Many homes are being built in the midst of existing trees to take advantage of the aesthetic and environmental value of forested lots. Wooded properties are often priced higher than those without trees, and people value the opportunity to live among trees. Unfortunately, the processes involved with construction near trees can be fatal. It can be difficult detecting construction damage because trees often go into a decline for several years before dying. It is possible to preserve trees on building sites if caution and forethought are used.
Here are some common types of damage that can occur during home construction, along with possible solutions.
Physical injury to trunk and crown: Equipment can injure the tree by breaking branches, tearing bark, and wounding the trunk. Large wounds can be fatal, and even small wounds can allow decay fungi to enter the tree.
Solution: Erect a construction fence around retained trees as far away from the trunk as possible.
Cutting of roots: Digging and trenching are necessary for underground utilities, which will likely sever a portion of the roots of many trees in the area. The roots of a mature tree extend beyond the canopy, typically growing one to three times the length of the longest branch. The amount of damage to roots depends to some extent on how close to the tree the cut is made. Severing one major root can cause the loss of a large portion of the root system.
Solution: Plan the layout of utilities early and try to avoid their placement near trees.
Soil compaction: Good soil for trees contains a lot of pore space (the spaces between soil particles), which are filled with water and air. The use of heavy equipment compacts the soil, greatly reduces the amount of pore space. This inhibits root growth and decreases oxygen in the soil that is essential to the growth and function of a tree.
Solution: Erecting a barrier to protect trees from physical damage can also serve to prevent soil compaction. Remember that the roots extend out more than you think, so erect the barrier as far from the tree as possible. Try to allow only one access route on and off the property. Good planning may allow this same route to be used as the route for utility wires, water lines, or the driveway.
Smothering roots by adding soil: Ninety-percent of the fine roots that absorb water and minerals are in the upper 6-12 inches of soil, and require space, air and water. Piling soil over the root system will smother it, and it only takes a few inches of it to kill a sensitive, mature tree.
Solution: Plan early and place the house where minimal fill dirt will be needed.
Change in environment: Trees in a forest grow as a community. Drastic removal of neighboring trees will expose the remaining trees to sunlight and wind. High levels of sunlight may cause sunscald on the trunks and branches. A tree adapted to the protection of neighboring trees will be more prone to breaking from wind or ice loading.
Solution: Try to leave groups of trees together to reduce the shock of sudden changes in sunlight and provide some wind protection.
When contracting construction work, include measures to protect trees in writing. The specifications should detail exactly what can and cannot be done to and around the trees. Each sub-contractor needs to be aware of any barriers, limitations, and specified work zones. Posting signs doesn’t hurt. Stay on top of things by visiting the site at least once a day. This vigilance will indicate to workers your wishes are serious. Take photos at every stage of construction so you can prove liability if any contract specification is broken. It will take trees several years to adjust to the injury and environmental changes that occur during construction. Stressed trees are prone to health problems and insect and disease attacks.
Steve Roark is the area forester in Tazewell, Tennessee, for the Tennessee Department of Agriculture, Forestry Division.