flow down from neighboring terrestrial ecosystems. And that stuff gets eaten by bigger bugs, which get eaten by fish, which in turn are eaten by raccoons and birds and bears. So, even though the stream's got its own thing going on, without the rest of the watershed, the animals there wouldn't survive. And without the stream, plants would be thirsty and terrestrial animals wouldn't have as many fish to eat. So where does the ecosystem of the stream start and where does it end? This is a perennial problem for ecologists. Because the way it works, energy and nutrients are imported in from someplace, they're absorbed by the residents of an ecosystem, and then passed around within it for a little while, and then finally passed out, sometimes into another ecosystem. This is most obvious in aquatic systems, where little streams eventually join bigger and bigger waterways until they finally reach the ocean, this flow is a fundamental property of ecosystems. So, at the end of the day, how you define an ecosystem just depends on what you want to know. If you want to know how energy and materials come in, move through, and are pooped out of a knot in a tree that has a very specific community of insects and protists living in it, you can call that an ecosystem. If you want to know how energy and materials are introduced to, used and expelled by the North Pacific Gyre, you can call that an ecosystem. If you want to know how energy and materials move around a cardboard box that has a rabbit and a piece of lettuce in it, you can call that an ecosystem. I might tell you that your ecosystem is stupid, but go ahead! Do whatever you want! The picture you see in an ecosystem's Magic Eye is actually dictated by the organisms that live there and how they use what comes into it. An ecosystem can be measured through figuring out things like its biomass, that is, the total weight of living things in the ecosystem, and its productivity, how much stuff is produced, and how quickly stuff grows back, how good the ecosystem is at retaining stuff. And of course, all these parameters matter to neighboring ecosystems as well because if one ecosystem's really productive, the ones next door are going to benefit. So first things first, where do the energy and materials come from? And to be clear, when I talk about "materials," I'm talking about water or nutrients like phosphorous or nitrogen, or even toxins like mercury or DDT. Let's start out by talking about energy, because nothing lives without energy, and where organisms get their energy tells the story of an ecosystem. You remember physics, right? The laws of conservation state that energy and matter can neither be destroyed or created. They can only get transferred from place to place to place. The same is true of an ecosystem. Organisms in an ecosystem organize themselves into a trophic structure, with each organism situating itself in a certain place in the food chain. All of the energy in an ecosystem moves around within this structure, because when I say energy, of course I mean food. For most ecosystems, the primary source of energy is the sun, and the organisms that do most of the conversion of solar energy into chemical energy...you know this one. Who rules the world? The plants rule the world. Autotrophs like plants are able to gather up the sun's energy, and through photosynthesis, make something awesome out of it: little stored packets of chemical energy. So whether it's plants, bacteria or protists that use photosynthesis, autotrophs are always the lynchpin of every ecosystem, the foundation upon which all other organisms in the system get their energy and nutrients. For this reason, ecologists refer to plants as primary producers. Now, obviously, the way that energy gets transferred from plants to animals is by an animal eating the plant. For this reason, herbivores are known as primary consumers, the first heterotrophs to get their grubby paws on that sweet, sweet energy. After this stage in the trophic structure, the only way to wrestle the solar energy that was in the plants that the herbivore ate is to, you guessed it, eat the herbivore, which carnivores, known as secondary consumers, are very happy to do. And assuming that the ecosystem is big enough and productive enough, there might even be a higher level of carnivore that eats other carnivores, like an owl that eats hawks, and these guys are called tertiary consumers. And then there are the -vores that decompose all the dead animal and plant matter, as well as the animal poop: detritivores. These include earthworms, sea stars, fiddler crabs, dung beetles, fungi, and anything else that eats the stuff that none of the rest of us would touch with a 3-meter pole. So, that's a nice, hierarchical look at who's getting energy from what or whom within an ecosystem. But of course, organisms within an ecosystem don't usually abide by these rules very closely, which is why these days, we usually talk about food webs, rather than food chains. A food web takes into consideration that sometimes a fungus is going to be eating nutrients from a dead squirrel, and other times squirrels are going to be eating the fungi. Sometimes a bear likes to munch on primary producers, blueberry bushes, and other times it's going to be snacking on a secondary consumer, a salmon. And even the tippy tippy top, predators get eaten by stuff like bacteria in the end, which might or might not be the same bacteria that ate the top predator's poopies. Circle of Life! It's also worth noting that the size and scope of the food web in an ecosystem has a lot to do with things like water and temperature, because water and temperature are what plants like, right? And without plants, there isn't going to be a whole lot of trophic action going on. Take, for example, the Sonoran desert, which we've talked about before. There aren't very many plants there, compared to, say, the Amazon rainforest. So the primary producers are limited by the lack of water, which means that primary consumers are limited by lack of primary producers, and that leaves precious few secondary consumers, a few snakes, some coyotes and hawks. All this adds up to the Sonoran not being a terribly productive place, compared to the Amazon at least, so you might only get to the level of tertiary consumer occasionally. Now, all this conversation about productivity leads me to another point about ecosystem efficiency. When I talk about energy getting passed along from one place to another within an ecosystem, I mean that in a general sense, organisms are sustaining each other, but not in a particularly efficient way. In fact, when energy transfers from one place to another, from a plant or a bunny or from a bunny to a snake, the vast majority of that energy is lost along the way. So, let's take a cricket. That cricket has about 1 calorie of energy in it. And in order to get that 1 calorie of energy it had to eat about 10 calories of lettuce. Where did the other 9 calories go? It is not turned into cricket flesh. Most of it is used just to live, like to power its muscles, or run the sodium potassium pumps in its neurons, it's just used up. So only the 1 calorie of the original 10 calories of food is left over as actual cricket stuff. And then, right after his last meal, the cricket jumps into a spider web and is eaten by a spider, who converts only 10% of the cricket's energy into actual spider stuff. And don't get me started on the bird that eats the spider. This is not an efficient world that we live in. But you want to know what's scary-efficient? The accumulation of toxins in an ecosystem. Elements like mercury, which are puffed out the smokestacks of coal-fired power plants, end up getting absorbed in the ocean by green algae and marine plants. While the tiny animal that eats the algae only stores 10% of the energy it got, it keeps 100% of the mercury. So as we move up the chain, each trophic level consumes ten times more mercury than the last, and that's what we call bioaccumulation. Concentrations get much higher at each trophic level, until a human gets a hold of a giant tuna that's at the top of the marine food chain, and none of that mercury has been lost. It's all right there in that delicious tuna flesh. Because organisms only hold on to 10% of the energy they ingest, each trophic level has to eat about 10 times its biomass to sustain itself. And because 100% of the mercury moves up the food chain, that means that it becomes 10 times more concentrated with each trophic level it enters. That's why we need to take the seafood advisories seriously: as somebody who could eat anything you wanted, it's probably safest to eat lower on the food chain, primary producers or primary consumers. The older, bigger, higher in the food chain, the more toxic it's going to be. And that's not just my opinion, that's ecosystem ecology! Thank you for watching this episode of Crash Course Ecology. And thank you for everyone who helped us put this episode together. If you want to reviews any of the topics we went over today, there's a table of contents over there that you can click on. And if you have any questions or comments for us we're on Facebook or Twitter, or of course, down in the comments below. We'll see you next time.

