Young trees are less able to with stand stress than established trees. Knowing what is abnormal requires that one knows what is normal. An example of this is that is normal for a spruce tree to have no needles in the centre of the tree. If one doesn't know what is normal, compare the tree to others of the same species growing nearby. This will give an opportunity to also determine if the problem is isolated to a single tree or has a larger pattern.
Random damage is often the result of a living factor such as insects and disease.
A regular pattern of damage is usually due to a environmental factor particularly if the damage is apparent over a number of plant species. The third step is a careful examination of the site. Just as detectives look for clues on a body, they also look for clues at the scene of the crime. One must check how a tree has been situated. Things to be noted are the contour of the land, and the structures near the tree.