Question
Yesterday an old tree (at least 20 - 40 years) had about 1/3 of the bark stripped off of one side of the tree about 5 ft high.  The tree splits into two major limbs about 2 ft from the ground.  The side that was damaged appears to be the smaller of the two limbs that split 2ft from the ground.  What are the chances it will survive?  Is there anything I can do to improve the odds?

Answer
It will depend on the species of the tree and the health of the tree before it was damaged. Hardwood trees seem to do better than conifers. And if the foliage was thick and green when it had leaves it is healthy.
The best thing you can do for the tree is to cut any of the loose bark from the wound--this will let the tree heal over the wound faster. Also fertilize the tree.
Here is a good web link that describes the fertilizer to use and the amount.

http://hgic.clemson.edu/factsheets/HGIC1000.htm