Western Hemlock Ecoregion

The Western Hemlock Ecoregion huddles in the lower west-side elevations of the North Cascades. Western hemlock is found from sea level up to 2,500 feet (800 m) in elevation.^[6] In the Alpine Lakes Wilderness this ecoregion can be found in the lower elevations around 1,000 to 2,000 feet (300 to 600 m)^[7] The average annual temperature is 47 °F (8 °C) and it gets between 70 and 300 centimetres (30 and 120 in) in precipitation per year.^[6] This ecoregion is evidenced by the dense stands of western hemlock, Douglas fir, western red cedar and red alder.^[7] The understory is primarily composed of salal, hazel, salmonberry, devil's club and Oregon grape.^[7] The western hemlock (Tsuga heterophylla) is an extremely shade tolerant tree and it is common to find its seedlings and saplings in the understories of the forest floors.^[6] It prefers moist temperate conditions. As conditions get drier and colder they don't fare as well.^[6] Western hemlocks can reach over 200 feet (60 m) in height with a diameter of 3 to 4 feet (0.9 to 1.2 m).^[6] They can be identified by their drooping leader at the top of the tree.^[6] It is not uncommon to find western hemlocks growing in a row on a nurse log.^[6] The Western Hemlock Ecoregion offers an abundance of life. Black-tailed deer graze in their understories.^[6] Fox, coyotes, cougars, and an assortment of herbivore mammals and birds can also be found in these low elevation forests.^[6]

