Tree maximums at high altitude (24) Robert Leverett
June 28, 2009


From a very limited base of experience, I'll do the best to address the questions you raised. My comments won't resolve anything, but hopefully will stimulate further discussion. 
There are unquestionably numerous areas in the San Juans at 2 miles above sea level or more with significant potential for big and/tall trees. The watershed around 10,850-foot Wolf Creek Pass is a certainty. It has already proven itself. The watershed around 10,910-foot Molas Divide just north of Coal Bank Pass is highly likely. I expect Red 11,018-foot Mountain Pass  between Silverton and Ouray holds possibilities. I am curious about 11,361-foot Slumgullion Pass in the eastern San Juans. These passes are all on major roads. There are several other high altitude passes in the san Juans reachable from Forest Service roads. The bottom line is that there is abundant territory to cover that is fairly accessible and then there are thousands of acres if really remote country. I'll never see that country, unless I can reverse the process of aging, but it is comforting to know that the places exist in pristine form.
Now to the second question.  What about areas to the north, particularly  Wyoming? First let me generalize. I believe that the absence or presence of trees in the Rockies reaching 130 feet in height at 2 miles above sea level is tied primarily to four factors: (1) the amount of moisture received during the growing season, (2) the latitude, (3) the amount of high altitude country, and (4) the number of species present capable of reaching into the higher numbers. In the San Juans, the Colorado blue spruce and the Englemann spruce are present at 2 miles above sea level and can reach 130 feet. I'm unsure where the Douglas fir drops out. It certainly can reach well above 130 where present in abundance. Two miles up is above the altitude limit of the ponderosa. I don't think that subalpine fir will make 130 feet. Maybe I'm wrong.  
Let's now consider latitude. Timber line in central Wyoming is between 10,000 and 10,500 feet and lower in northern Wyoming, so there are no trees at 2 miles high by the time you reach northern Wyoming. Farther north, of course the timber line continues to drop, so the entire geographical region can be ruled out. In terms of moisture, the  San Juans receive a ton of winter snow that is translated into a long spring runoff period. The amount of snow here is truly impressive. Wolf Creek Pass holds the Colorado record for the highest annual average snowfall and the greatest single year's total. The pass received an unbelievable 837 inches of snow one year. I've forgotten the year. In terms of averages, it is around 400 inches per year. I've seen higher numbers, but they may be ski resort propaganda. Interestingly, August is the wettest period of the spring and summer season. Traditionally May and Jume are dry, but in most years, the high country continues to feed water to lower elevations via snow melt. Finally, there is the acreage of high altitude country to feed water to lower elevations. It wouldn't be enough for a mountain range to top out at the 2 mile mark. There has to be a lot of territory above 2 miles. In that department, as a mountain range, the San Juans are #1 in the lower 48. 
Now to another question.  The other main species at the pass is subalpine fir. If I had my thinking cap on, I could have probably obtained a record for that species also. I didn't see in limber pine there, a species I often expect to see at those altitudes.
Finally, t he tall spruce at Coal Bank Pass is part of a grove. Large and tall spruce are more typically in groves than isolated trees. The meadow trees I showed photos of were photogenic. So I chose them as subjects.  As in the East, the tall stuff out here grows in the ravines where water and protection is most available.

Jess, I've attached two more photos to hopefully give you a sense of the forest aspect near the pass. There is plenty of 'grove habitat'. The terrain quickly gives way to meadows and above that tundra, of course. But there is no shortage of stands.


P.S. Ed has done an excellent job of identifying high altitude areas in the Rocky Mountain corridor that could break the 130.5-foot record. The spot in southern New Mexico may be the best candidate.

----- Original Message -----
From: "Jess Riddle" <jess.rid>
Sent: Saturday, June 27, 2009 3:40:56 PM GMT -05:00 US/Canada Eastern
Subject: [ENTS] Re: Coal Bank Pass Tree Treasures


I've enjoyed reading your accounts of your western adventures, and
they have me wondering about the conditions that allow the trees to
reach such great heights for the elevation.  That lack of any trees at
comparable sites in Wyoming could largely be a result of Wyoming's
higher latitude, but how does Coal Bank Pass compare to similar sites
in the San Jauns?  From your photos, all the big spruce appear to be
in meadows.  Are there any large spruce in the more forested areas?
Are the large or tall trees restricted to certain topographic
positions?  Do any other tree species occur at the pass?  I'm
completely unfamiliar with forests in that part of the country, but I
think learning about them could help shed light what factors are
locally important for trees becoming large versus what conditions are
universal requirements for trees to approach their maximum dimensions.


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