Tree Preservation — Naturally

Berkshires arborist Ron Yaple warns anyone hoping to preserve trees at a building site: Plan for construction, not destruction!

It’s only natural—human nature. We tend to consider maintenance of life only when it breaks, when it hurts or looks bad–when it’s greatly more difficult to intervene with success.

Take your health. It’s our tendency to be reminded of the need for our body’s maintenance when we learn of the illness of someone close to us, or when we’re diagnosed with a disease that might have been prevented with more consistent attention to our body’s needs day-to-day.

The same is true for all life, including your trees. Let’s delve into the common occurrence of irreparable damage to cherished trees caused by landscaping.

Say you buy a beautiful, wooded parcel of land. You’re going to build a house and retain the established, native trees to shade your house and yard — maybe even hang a swing from that low, level branch.

Or you buy a house that suits every need except size—a couple more rooms would be nice. Time for an addition! Or you own a house and you need to excavate for a new septic or water pipe. Or you need 20 tons of topsoil delivered to the back of the house for your garden (yes, that’s just one large truck load.)

Each of these situations can affect the health of your largest landscape feature, your trees. (And I’m aware that referring to them as large features captures a mere thin slice of the whole of trees). Construction damage to trees can exist in many forms. The most common are:

  • soil compaction (healthy soil=healthy trees; compacted soil=low oxygen and retention of toxic gases as roots slowly die);
  • root severance (reducing uptake of water and nutrients);
  • change in drainage patterns (multiple effects based on adaptation);
  • change in surface grade, either cut or fill (root exposure/damage and limiting of the required atmospheric gas exchange/smothering);
  • removal of topsoil (the primary source of nutrients to absorbing roots—90% of absorbing roots are within the top 12” of soil);
  • dramatic changes in the biology of the topsoil (healthy topsoil is loaded with a plethora of beneficial micro and macro organisms);
  • trunk and branch wounding (phloem, primary conductive vessels just under the inner bark, are damaged and killed by wounding);
  • sudden exposure to extra light and heat (the phenomenon known as solar shock); and
  • release of construction-related toxins absorbed by the soil (dripping oils, high pH cement, rinsing of solvents and paints, etc.)
A fresh grade cut that severed roots of the uphill edge trees. Exposed to sunlight, to which they had not adapted, these edge trees will struggle. Plantings that are planned to ‘soften’ this edge could sever more roots of existing trees. Hand planting is recommended. The installation of an irrigation system adds further risk of root damage. Photo: Ron Yaple

Often these assaults cause older trees to enter what arborists know as a decline spiral, the downward movement from full health to death. It begins with stresses, both biotic and abiotic, those caused by biological factors and those caused by outward factors. It is in the abiotic arena that humans play a part in this decline spiral.

Decline disease spiral (Reprinted with permission from Tree Disese Concepts by Paul D. Manion, c. 1991, Prentice-Hall Inc., Englewood Cliffs, N.J.)

In small doses, trees can respond to and tolerate stresses of all kinds. In larger doses, trees mobilize and expend their reserves, reserves they’ve manufactured through photosynthesis, utilized in part to maintain their infrastructure. The starchy excesses are stored in their buds, twigs, and roots in preparation for minor and moderate stresses. Once these reserves are mobilized and depleted, trees become vulnerable to secondary pathogens that have evolved to take advantage of this weakened condition.

The low edge of a planned house wall showing the severance of roots of ‘keeper’ trees and the green drainage pipe that will direct water to a singular location at the base of trees not adapted to this condition. Photo: Ron Yaple
Another angle of the same site showing the dramatic change of grade upslope from trees they hope to retain. Severed roots are more visible at this angle. Photo: Ron Yaple

So—blah, blah, blah — what steps are pertinent?

  • Early involvement of an arborist in tree and site assessment—best connected to the planning of your project beginning with land clearing, house siting, project infrastructure planning including landscape plantings and hardscape (walls, drainage features, irrigation lines, outdoor recreation features, etc.);
  • Defining the trees to be protected or removed;
  • Defining and fencing of tree protection zones;
  • Clarifying the importance of the trees to all site workers and their associates (truck deliveries, parking, etc.);
  • Preparation of the trees in advance of damage;
  • Mitigation of damage when it cannot be avoided; and
  • Follow up care

Let’s define arborist: one knowledgeable in the art, science, and business of establishing, caring for, and removing of woody plants (vines, shrubs, and trees) in the human landscape — from planting to removal, from soil to sky. For better or worse, there is a mish-mash of oversight of the qualifications of arborists. It varies by state and country.

The bare minimum qualifications: either extensive experience working with a licensed or certified arborist or a Massachusetts or New York Certified Arborist or Connecticut Licensed Arborist. Connecticut requires licensing for arborists performing commercial tree work within the state.

More extensive qualifications include:

  • Board Certified Master Arborist (BCMA),
  • Certified Tree Safety Professional (CTSP),
  • State Pesticide Licensing,
  • Tree Risk Assessment Qualification (TRAQ) and
  • Registered Consulting Arborist (RCA).

Each of these levels requires verification of continuing education. Arboriculture is evolving rapidly with changes in research, technology, equipment, and laws affecting our management of trees. Recommendations for new procedures are coming at a break-neck pace.

Why add another layer of oversight? Won’t my house architect, landscape architect, general contractor, foundation contractor, carpenter, plumber, excavator, mason, electrician, heating-ventilation-air conditioning contractor, roofer, and landscaper understand the basic requirements of trees and treat them with care? And the answer is……probably not.

So what’s the big deal? What’s there to know? A lot.

Live crown ratio, critical root radius, root-trunk-leaf function, treatments, soils, cultural requirements, and effective mitigation of construction impacts on health, and on and on.

In conclusion the take-aways are:

  • The most common starting point on the decline spiral involves the soil and roots around established trees.
  • The decline spiral can be interrupted, but often with expensive, unpredictable results.
  • Decline can be slow and may go on for years, with outward signs and symptoms very subtle at first. Rarely do trees decline suddenly—they tap their reserves first. As a case in point: we keep flowers “alive” for days in water—with no roots!
  • It will likely cost more up front, but vastly less in the long run. The return on investment is high!

Start your project with an arborist on your team—you’ll be making a vital difference in the aesthetic and financial value of your property! Construction, not destruction!