Comparing Formulae that Assess Strength Loss Due to Decay in Trees

Abstract

Hazard trees are a concern for anyone who manages trees in a landscape setting, including arborists, urban foresters, and grounds managers. Through research, experience, observation, and common sense, arborists and urban foresters have identified many risk factors that predispose trees to failure. They have also developed thresholds to help determine the degree of hazard and whether a tree is in imminent danger of failing or needs annual (or more frequent) inspections. Two critical factors are involved in strength loss assessment in tree stems with defects. First, it is important to know how much strength is lost due to a defect such as a hollow or cavity. Second, the load required to cause failure needs to be considered since the wood of some trees is inherently stronger than others. Research currently underway at the University of Massachusetts, U.S., intends to test the strength loss due to decay in tree stems. Eventually, once the methodology has been refined, other tree structural defects will also be tested. A need for such research exists because hazard trees pose an important liability issue and because relatively little quantitative testing has been done to establish thresholds to classify trees as hazardous.