My scientist connection confirms that the most likely reason those trees fell over was due to "shallow footing".   When root systems are shallow, rather than deep, soggy weather, especially followed by wind, can easily tip the trees.  My own guess is that the melting snow loosened the soil under the trees, but the really fierce, recent winds of a few weeks ago, rather than the snow itself, most likely brought these trees down.  

Also, it is important to note that the species of evergreen in this area are different than more northerly trees.  For example, there is not supposed to be "jack pine" growing in Maryland.  Instead, the primary pine is Virginia pine.  There is an ecosystem named after the Jack Pine - the Jack Pine Ecosystem - that is very diverse and in some areas is home to birds such as the Kirtland's warbler. It's quite different than the Virginia Pine, although it looks a lot alike.  So while the trees in the north may look similar, they have various adaptations for snow and cold that the southerly species do not. 

Many pines tend to be very shallow rooted.  The Georgia forestry commission's website states "Virginia Pine has a shallow root system and is susceptible to wind throw and damage from ice and snow."  Conversely, most sources say that Jack Pine is fairly shallow rooted but with a large root base (ie, the roots extend a long way out from the trunk, lending stability).  One Canadian research project showed that of the conifers in the study area (I believe in Ontario), only the young Jack Pine had a taproot (thus also lending some stability).  

So I think the puzzle of why the northern trees withstand snows better than here is somewhat one of soil, but also of species.  

While we're on the topic of trees and snow, it might be noted that coniferous trees in truly harsh climates - such as the boreal forests in Siberia - adapt by growing extremely slowly.  In many areas species actually grow in prostrate ("lying down") form.  It is very interesting to see photos of these trees, which have grown in severe weather then responded to the rapid warming which is occuring in Siberia.  Many trees in the region now have a prostrate base combined with a sudden upright growth.  The upright (or arboreal) growth form is a marker of warming temperatures.  The photos show almost a scrubby shrub, topped by an upright tree!  

The slow growth of trees in harsh conditions should allow a larger amount of root area to develop relative to the area of above-ground growth when compared to very rapid growth of trees which occurs in warmer temperatures.  If the tree is putting it's energy into top-growth, the root system will be relatively small.  It's possible that if the North Tract fallen trees were examined, the tree-rings might show that they were fairly young trees that had rapid growth, rather than slow-growing, aged trees.  

And to return to birds, although quite extralimital, it is interesting that the reproduction of some of these harsh-climate boreal conifers (the Siberian Pine) depends in part upon a bird, Nucifraga caryocatactes, locally called the "cedar bird", which forcibly removes seeds from the cone and carries them to new, fertile grounds.  



Joanne

Joanne Howl, DVM

West River, MD. 20778






-----Original Message-----
From: June Tveekrem <>
To: 
Sent: Thu, Mar 11, 2010 9:32 am
Subject: Re: [MDOSPREY] Patuxent North Tract -- Massive Storm Damage


I'm not an expert, but I believe it's the clay soil around here that causes evergreens to uproot and fall over more easily. When the ground gets waterlogged the clay becomes more liquid. Combine the weight of snow on trees, soil not frozen as deeply as in New England, and slippery clay, and you get uprooted trees. The deciduous trees don't accumulate as much snow on their branches due to lack of leaves. I've noticed that branches are more likely to break off of deciduous trees, though, than off of evergreens. 
 
(If there are any soil scientists on this list, they may tell me my explanation is bogus. In that case, I'd like to hear the correct explanation.) 
 
June 
 
-- June Tveekrem 
Columbia, Maryland 
tweekiebird|AT|southernspreadwing.com 
http://SouthernSpreadwing.com 
 
On 3/10/2010 9:22 PM, Laura Appelbaum wrote: 
> what it is about the growth pattern of evergreen trees in regions > where there are frequent snows that differs from those here in Maryland?