Other Actions that Harm Trees
Figure 1, Photo by Bruce Hagen
Weed 'wackers' (string trimmers), when used carelessly can cause serious injury to the lower trunk or even girdle the entire trunk of a young tree. Partial bark loss as seen here, exposes the tree to wood decay fungi. This a one of the reasons why turf should be kept well away from the base of trees, particularly young ones. Ideally, a tree should have space around its trunk equal to the size of its canopy or beyond.
Any wounding of the bark (the tree's ‘skin') creates an opening in the naturally protective bark layer, exposing the wood to pathogens, or attracting some destructive insect pests. Even carving on trees as seen here is harmful and disfigures the tree as well. See Figure 2.