Silver Fir Ecoregion

The mid-elevation forests in the North Cascades with an elevation between 2,000 and 4,300 feet (600 and 1,300 m) is the Silver Fir Ecoregion.^[6] The Silver Fir Ecoregion makes up for much of the valleys in the Alpine Lakes area. The average annual temperature in this ecoregion is 42 °F (6 °C) and the average precipitation in centimeters is between 220 and 280 centimetres (87 and 110 in).^[8] Typical montane forests in this ecoregion is dominated by Pacific silver fir and also contains noble fir, Douglas fir, and Alaska yellow-cedar.^[6]^[8] Coarse woody debris is very characteristic of the Silver Fir Ecoregion, providing microsites for organisms. The Pacific silver fir zone is in some of the steepest parts of the topography and heavy snow often leads to avalanche gullies.^[6] In every major drainage basin along the western slopes of the Cascade Mountains there is evidence of avalanche tracks breaking up the forested vegetation with nonforested vegetation.^[6] These gullies provide sites of new successional growth as they move toward a coniferous forest again.^[6] Because of the dense forests of the Silver Fir Ecoregion, it was the preferred area for commercial logging prior to designation of areas as wilderness.

The Pacific silver fir (Abies amabilis) is extremely tolerant of shade and does not fare as well in drought or warmer temperatures.^[9] It can grow as high as 180 feet (55 m) and reach 3–5 feet (0.9–1.5 m) in diameter.^[6] The understory communities of the Pacific silver fir can vary depending on moisture availability.^[6] Common understory shrubs include the vine maple, salal, Cascade Oregon grape, blueberry, mountain huckleberry, devil's club, and fool's huckleberry.^[6] Common understory herbs are bear grass, twin flower, pipsissewa, dwarf dogwood or bunchberry, bead lily, trailing blackberry, low false Solomon's seal, foam flower, trillium, oak fern, and lady fern.^[6] The microclimate of the understory is moderated by the forest canopy causing the conditions to be cooler and moister in the summer and warmer in the winter.^[9] Pacific silver fir seedlings and saplings are often found growing under their own canopies or those of a mixed canopy forest.^[6] Along streams in this ecoregion, breaks in the forest are replaced by mountain alder, willow and vine maple and herbs such as saxifrage, yellow willow-herb, monkey flowers, and bluebells can be found.^[6] Mountain alder and vine maple can also be found around lake edges and in areas of flat or gentle slopes, bogs, or marsh habitat.^[6] Examples of Pacific silver fir forests can be found in the Commonwealth Basin and the Snow Lake areas of the Alpine Lakes Wilderness.^[6]

Subalpine Mountain Hemlock Ecoregion

Moving up in elevation from the Silver Fir Ecoregion, between about 4,000 and 5,400 feet (1,200 and 1,600 m) on the west side of the Cascade Range, the ecoregion shifts to the Subalpine Mountain Hemlock Ecoregion.^[6] This ecoregion has a colder annual average temperature of 39 °F (4 °C) with average annual precipitation between 160 and 280 centimetres (60 and 110 in).^[8] This ecoregion consists of mountain hemlock forests, subalpine meadows, streams, lakes, wetlands and avalanche gullies creating distinct patterns of new succession.^[8] In the lower ends of this ecoregion there are continuous closed canopy forests while the higher reaches will see mosaics of meadows with patches of mountain hemlock forests.^[8] The mountain hemlock forests consist of mountain hemlock, subalpine fir, Alaska yellow-cedar, and Pacific silver fir.^[8] Washington's alpine and subalpine areas account for about 4.4% of its total land area.^[10]

