Why Storm Damage Happens
Trees falling on houses, across roads or taking out power lines are common news headlines after major storms. This gives the misimpression that trees are dangerous. What is often overlooked is that there usually is an underlying reason why trees fall or break.
Underlying Causes that Can Lead to Down or Damaged Trees
Healthy trees can cope quite successfully with the additional loads put on them during storms. So then, why do we see so much damage following, for example, a wind storm? To find an answer to this question we must first understand what causes trees to fall and break. There are several contributing factors including the extent of a defect, tree type (some species are more susceptible than others), age (older trees tend to be more vulnerable), site characteristics (rock ledges, saturated or eroded soils) and wind patterns.
The causes of failure are commonly broken up into non-infectious and infectious.
Poor Tree Structure
During site inspections, we encounter a good number of trees that have poor structure consisting of multiple trunks competing with each other. When this happens, included bark is formed. This situation can be prevented through proper maintenance when the trees are young (also referred to as developmental pruning). Mature trees with this type of defect can often be cabled or braced.
This damage is most frequently the result of some form of soil excavation. In these cases, prevention consists of keeping potentially harmful objects (i.e. construction equipment, vehicles, tools, etc.) a safe distance from the tree roots. A rule of thumb is to stay as far away as the projection of the furthest branch.
Often the result of an injury that lends itself as a breading ground for opportunistic fungi in the tree. Detecting decay is now done using an instrument called a resistograph which can even reveal a decay pocket invisible from the outside.
Anchoring roots can die off while a tree still appears healthy because it is able to send out enough adventitious roots to keep itself supplied with water and minerals. However, the loss of anchoring roots leaves the tree vulnerable. Fortunately, here too, arborists can perform a basal examination to determine if the roots are affected by decay.