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Colorado's Ecosystems: Subalpine Forest
This habitat is also called boreal forest or spruce-fir forest, since its dominant trees are Engelmann spruce and subalpine fir. Both of these are high-elevation conifers with pointy tops and short needles. The latter is a distinctive tree with shiny silver bark marked by short horizontal lines. If you are in an area with a good number of large subalpine firs, you can be confident that you are somewhere between about 9,500 and 11,000 feet, in the highest of the true forest zones, traditional home of Boreal Owl, Three-toed Woodpecker, Hammond's Flycatcher, Gray Jay, and Pine Grosbeak. Other birds you could see here include Red and White-winged Crossbills, Dusky Grouse, Mountain Chickadee, Clark’s Nutcracker, and Red-breasted Nuthatch.
Animals at this elevation include porcupine, bear, and elk. The Canada lynx has recently been reintroduced to this habitat, and though its numbers remain small, the initial success of the introduced population is highly encouraging. Butterfly enthusiasts who venture to this altitude may encounter Frigga, Atlantis, Silver-bordered, Bog, and Purple Fritillaries, Scudder’s and Queen Alexandra’s Sulphurs, and Common Alpine.
Treeline is not an abrupt transition in most areas. Rather, as you move up towards and above 11,000 feet, you will notice the spruces and firs becoming noticeably smaller, until they start to assume bush form. This stunted forest is often called the krummholz. The birds in this habitat tend to be a mix of spruce-fir and tundra birds, but the dominant species is definitely White-crowned Sparrow. In some areas, you may be able to find populations of Brewer’s Sparrows breeding in the krummholz, thousands of feet higher than their relatives down in the sagebrush. Some people have proposed that these Brewer’s Sparrows may actually be the same as the “Timberline” Brewer’s Sparrows of Canada, which some believe to be a distinct species.
True subalpine forest is a habitat type that few states south of Canada can boast large tracts of, but Colorado is an exception thanks to its many high mountains. This habitat is best accessed in late summer and early fall, since many of the roads are snowed in at other times of year.