Douglas L. Airhart & Guy Zimmerman III
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Protecting Trees- What will damage trees? Types of Root Damage: If you drive over the root zone when the soil is wet you will leave ruts. This means you have squeezed out the air, which will cause roots to suffocate. This can damage the tree. If you must drive over the root zone, do it when the soil is very dry, or when the soil is frozen. Or, you may put down a 12- to 14-inch thick layer of mulch over the driving area, which will cushion the root zone and prevent some compaction. One additional consideration might be to put down a metal tire track system to spread the weight of the wheels. Other options are available to protect roots from compaction. Contact a certified arborist for this information. If you install an irrigation system and dig trenches beside tree trunks or anywhere within the drip line, you are cutting through tree roots and damaging the trees. A trench that is installed adjacent to a trunk will cut off approximately 40% of the tree roots (Figure 9-4a), and also make the tree more likely to blow over in high winds because the roots are not present to hold it in the ground on the trench side. Any trenches should be dug outside of the drip line of trees. If you must install pipes, the best route is to trench directly toward the tree trunk, but tunnel under the tree trunk. In this fashion, you will not sever many roots. Another alternative to trenching alongside of a tree is to trench just one-third into the drip line from either side (Figure 9-4b), then tunnel under the middle of drip line to connect the trenches.
If tree roots are exposed on the surface under the tree canopy, and your lawn mower is slicing the tops of the roots, you are damaging the root system. This will allow decay and disease organisms into the root and up into the trunk. You can apply a 3- to 4-inch layer of wood chip or pine bark mulch over the exposed roots to prevent slicing them with the mower. Some grass does not grow well under trees, especially Kentucky 31 fescue. Pick grasses that do well in the shade, such as fine fescue, some turf-type fescue grasses, or bluegrass. If you are building a house and digging a basement, do not spread out the extra soil on or around the tree root zone. Moving the soil onto the root zone will compact the underlying soil. This extra soil also will tend to be compacted, and the new soil layer will prevent air from penetrating to the roots. Use the soil in your flower or vegetable garden, instead. Or build a berm along your property frontage and landscape it to decrease street noise into your yard. Example: Mature Hickory - Video Vignette (See it live!) When we first inspected this hickory, we could not see a trunk flare. The trunk sides jutted straight into the soil. Apparently, soil from digging a residential basement was spread out over the property below the house, and was piled around the trunk a few years ago. It took three turns around the tree with a shovel to find the base of the trunk and then a hand trowel was carefully used to excavate the soil and expose the trunk flare, which was about six inches below the grade. The outer bark was about three-fourths of an inch thick and had rotted away. The inner bark was damp and turning soft. It would not have been too many years before the entire bark would have been rotted and the tree would begin to decline. By the time the property owner noticed the decline and called an arborist for assistance, it would have been too late to rectify the situation. Changing the grade of the soil in root zones to improve water drainage can damage trees. If raising the grade, the new soil will be compacted and will cover the existing roots, possibly smothering them. If lowering the grade, many roots may be damaged and cause severe water stress. Specific construction techniques are available for protecting tree root zones from raising the grade. Contact a certified arborist for this information. Example: Dead Tree in a Tree Well - Video Vignette (See it live!) Grading your property to install a driveway can excavate the top layer of roots. Keep the new pavement away from the drip-line, or even farther out. If you must build a driveway over a tree root zone, add layers of gravel and raise the drive rather than excavating the driveway and tearing up tree roots. Types of Stem Damage If you are building near trees, heavy equipment will compact the root zone, but usually the damage you see is large scrapes and wounds on the sides of trunks. If you protect the root zone of the tree, you will also prevent damage to the trunks and most of the branches. If you must have equipment near the tree trunks, build a sturdy fence away from the trunk and keep equipment from coming near to it. Once again, be sure to protect the root zone from compaction. If heavy equipment is working near trees, they will be likely to scrape big chunks out of the bark, or to break or scrape the lower branches. Protecting the root zone from damage will also protect the trunk (see above). You also may build a suitable fence to protect the trunk. Some lower branches may need to be removed to allow clearance for the equipment. Small flexible branches may be able to be tied back out of the way temporarily. Storing top soils (or excavation soil) from your yard next to and up onto tree trunks will damage the tree. The root zone will be compacted just by moving the soil to the area. The trunk may be seriously wounded while putting the extra topsoil there, but more likely will be damaged when the topsoil is removed while re-spreading it onto your yard. Select a site removed from trees for storing the topsoil, or build a barrier fence at least eight feet out from the trunk. If you must remove an existing tree near the trunk of another tree, do not pull it or dig it out with heavy equipment. The equipment may impact adjacent trunks or otherwise damage the remaining tree stems and branches. Doing so also may compact the root zone. Just cut down the trees to be removed and then cut the stump off at soil level or use a stump grinder to remove it. Types of Branch Damage: Branches often suffer more damage than trunks because of heavy equipment being raised and lowered or from turning around. Most of the tree branches will be protected from damage if construction is restricted from the root zone (as discussed above).
However, selective removal of lower branches can save them from being smashed or broken by any heavy equipment that, for one reason or another, must work around the trees, under the canopy, or within the root zone. Your certified arborist can perform this work on site if the heavy equipment operator will cooperate. It is recommended that branches overhanging driveways should be removed to allow guests and emergency vehicles to enter without hitting them. Not all trees will respond from incorrect pruning. Contact a certified arborist to correctly remove the branches at the collar, not with flush cuts. | ... |
Purpose Right Tree / Right Place Selecting Trees Transplanting Trees Mulching & Staking Summary Diagram Pruning Trees Topping Hurts! Protecting Trees Tree Root Myths Pine Bark Beetles Live Christmas Trees Glossary List of Figures List of Video Vignettes Related Links Bibliography
TLCforTrees.info is maintained by: Douglas Airhart, Ph.D. Certified Arborist & Jeff Plant, Ph.D, Last Updated on: 07/11/03 |
