How Construction Can Damage Trees
Damage to Roots
Where are the Roots?
The most common types of injury to trees that occur during property improvements are related to root cutting or damage. Tree roots extend farther out than people realize, and the majority are located within the upper 24 inches of soil. The thickest roots are found close to the trunk, and taper and branch into ropey roots. These ropey roots taper and branch into an intricate system of fine fibrous roots, which are connected to an even finer system of fungal filaments. This vast below-ground network is tasked with absorbing water and nutrients, as well as anchoring the tree in the ground, storage, and communication.
Damage from Excavation
Any type of excavation will impact adjacent trees by severing roots and thus cutting off the attached network. Severing larger roots, or trenching across the root plate, destroys large networks. Even work that appears to be far from a tree (like on the far side of the yard), will impact the fibrous root system where excavation is taking place. Placing impervious surface over the ground, or installing below ground structures, such as a pool, or basement wall, will remove rooting area permanently from a site.
Damage from Fill
Adding fill can smother roots, making it difficult for them to access air and water. The roots and other soil life need time to colonize the new upper layers of soil.
Changes to Drainage and Available Water
Changes to the hydrology of the site, caused for instance by new septic fields, changes to grade, and drainage systems, can also cause big changes in available water for trees. Trees can die from lack of water or disease if their water supply dries up or gets much wetter than they are used to.
Soil Compaction and Contamination
In addition, compaction of soil, or contamination of soil with wash-water, paint, fuel, or other chemicals used in the building process, can cause damage to the rooting environment that can last many years. Tree protection fencing creates a barrier to protect as many roots as possible from this damage. Potential causes may include traveling vehicles, equipment storage, and washing out concrete.
Injury from the impact of vehicles or equipment can occur to the root crown, trunk, and lower branches of a tree. The bark protects a tree – creating a skin-like barrier from disease-causing organisms. The stem tissues are in charge of supporting the weight of the plant, and conducting the flow of water, sugars, and other important compounds throughout the tree. When the bark and wood is injured, the structure and health of the tree is compromised.