Forestry expert witness Russell E. Carlson, RCA, BCMA, Tree Tech Consulting, writes on Guidelines for Protection of Trees on Construction Sites:
To preserve certain mature trees within a construction site some precautions must be taken to assure that neither the trunk, limbs nor root system of the tree are excessively damaged. The root system of a tree is the most vital and the most delicate part of the plant, and the most easily damaged.
The root system extends far from the trunk, often beyond the drip-line of the tree. The fine absorbing roots, those that collect water and nourishment for the tree, are located primarily within the top eight to twelve inches of the soil. (See Figure 1) The roots and the soil in this surface layer must be protected from injury.
Any encroachment, disturbance, or compaction of the soil around the tree will damage or destroy the fine absorbing roots. Injury caused by cutting, crushing, suffocation, poisoning, or moisture stress by inundation or dehydration can result in the death of the tree. Injuries caused during construction projects may not be finally apparent for many years after the completion of the project, but can ultimately kill the tree.
The following guidelines are minimum standards recommended for the preservation of trees. These guidelines should be incorporated in construction contracts, and the details made available to all parties involved with work on the site, including equipment operators. Other guidelines and protective measures may also be appropriate, in addition tho those listed below.