Preventing Tree Loss from Construction

Home Grown  by Keith Reed
Mature tree loss due to land disturbance and/or construction activity is a very common problem in Payne County. The cause/effect case for this problem is a challenge since the time between a tree’s root system being damaged until it starts to show significant decline can be several years.

This is a topic that must be discussed in general terms as each situation is unique and the potential for damage can vary widely based on factors such as species of tree, soil type, overall tree health prior to damage, and even the time of year the damage occurs.

Somewhere along the way, an idea became popular that a tree’s root system is simply an underground representation of what the tree canopy looks like. In other words, the root system is a mirror image of the above ground part of the tree. A popular idea, but completely incorrect.

A better visual representation would be to think of a dinner plate turned upside down with a wine glass on top of it. The globe of the glass represents the canopy of the tree, the stem the tree trunk, and the dinner plate the part of the root system that is most sensitive to disruption. It is this “dinner plate” part of the root system that we should me most concerned about protecting. In real terms, this is about the top 12 to 18 inches of soil extending out two to three times the size of the tree canopy.

Damage can take several forms and may either be direct such as physical removal or severing of roots, or indirect. Examples of indirect damage usually involving reducing air exchange with excessive compaction or complete coverage (such as concrete).

Obviously, it is practically impossible to prevent disturbance to an area this large in the vast majority of landscape situations. However, it is this entire area that should be looked critically before a construction project begins and disturbance in these areas should be minimized as much as possible.

Simple steps to minimize problems include:
  • Having a straightforward discussion with contractors, construction crews to make it very clear that the sensitive areas are to be protected. Once again, the time delay-to-damage is important here. Just because crews may have always used shady areas to store materials, mix mortar, or park construction vehicles without seeing trees die should not be a part of this discussion.
  • Use sturdy construction fencing closing off the entire area. Yellow or orange tape around a tree trunk is woefully inadequate.
  • If trenching in an area cannot be avoided, there are alternatives such as hand trenching to avoid damaging larger roots or using an air spade or even underground boring equipment.

It is also important to note how construction changes can impact the microclimate of a landscape. Examples here include changes in wind movement, sunlight intensity or moisture. These changes are not necessary bad, but once again, this is highly dependent on a variety of factors.

For more information on this or any other horticultural topic, you can contact Keith Reed, the Horticulturist in the Payne County Extension office. Keith can be reached via email at keith.reed@okstate.edu, phone at 405-747-8320, or in person at the Payne County Extension office, located at 315 W. 6th in Stillwater.

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