Physical stress involves something that restricts root growth, including streets, sidewalks, buildings, construction activities, construction debris in the soil, large boulders, trenching, grade changes, soil compaction, improperly used herbicides, and the roots of other trees. Cultivation of wet soil leads to soil compaction and should be avoided. Animals injure trees in several ways. Animal waste, especially urine, adds toxic compounds to the soil. Animal traffic compacts the soil.
Dogs are particularly destructive when chained to a tree.
People apply a variety of pressures that adversely affect the health of trees. Trees are easily disturbed by construction of buildings and roads, soil compaction, chemicals, air pollution, and improper tree maintenance also fall into this category. In addition to the stresses that come from the direct or indirect actions of people, urban trees also suffer from human inaction. Well meaning people sometimes impede appropriate urban forest management. Education is one way to increase the knowledge of urban forestry and to get people to work together to support it.