Friday, August 4, 2000
Tree Talk - surviving construction
If a tree is alive one year after construction did it survive ? Maybe not, construction damage can take a few years to take effect. My home was built in 1985, but I'll be removing 3-4 mature white pines in the next year because they have become hazardous. Their decline is a direct result of construction injuries. Too bad, they're beautiful trees.
Three common construction injuries are bark damage, root loss and soil compaction. Bark damage on a trunk is an entry point for decay that often spreads to the roots. Root loss from excavation in the 30% range makes a tree vulnerable to pests, disease and wind-throw. Soil compaction happens when the ground above the root zone is packed down by construction equipment, pickup trucks, building materials, foot traffic etc. Healthy soil is an amazing 30 to 50% void by volume. Without those pores compacted roots can't get enough air or water. Soil microbial activity is shut down and nutrients made available only through the decay process are no longer available to the tree.
Prevention? Temporary, but sturdy fences are at the top of the list. Work out space requirements that include room for parking and staging material, then fence off the rest before any work has begun. Keep in mind that root systems are big, often twice the diameter of the crown, and also shallow, around one foot deep. Site design should consider the impact of not just foundations and driveways but also underground trenches used for utilities and irrigation systems. Minimize grade changes around trees to a few inches or carefully design for drainage and ventilation. Perform final soil-grading near trees by hand to avoid nicks from Bobcats. Root pruning in advance of the bulldozer/excavator can spare the root system from a lot of unnecessary ripping and tearing; even better if this can be done a year in advance. Stump grinding is preferred over pulling stumps if damage to adjacent trees is a concern.
John Bakewell is a Massachusetts Certified Arborist.
© 2000 The Carlisle Mosquito