Progressing upward from the gradient of Silver Fir and Mountain Hemlock ecoregions, the mountain hemlock (Tsuga mertensiana) tends to become the dominant conifer, although it may codominate with the Alaska cedar and Pacific silver fir. Mountain hemlock trees live as long as 1000 years: longer than the Pacific silver fir. Trees between 500 and 700 years may be 100 to 125 feet (30 to 40 m) tall.^[6] Hemlock cones are about 2–3 inches (5–8 cm) in length and develop at the ends of branches.^[6] These conifers are easy to distinguish amongst the others with their dense grayish-green needles.^[6] According to Franklin and Dyrness, the understory where the mountain hemlock and Pacific silver fir co-dominate is dominated by tall mountain huckleberry; where the Alaska cedar dominates, the understory is dominated by dense collage of rhododendron, huckleberry and mountain ash.^[6]

In the higher boundaries of subalpine ecosystem, where the abiotic conditions are more stressful, trees are clumped together in patchy islands. Trees in this area can be recognized by its krummholz form. Trees of this upper boundary will take on a flag appearance with branches extending from one side indicating the prevailing wind directions. The skirt height of the trees is indicative of the height of snow cover where branches tend not to grow.^[6] There are various reasons as to why these trees take this form. Strong winds combined with ice particles will cause abrasion scouring the waxy cuticle from one side of the tree creating damage that will prevent branch formation and growth.^[6] In addition, the wind will cause desiccation and evaporation in the needles causing branches to die on this side of the trees.

Scattered amongst the island patches of trees in the upper boundaries are parkland areas with showy meadows. Events such as fire, avalanches, snow slumping and climate change make the boundaries of these areas and the balance of trees and meadows dynamic.^[10] The forest islands typically consist of mountain hemlock, subalpine fir, and Alaska cedar.^[6] Often there are invasions of trees into meadow areas and this reached a peak in the 1930s due to considerable warming.^[6] Invasions of meadows by trees can also occur with disturbances.

The beauty of meadows is very popular amongst hikers. Wildflowers that are found in this ecoregion are the tiger lily, glacier lily, bead lily, queen's cup, columbine, aster, trillium, pearly everlasting, valerian, skyrocket, shooting star, penstemon, lousewort, mountain bog gentian, monkey flower, monkshood, bluebell, bellflower, bleeding heart, Tweedy's lewisia, balsamroot, wild orchids and more.^[11] The wildflowers are at their peak in the meadows and along streams from mid-July to mid-August.^[11] The parklands of the Mountain Hemlock Ecoregion draw their distinct characteristics from the climate and topography.^[6]

The two dominant vegetation types of this mountain region, forests and meadows, have very distinct differences in their microclimates. The amount of solar radiation and UV exposure can vary substantially in our northern latitude largely based on the time of day, slope, season, cloud cover and vegetation.^[6] Temperatures adjust accordingly to this solar radiation and exposure. The parklands of this montane region have a much larger range of temperatures as compared to the hemlock forests.^[6] The range can be as much as 50 °F (28 °C) while the range in the forests rarely exceeds 20 °F (11 °C).^[6] This is due to the canopy of the trees, creating a much more protected environment as compared to the open meadows. In addition soil temperatures directly impact biological activity affecting soil organisms and root systems.^[6] Daily and season temperature changes greatly affect the soils' heat loss and gain.^[6] However, the snowpack acts as an insulating buffer against temperature change in soils.^[6] The mountain hemlock forests are the wettest and coldest of the Cascade forest zones.^[6]

In the richness of this region many animal species pass through this zone at least one season a year such as mountain goat, black-tailed deer, American black bear, elk, cougar, and many bird species.^[6] Only the whistling hoary marmot is restricted to alpine and subalpine areas.^[6] Besides the richness of mammals there is a richness of insects that are integral to the abundance of flowering plant species in this area.^[6] Another important pollinator in this area is the hummingbird.^[6] There is still much to be researched and discovered to better understand species interactions and reliance in both the alpine and subalpine ecosystems.

Alpine Ecoregion

The Alpine Ecoregion makes up much of the North Cascades. Alpine areas such as this are rugged with rocky ridges, snowfields, partially vegetated terrain, and are above the natural treeline.^[10] The timberline in the Alpine Lakes Wilderness is found at approximately 6,000 feet (1,800 m).^[7] The average annual temperature is 37.5 °F (3 °C) with only a mean annual precipitation of 46 centimetres (18 in).^[8] These conditions along with winds and blowing ice are not conducive for trees. Because of the extreme temperatures and low precipitation there are few plant species as compared to lower elevation ecosystems and they are simpler in structure.^[7] However, precipitation, or lack thereof, is a more important limiting factor than temperature.^[7] Both plant and animal species have adapted in many different ways to deal with this challenging environment.

