If you wish to maintain the health and structural integrity of your trees during construction, be prepared to be persistent and watchful while work is carried out. Understand that some of the symptoms of construction damage can develop slowly, over several years. Your best efforts now can prevent years of remediation.
Trees can be damaged in a number of ways during construction. It is important to understand how your trees may be damaged in order to prevent it.
Physical Injury to Trunk and Crown: Construction equipment can harm the trunk and crown by breaking branches, tearing the bark, and wounding the trunk.
Cutting of Roots: The roots of a mature tree typically grow away from the tree a distance of one to three times the spread of the branches. In addition, 90 percent of the roots that absorb water and minerals are contained within the top 12 inches of soil. As a result, digging and trenching near trees can result in severed roots. Severing one major root can cause the loss of 15 to 25 percent of the root system.
Soil Compaction: Soil needs to be porous, meaning it needs to have space for air and water in order for roots to grow and develop. Soil compaction, caused by running heavy equipment over the soil and human traffic, can greatly reduce the pore space, which in turn reduces the amount of air and water available to the roots, both of which are necessary for tree health.
Smothering Roots by Adding Soil: As mentioned, most of the absorbing roots are within the top few inches of soil. This is because this is the best place for the roots to get the air, water, and nutrients that they need. As a result, adding even a few inches of soil over the existing soil can effectively smother the roots, leading to the decline and possible death of the tree.
Exposure to the Elements: Trees and surrounding plants do not exist in isolation. When a tree, or part of a tree is removed, it can expose parts of other trees or plants surrounding it to sunlight and wind. Too much sunlight may cause sunscald on the trunks and branches of trees with thin bark. Greater exposure to wind can make weaker trees more susceptible to breakage under heavy winds or ice.
Get an arborist involved early in the planning stages of your construction project. Inform your arborist of any proposed grade changes, plans for trenching, and proposed entrance/exit routes for heavy machinery.
Require subcontractors to erect barriers around those trees you wish to preserve. Barriers should be substantial enough to help prevent physical damage to the trunk of the tree or low limbs. They should also be placed as far out from the trunk as possible in order to protect the tree's root zone from compaction by heavy equipment. Build penalties or fines for violating these barriers into your written specifications.
One of the most beneficial things you can do to prevent soil compaction is to spread a thick (6 to 12 inches) layer of mulch over the root zones of your trees. This helps to disperse the weight of heavy equipment. Remember that this quantity of mulch can only be left in place as a temporary measure and will need to be dispersed as soon as possible after work in that area is complete or it will smother the roots of the tree.
If you're planning on landscaping your property, make sure that you carefully plan and communicate with your landscapers as well. Installing irrigation systems and rototilling planting beds can damage the root systems. It would be a pity if you avoided damage to your trees during construction only to have them harmed during landscaping.
If you need any incentive to plan for the preservation of your trees, remember that they have both aesthetic as well as monetary value: a potential 15-20% added value to your home, savings in energy use, and let's not forget the eternal appeal of a tire swing.
Sometimes trees experience damage even when the greatest precautions are taken. It is important to evaluate the condition of all remaining trees on your property once construction is complete. Consult with an arborist about necessary maintenance and monitoring needs.
If your trees are damaged due to construction, do not despair. Many times damaged trees can be saved, but it requires immediate action. The trees may need watering, mulching, bracing, or pruning. An arborist will be able to assess the damage and provide the appropriate treatment, repair and follow up care.
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