Construction and landscape activities can have a negative impact on existing trees, but the damage is often not visible for several years.
The University of Georgia Center for Urban Agriculture has produced an excellent leaflet that discusses tree protection during construction.
The following suggestions and comments are from the Urban Agriculture Center’s leaflet.
There are five areas of concern for tree health during construction: physical damage, soil cuts, soil fills, soil compaction and chemical damage.
Landscape professionals, arborists and property owners should meet on-site with the building contractor at the inception of the project to set clear and reasonable goals for tree protection. Buildings, walkways and utilities should be sighted, not only for their greatest aesthetic appeal, but also to minimize damage to the existing trees. The building contractor will need to identify the primary access routes, work areas, material storage areas, parking and paint/concrete washout areas.
Other major considerations are soil grading activities that occur in a critical rooting zone, which may change drainage patterns. Clear communication among all parties involved is key to a successful tree save.
Grading equipment hitting the sides of a tree is not good at all. The cambium layer, which transports food and water, is located on the outer circumference of the trunk and is only protected by a thin bark layer. If the cambium layer is damaged, food and water transport will be affected. If a significant amount of the cambium layer is damaged the tree will die.
Soil cuts and fills occur when soil is removed (cut) or added (fill). This includes trenching. Cuts and fills impact the roots ability to exchange oxygen and transport water. Significant root damage is caused with cuts greater than 2 inches in clay soils and 10 inches in sandy soil.
Likewise, fills exceeding 1 inch of clay soils and 8 inches of sandy soil initiate root damage. Root death occurs with the addition of 3 inches of clay soil and 24 inches of sandy soil.
Trenching for utilities may also be damaging to trees. Trenching severs the root system, killing roots from the severed point outward.
Soil compaction is a silent killer of urban trees. Tree decline from soil compaction may take three to seven years to appear. Stockpiled building materials, heavy machinery and excessive foot traffic all damage soil structure.
Chemical damage of trees may occur if equipment and concrete wash out areas are not properly sited.
Note that in many cases every tree can or should be saved. Every site is different. Some may have diseased trees and/or trees which pose a danger.
Developing a plan ahead of time is the key.
Once the desirable trees and construction routes are determined, the tree protection zones and signage for designated equipment wash out areas should be installed.
Orange tree save fencing is commonly used, being easy to remove when it is inconvenient to go around the tree save area.
For more information contact the Dawson County Extension Office at (706) 265-2442.
Clark Beusse is the Dawson County Extension Agent.