[at-l] Treeline in Vermont?

[The Weathercarrot]

<<  Can any of you sages explain why treeline up north occurs at lower 
elevations, say, 4000 in Vermont?  Is this just an eastern phenomenon, or is 
it the same in the very northern Rockies too? >>

The primary determining factor for the altitude of treeline is temperature. 
But it's not quite as simple as that.  It has more to do with the length of 
growing season, soil temperature, wind (or angle of slope), and as the link 
below suggests for the northeastern US ranges, the average positioning of 
the winter cloud base, which determines where the most rime ice will 
accumulate.

http://www.earthsky.org/earthcare/shows.php?&date=20021201

In  the western US, the combination of annual temperature distribution, 
precipitation distribution, wind, and icing create very different treeline 
characteristics. Instead of progressively denser krumholtz, such as in 
northern New England, the forests tend to thin out into widely spaced 
clusters or individual trees.

A few more links:

http://www.connix.com/~harry/treeline.htm

http://www.forest.sr.unh.edu/richardson/3Met.pdf

http://geography.berkeley.edu/programcourses/CoursePagesFA2004/geog148/Lectures/Lecture08/Daubenmire.html