What is a definite indicator of tree decay?

A cavity within a tree is a significant indicator of decay because it often forms when the tree's internal structure is compromised by fungal decay, insect activity, or physical damage. When a cavity occurs, it indicates a loss of sound wood and the presence of rotting material inside the tree. This is critical in tree risk assessment, as a cavity can lead to weakened structural integrity, increasing the risk of failure.

Old wounds, while potentially associated with decay, do not always indicate active decay since some trees can compartmentalize and heal over time. Cracks may also suggest structural issues but can occur without decay being present. Response growth patterns, which indicate the tree’s reaction to stress, can provide insights into a tree’s health but do not definitively point to existing decay. Therefore, a cavity serves as a clear and compelling sign of decay in a tree.