Why do some trees fall during storms and others don't?

The answers to this question may not be very comforting: The first thing to know is that all trees have the potential to fail at some level of force from wind, snow, ice, either singly or in combination. One main reason is the phenomenon known as “windthrow” which uproots a tree. The tree trunk acts as a lever and so the force applied to the roots and trunk increases with height. Taller trees are more susceptible to "windthrow.” Generally trees tend to uproot more than break off during wind events, although poor structure in the crown will result in limb breakage, splitting and tearing as well.

Wood is a very strong and wonderful structural material, however, wood is not homogeneous or consistently strong at all places in the stem (trunk). Wood decay caused by fungi can weaken wood structure. However, the mere presence of decayed wood or even a hollow does not mean that the tree is more vulnerable to failure. Strength comes from the quality and quantity of wood that is present, not what might have been degraded. An equally big factor in tree falls is bark between two trunks or between branches and the trunk, and wounds from past injuries which make a tree vulnerable when high winds bend its branches or even cause the trunk to sway.

Are some types of trees at more risk than others? Trees most at risk are those whose environment has recently changed (say in the last 5 - 10 years). When trees that are living among other trees, for example, lose physical protection around them and become stand-alones in new housing lots or become the edge trees of an area, they are made more vulnerable to strong weather elements such as wind.

Other risk factors: Large trees growing in shallow soil or in a rocky area and trees that were accustomed to living in a forest.