The Predictability of Tree Decay Based on Visual Assessments

Abstract

A field study was conducted to measure the predictability of tree decay based on visual assessments. Predictions made by individual arborists, tree surgeons, and forest ecologists were compared with the actual amounts and distributions of decay in 10 hazardous laurel oaks (Quercus hemisphaerica) that were dissected. The mean deviations of predicted area of decay and predicted loss in strength from actual values were 0.4% and 2%, respectively. The interquartile range for predicted decay area was +12 to -15%; for strength loss it was +8 to -8%. Accuracy of the predictions improved with feedback. The results of this study suggest visual assessment can be a reliable means of predicting the internal extent of decay and hollow in potentially hazardous urban trees.