Stem or Trunk Failure:
Trees do not heal wounds and can only grow over old wounds to seal them off. A tree carries every injury it has ever had and the sites of these injuries are structurally weaker than normal solid wood. These weak areas can quickly fail under storm storm conditions leading to tree stem or trunk damage and breakage.
The "Cure": Properly prune by cutting appropriate branches (learn how to prune) before they become larger than 1 inch in diameter. Do not damage the branch collar as it is part of the stem. Do not over-treat tree hollows by removing decayed wood unless it falls away in your hands. Cleaning hollows can lead to further internal damage. In special situations, covering the openings to hollows may allow the tree to grow over the opening. Covering also prevents animals from digging out the hollow and keeps water from running in. In most cases, for small injury, just leave the wound alone.
Severe stem failure can cause the tree's removal depending on a tree species' growth characteristics and its ability to properly re-form in the landscape. Any removal of a tree with stem damage using a chainsaw should be done by an experienced operator.
You need to know that there are two types of tree roots: fine, absorbing roots and woody, structural roots. Both types are important in anchoring a tree. If these roots are constrained, diseased or damaged a tree can lean or fall leading to total tree failure.
The "Cure": Avoid constraining the root systems by boxing in between foundations, sidewalks and pavement. Construction damage, compaction and toxic materials can kill roots and invite diseases - supervise all construction. Remember that as a tree becomes larger, greater stress is put on the roots. Problems associated with root damage and constraints will show up as the tree ages.
A branch is attached to a tree by a small layer of stem wood called the branch collar. Branches are designed to come off at times and a healthy tree will seal off that spot over time. Ice storms or down-bursts that occur can leave the branches unprepared and susceptible to tearing downward along the stem or snapping.
The "Cure": Again, proper pruning minimizes a number of structural problems that occur in association with new wood growth around a pruned branch. Remove or treat pest problems such as branch cankers to minimize potential damage.