Quote:
Originally Posted by vegaspilgrim
This is more of a vegetation/geology question than a climate question, but because they're interrelated, why does Crested Butte look so different than other areas of the Colorado high country above 10,000 ft? The land there looks so much more "open," smoother, and more barren, with tons of aspen clusters and very little pine trees. I attached two photos I took, one of Crested Butte, one of Silverton (an example of what I think of as more "typical" high country scenery). Do aspen trees thrive in particular types of weather conditions? Last summer I took an amazing road trip through Colorado and New Mexico (route taken included US highways 285, 50, 550, 84) and saw places I hadn't seen since I was a little kid, kind of reinvigorating my interest in Colorado. I think it took four years of living in Arizona to understand how different weather can be depending on what region you're in. Growing up, I never thought much of the "weather" at all-- weather is weather; it's not really anything to complain about or sing about.
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There is a pretty good dividing line in Colorado between what most naturalists call the "Southern Rockies" and the "Central/Northern Rockies." Though it is an imperfect boundary, US Highway 50 is a pretty good dividing line. One of the biggest differences in the two climate regimes is in summer precipitation, with the Southern Rockies being more influenced by the Southwest Monsoon and the Central/Northern Rockies much less so. So, the Southern Rockies get more summer precipitation and the Central/Northern Rockies less. In mid-elevation areas of the Rockies, aspen tends to be the more dominant "sub-climax" species of tree in the Southern Rockies, and lodgepole pine in the Central/Northern Rockies. You will find relatively few large stands of lodgepole south of US 50 in Colorado, while it is very common from there north all the way into Canada.
The San Juan Mountains are somewhat unique in that they are far west enough to catch quite a bit of winter moisture from the Pacific (similar to a lot of the Central/Northern Rockies), but far enough south to catch a lot of the Southwest Monsoon in summer. That makes them kind of a "garden spot" for both aspen and coniferous forests. That, and their geography and geology make them a very special place (where not nearly enough is being done to protect them from crap development) in the Rocky Mountains.
The Crested Butte area, though north of US 50 has characteristics of both the Southern and Central/Northern Rockies. It gets a fair amount of summer precipitation (which encourages aspen), but is drier than the San Juans in summer and is generally much colder in winter. In such colder regimes, especially in Wyoming as an example, aspen will grow in protected areas and on slopes where the temperatures are a little warmer and more moisture accumulates, and sagebrush will grow in the colder, drier, more exposed locations. That happens a lot around Gunnison and Crested Butte. One other thing, in the Southern Rockies, aspen are often the "pioneering" trees, colonizing areas where the coniferous forest has been logged or burned off. In the Central/Northern Rockies that duty often falls to the lodgepole pine. A lot of he coniferous forest around Silverton (and Telluride) was logged off during the early mining days. Also, huge forest fires burned through most of the San Juan mountain region during 1879. Aspen colonized a lot of that, but some areas (around Cumbres Pass on the Colorado/New Mexico border, for example) have never re-forested. Logging, though it occurred, wasn't as big around Crested Butte.
A great book I have cited in another thread describes all of this quite well. It is
A Sierra Club Naturalist's Guide: The Southern Rockies, by Audrey DeLella Benedict. It is out of print, but probably can be found used at
AbeBooks: New & Used Books, Textbooks, Rare & Out of Print Books or Amazon.
By the way, vegaspilgrim, I know what you mean by the contrast. I've spent a lot of time in and around both Silverton and Gunnison/Crested Butte over the years. Lived in Gunnison for several.
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05-22-2008, 07:22 PM
). But given that, I'm starting to love Denver's weather more and more. I like the fact that most days are not perfectly sunny with no clouds in the sky, like Arizona, but rather are partly cloudy with beautiful puffy cumulous clouds floating across the sky in an ever changing mix. Just watching the skies in Denver, or anywhere on the eastern plains can be quite amazing.
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