Root Tracing
You cannot properly protect tree roots if you don't know where the major roots are located. With the Air Spade I can do that without damaging the tree.
I am often asked to locate tree roots so construction of a building or parking lot can be adapted, if possible, to accommodate the roots. My primary tool is the Air Spade, a air excavation device that is indispensible for low impact (nearly non-invasive) removal of soil over roots.
Figure 1 This photo of a pignut hickory after root tracing with an Air Spade shows a very symetric root distribution.
Drive-through lanes were planned within 10 feet of this hickory tree. Because the root system is neatly symetrical, I determined that the pruning of one root about 9 feet from the trunk would not be a significant loss for the tree. And four years later the tree is doing fine and shows no signs of decline or dieback.
The Publix Project
According to the project design team, the parking lot and major
Figure 2 The 60-inch dbh tree following construction. Even though the parking lot was installed within 12 feet of the tree, there were no major roots on that side of the tree that extended more than 9 feet from the trunk. Hence the parking lot construction had minimal impact on the tree.
driveway in this 5-acre supermarket and bank development had to be placed within 10 to 12 feet of a 60-inch dbh live oak. That distance was just too close for my comfort level. But we decided to trace the roots to determine how many and what size roots would be damaged.
Air Spade excavation (Figure 3) found that most of the major roots were on the side of the tree opposite the planned road and parking lot. After talking with the landowner, I learned that about thirty years ago the tree roots had been pruned or otherwise damaged to accomodate a small spring-fed pond that was the centerpiece of a small local zoo and park.
I used an Air Spade to locate roots and determine how far from the tree the largest lateral roots extended.
The callused, severed root stubs were located about 9 feet from the trunk. Only a few small, approximately 1/2-inch diameter roots grew out of the 6-inch diameter root stubs. The edge of the road and parking lot was to be 12 feet from the tree. So the tree was retained and the work on the parking lot and road proceeded. In Figure 5 below you can see the excavation trench that was made under the road for the drainage pipes. When this trench
Figure 4 Before construction began, the canopy was lifted to allow clearance for heavy equipment, which moved outside the critical root zone that we had established. The critcal root zone on the left side of the tree was only 9 to 10 feet from the trunk. The critcal root zone on the right side of the tree was much larger and extended well beyond the dripline of the tree.
was excavated, no major roots were found protruding into the trench confirming the results of the Air Spade work.
Root tracing is a non-invasive method of determining where major roots are located.
For other aspects of the Publix Project, go to Publix Project on this web site. The excavation for the road and parking lot was done in 2004. Today that tree is still doing fine (Figure 2) and is a significant specimen in the Publix parking lot.
Figure 5 During construction, a trench for the drainage pipe had to be installed right next to the edge of the parking lot about 12 feet from the tree. The trench excavation confirmed my Air Spade analysis that all major roots terminated 9 feet from the tree. No major roots were found protruding into the trench.
