Here is a list of some of the more common problems that I see:
1) Overwatering - too much water displaces oxygen in the soil around the roots and the tree suffocates. This is typically a problem during Summer when owners overreact to the arrival of hot weather. It's also a fact that most homeowners apply twice as much water as is necessary for they landscape to flourish.
2) Soil compaction - This results from heavy equipment rolling over the root zone during construction. This is most common where new homes are being built on existing lots or where major additions are made to a home. The effect is the same as overwatering in that the soil loses its oxygen and the tree slowly suffocates. Unfortunately, this results in a slow death occuring about two or three years after construction and thus death is not always attributed to the construction. Always keep an eye on the tree canopy to notice stress in the tree. This problem, when combined with overwatering, accelerates the death of the tree.
3) Weed-n-Feed - Application of fertilizers containing weed killer (a broad-leaf herbicide) to the root zone of trees and shrubs can damage roots and stunt the growth of trees for years to come. This is often characterized by deformed new leaf growth during the growing season. Although usually not fatal to the trees, this problem can have extended negative impact in the growth of the trees. I know this from personal experience.
4) Ivy and vines - Often vines will sprout from the base of a tree and climb the tree to access sunlight. Some common problem vines include, English Ivy, Poison Ivy, Trumpet Vine, Virginia Creeper, Wild grape, Greenbriar, and Smilax. These vine cause a number of issues including promoting insect infestations, decreaseing tree vigor due to canopy coverage, and, in extreme cases, canopy deformity. Vines and ivies should be avoided in trees due to these issues.
5) Grade changes - I have seen numerous situations where additional soil was added on top of the root zone due to either home or landscape construction. Over time, tree feeder roots naturally grow in the top 12 inches of soil due to ideal oxygen and moisture levels. When heavy soil is added (loose mulch does not have the same effect) the tree roots lose oxygen and suffocate. If the grade change is minimal (under 4 inches) then the tree can adjust its root growth before it suffocates. If the change is large than 4 inches, the tree cannot adjust its root growth prior to suffocation and the tree dies. A similar problem is caused by mounding soil up aggainst the tree and covering teh root flare (the base of the tree where the trunk begins to widen to attach to the root system). Covering the root flare with soil can prove fatal to the tree as well.
6) Chemical poisoning - I have seen a couple of instances where painters cleaned ther equipment under a homeowner's tree and caused significant damage. Water-based paints are usually not a problem but any activities requiring chemicals to clean up should be kept outside of the tree "dripline."
I have worked on trees that are at least 100 years old and they all are healthy and have another 100 years in them. The thing they have in common is a protected root zone. So to ensure a healthy tree that will last longer - protect the base!
For ways to keep your trees healthy, contact Heritage Tree Service of Texas to get the best advice for your situation.