Patterns of tree shape and position In northeastern forests, the spreading branches of hardwood trees like maple, birch, and ash make them much more vulnerable to injury than softwood trees such as spruce, fir, and hemlock. Tree crowns at the edge of openings, in recently thinned stands, or those that are exposed above the adjacent forest canopy can be hit especially hard. Wood discoloration and decay are the largest sources of lost economic value of hardwood trees. Discoloration and decay are processes initiated by wounding and involve the injured tree, microorganisms, and the environment. Any wound or break that exposes wood causes a defensive reaction in the tree and provides an opportunity for infection by microorganisms.
Trees resist the spread of injury and infection through the process of compartmentalization.
The details of compartmentalization vary among tree species. In all wounded trees, effective compartmentalization leads to relatively little loss of function and small amounts of discolored and decaying wood. Broken branches are the most common form of storm-related injury. Branches that are broken high in the tree crown are not likely to initiate discoloration and decay in the main stem. Discoloration that does spread into the bole from broken branches will tend to be in the central core of the tree, the least valuable portion for products.