Last Friday brought some welcome rain, but some not-so-welcome thunderstorms along with it. 
Here at Pine Mountain, a large and seemingly healthy Hemlock succumbed to the high winds and fell. Fortunately, no one was around these specific trees, but I thought it important to talk about what are called “High Risk” or “Nuisance” Trees. These are trees that at elevated risk for damaging property and/or hurting people.
While an individual plant within a stand of trees or an individual corn stalk within an acre of corn, is protected by the plants around it, it’s important to remember that there are limits to this protection. Additionally, trees at the edge of a forest or even standing alone within a field are much more susceptible to falling.
Unfortunately, this is where humans tend to build homes: at the edge of the forest, near trees. This is not to say that one cannot live near trees. 
How tragic would that be? All that one must do is evaluate the trees around homes and recreational spaces. While it is quite easy to see when a tree or branch is dead, it is difficult to tell when trees are in what’s called a “mortality spiral” because decay can be hidden deep within the tree’s structure. A mortality spiral can take decades to complete, but is generally the result of multiple factors including bad decisions, bad weather, and diseases or pests acting on a tree over time.
The previous picture (click to enlarge) and following guide are a great resources for identifying critical traits for trees at risk and steps one can take to fix certain problems:
Identify and Manage Hazardous Defects in Your Trees
Trees are a great way for those of us in the forested mountains to take breaks from our gardening and enjoy the shade in the summer. Armed with the proper knowledge about trees, it only takes a moment to evaluate what trees in our yards are safe to relax under and which trees need our attention. Trees along our gardens provide us with shade and protect our more fragile plants from harsh winds. Keeping an eye on them and helping them stay healthy is a way to return those favors.
I am over near whitesburg. Your diagram was very interesting and helpful. Another thing that causes trees to fall is a LOT of rain. Shallow rooted trees can wash down off a mountain.
Also, acid rain gradually kills a tree and the roots break off. I don’t know if there’s any signs of it though.
great post Josh. And timely too. We lost a big tree at teh monastery last week in high winds very near the house. The good news is it fell down the mountain. The bad news is broke several smaller trees when it fell.