This high elevation habitat of high winds, prolonged snow cover, steep terrain, high temperature variability, and intense UV radiation lead to special species adaptations.^[10] Alpine regions generally have hypoxic conditions that lead to additional energy expenses for organisms.^[10] Increased elevations usually lead to shorter breeding season in animals, as is the case in the alpine ecosystems in the North Cascades. In addition to the shorter breeding season, wildlife often requires seasonal movement to different elevations in order to find adequate food and habitat.^[10] However, species such as the white-tailed ptarmigan, hoary marmots, and pikas remain in high elevations of the Cascades year round left only to go to patchy and scattered alpine vegetation. The majority of species will move to lower elevations at some time throughout their life history. Adaptations such as torpor in hummingbirds, the ability of mountain goats and coyotes to camouflage in the landscape, animals developing extra fat deposits, and the raptor's ability to move efficiently in the strong winds illustrate just some of the ways species have been ability to cope with alpine conditions.^[10] The white-tailed ptarmigan has an adaption of changing its plumage from white in the winter to brown in the summer in order to camouflage.^[10] Many species in higher elevations produce fewer offspring than in lower elevations but spend more time nurturing their young.^[10]

While alpine ecosystems provide challenging abiotic conditions for species there are advantages to animal species to habituate these areas. In the winter while there is extensive snow pack there are also strong winds that will expose herbaceous stems and seeds for animals to forage on.^[10] Insects that are blown up from lower elevations will land on the snow beds in the spring offering much nutrition for birds and other mammals that breed in the alpine.^[10] When snowfields melt it creates a gradient of plant phenology which provides emerging vegetation over a period of time for herbivores to feed on and migrate along this line. Spring foraging is believed to be crucial in the breeding in a number of species such as the mountain goat.^[10] Leaf budding and fruiting in late summer past the edges of snowfields also offer food for the animals that depend on this area.^[10] Black bears, songbirds and marmots in the North Cascades and Alpine Lakes can find cover in lush vegetation in avalanche chutes adjacent to the subalpine forests.^[10] There seems to also be evidence that there is a lower rate of parasitism and disease in these high alpine elevations offering yet another advantage to alpine species. The alpine grouse is one example of an alpine animal that has few blood infections or intestinal parasites.^[10] Other animal species in the summer months will migrate into the higher alpine elevations to avoid insects and forage in the meadows.^[10]

Subalpine Fir Ecoregion

The Subalpine Fir Ecoregion, descending down the east-side of the Cascade Range, reaches elevations between 4,200 and 6,000 feet (1,300 and 1,800 m).^[8] This area has the same mean annual temperature of 39 °F (4 °C) as the Mountain Hemlock Ecoregion, but a drastically lower annual average precipitation of between 100 and 150 centimetres (40 and 60 in) with a much larger portion falling as snow rather than as rain.^[8] The ecosystems in this ecoregion are the subalpine fir forests, subalpine meadows, avalanche gullies, and freshwater wetlands, streams and lakes.^[8]

The subalpine fir forests in the North Cascades include Douglas fir, Engelmann spruce, subalpine larch, and whitebark pine.^[8] The Engelmann spruce and the subalpine fir are commonly found together. In the higher boundaries of this ecoregion the subalpine fir takes on the krummholz form. The Subalpine Fir Ecoregion is characterized by its patches of forest and meadows in its upper range similarly to the Mountain Hemlock Ecoregion.^[7]

Grand Fir/Douglas Fir Ecoregion

Descending down the east side of the Cascade Range is the Grand Fir/Coast Douglas-fir Ecoregion with a very diverse forest. This forest has the most diverse trees of the forested ecoregions in Washington state which includes grand fir, Douglas fir, Engelmann spruce, subalpine fir, ponderosa pine, lodgepole pine, western white pine, whitebark pine, western larch, and subalpine larch. This ecoregion has an annual mean temperature of 46 °F (8 °C) and receives between 60 and 110 centimetres (24 and 43 in) of precipitation per year.^[8] The elevation range of this ecoregion is between 2,000 and 5,000 feet (600 and 1,500 m).^[8]

In the upper regions of this ecoregion, the dominant conifers are the mountain hemlock and subalpine fir and in the lower boundary the grand fir and Coast Douglas-fir dominate.^[7] There is a variety of understory vegetation in this ecoregion that includes pinegrass, elk sedge, sedges, low shrubs, vine maple, white alder, and huckleberry.^[7] This diverse landscape offers habitat to many species including grazers such as deer, elk, black bear, herbivores, and a variety of birds.

