Assessing the Likelihood of Failure Due to Stem Decay Using Different Assessment Techniques

Arborists commonly investigate the extent of stem decay to assess likelihood failure when conducting tree risk assessments. Studies have shown that: (i) arborists can sometimes judge internal based on external signs; (ii) sophisticated tools reliably illustrate decay; and (iii) assessing components be highly subjective. We recruited 18 experienced assessors who held International Society Arboriculture’s Tree Risk Assessment Qualification (TRAQ) due after each five consecutive assessments 30 individuals 2 genera. The assessment techniques, in stepwise order, were: (1) observing visually, (2) sounding trunk with a mallet, (3) viewing scaled diagram cross-section that revealed sound decayed wood ascertained from resistance drilling, (4) sonic electrical tomograms, (5) consulting peer. For technique, assigned two or more ratings (LoFRs) for at least 83% trees, which were proportionally greatest viewed tomograms; proportions did not differ among other four techniques. Covariates influenced distribution LoFRs included percent was decayed, assessors’ experience using drilling devices tomography regular practice. Practitioners should aware disagreement exists even arborists.