BREAKAGE OF HOLLOW TREE STEMS

Stems of trees hollowed by agents such as fungal decay, fire or termit es have reduced strength and increased likelihood of breakage. This ma y pose a serious hazard when hollow trees are growing near public plac es. Previous theoretical studies and field studies of hollow trees, of both hardwood and softwood species, in Europe and America have sugges ted rules to quantify the risk of breakage of hollow trees. These rule s are confirmed and expanded here, using data collected from hollow tr ees of several species of the hardwood genus Eucalyptus in Australia. It is concluded that where the ratio of the minimum wall thickness of a stem hollow to the total radius of the hollow exceeds 0.3-0.35 and a t least one-half of the girth of the tree stem is intact, it is extrem ely unlikely that the stem of the hollow tree will break. These rules appear to apply for a wide range of tree species throughout the world.