Fauna

A variety of reptiles, amphibians, mammals, birds and arthropods are found in the North Cascades. A small number of grizzly bears (Ursus arctos horribilis) inhabit the far northern Cascades, near the Canada–United States border.^[12] A breeding pack of wolves was confirmed in Okanogan County in 2008, the first such pack in Washington state since the 1930s.^[13] Other predator species include mountain lions, black bears,^[3] fishers, and wolverines.^[14]

Over 75 species of mammals occur in the range, including the mountain goat that lives in the high alpine tundra.^[3] Bird species include the bald eagle, osprey, and harlequin duck.^[14] Examples of amphibians occurring in the North Cascades include the western toad, Bufo boreas, and the rough-skinned newt, Taricha granulosa.^[5] An unusual feature of the rough-skinned newt populations is that approximately ninety percent of the adult population is perennibranchiate.^[15]

References

^ "Ecological Regions of North America, Level I-III" (PDF). Commission for Environmental Cooperation. Retrieved April 6, 2009.
^ "Level III ecoregions" (PDF). Western Ecology Division. U.S. Environmental Protection Agency. Retrieved March 11, 2009.
^ ^a ^b ^c ^d ^e Kefauver, Karen (September 15, 2010). "North Cascades National Park: Wildlife". GORP. Orbitz. Archived from the original on April 27, 2012. Retrieved June 6, 2012.
^ "Plants". North Cascades National Park. National Park Service. May 16, 2012. Retrieved June 6, 2012.
^ ^a ^b Rawhouser, Ashley K.; Holmes, Ronald E.; Glesne, Reed S. (2009). "A Survey of Stream Amphibian Species Composition and Distribution in the North Cascades National Park Service Complex, Washington State" (PDF). Archived from the original (PDF) on October 16, 2011. Retrieved June 7, 2012.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p ^q ^r ^s ^t ^u ^v ^w ^x ^y ^z ^aa ^ab ^ac ^ad ^ae ^af ^ag ^ah ^ai ^aj ^ak ^al ^am ^an ^ao ^ap ^aq ^ar Kruckeberg, Arthur (1991). The Natural History of Puget Sound Country. University of Washington Press. ISBN 0-295-97477-X.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ Alpine Lakes Area Land Management Plan (Report). USDA Forest Service. 1981.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m Gold, W. (January 28, 2008). "BIS258 lecture notes" (PDF). University of Washington. Retrieved March 15, 2009.
^ ^a ^b "Pacific Silver Fir" (PDF). Washington Department of Natural Resources. Archived from the original (PDF) on May 23, 2011. Retrieved March 11, 2009.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j ^k ^l ^m ⁿ ^o ^p Johnson, D.H.; O’Neil, T.A. (2001). Wildlife Habitat Relationships Washington and Oregon. Oregon: Oregon State University Press. ISBN 0-87071-488-0.
^ ^a ^b Smoot, Jeff (2004). Backpacking Washington's Alpine Lakes Wilderness. Helena, Montana: The Globe Pequot Press. ISBN 0-7627-3098-6.
^ "Grizzly Bears In the USA and the North Cascades: Past and Present". Grizzly Bear Outreach Project. Archived from the original on January 8, 2008. Retrieved August 24, 2009.
^ "Gray Wolf Conservation and Management". Washington Department of Fish & Wildlife. Retrieved May 8, 2011.
^ ^a ^b "Animals". North Cascades National Park. National Park Service. Retrieved June 6, 2012.
^ Hogan, C. Michael (2008). Nicklas Stromberg (ed.). "Rough-skinned Newt (Taricha granulosa)". Globaltwitcher. Archived from the original on May 27, 2009. Retrieved May 21, 2009.

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