Tree heights at the northern edge of their range   Lee Frelich
  Jun 06, 2004 10:43 PDT 


After watching mulberry and catalpa trees in Minneapolis and red maples and
red oaks in the Boundary Waters of northern Minnesota for more than decade,
I am beginning to understand how extreme cold limits tree heights to a
heights much less than the potential for the soils conditions.

This last winter we had an extreme cold spell, and most mulberries and
catalpas in Minneapolis this spring have lost 5-10 feet in height due to
dieback. This seems to happen every 5 years or so.

I wonder if most trees routinely lose a small amount of height quite often
due to dieback from cold in the northern edge of their range, thus
contributing to the pattern of shorter heights with increasing latitude.

Next Saturday I will check some of the red maples and red oaks at Hegman
Lake in northern MN, where it was down to -50 last January. It will be
interesting if they have died back again like they did after the cold
winter of 1995.

RE: Tree heights at the northern edge of their range   Gary A. Beluzo
  Jun 06, 2004 16:20 PDT 


So you are hypothesizing that the shorter overall height gain of the red
maples, red oaks, and mulberries results more from natural "pruning"
rather than altered physiology due to the cold? That is really
interesting Lee, I look forward to further posts on this topic.


Gary A. Beluzo
Professor of Environmental Science
Holyoke Community College
RE: Tree heights at the northern edge of their range   Lee E. Frelich
  Jun 07, 2004 06:01 PDT 


Yes, for some species pruning by freezing of the upper crown appears to
limit height. For other species, and perhaps for these same species further
south, there is probably still a height limitation caused by length of
growing season.