Paul Smiths, NY, Feb 21, 2013 — Martha Foley and Dr. Curt Stager talk about the timberline, the usually abrupt termination of forest growth above a certain altitude. While it results from a combination of unfavorable factors, the final straw seems to be the length of time free of hard frost. When the growing season is too short to overcome damage from the harsh climate, the trees die out.  Go to full article