Roots are responsible for water and mineral nutrient uptake, energy storage, and anchorage. If for any reason tree roots are damaged, tree health will be jeopardized. Because roots work quietly out of sight underground, most people have a poor understanding of this important subterranean network. They usually will not grow where there is no oxygen or where the soil is compacted and hard to penetrate. This need for oxygen explains why a majority of tree roots are located in the top 12 to 18 inches of soil.
Root systems are also extensive.
It is easy to see why any type of soil disturbance near trees can, and usually does cause damage. As trees mature in the landscape they attain a rather delicate balance with their surrounding environment. In fact, trees grow best in an environment of minimal change. Unfortunately, our urban, suburban, and even rural landscapes are places where drastic changes like driveway and sidewalk installation, grade changes, road widening, and utility trenching occur frequently. Such construction activities near trees can cause substantial root injury which may be fatal to established trees.