Forest ecology has long relied on a simple measure-the diameter of the trunk of a tree at breast height (dbh)-as a way to summarise individual tree status and performance. This measurement, with its origins in forestry, is non-destructive and quick to take, requiring no special equipment or extensive training, and this ease of use has led dbh to be widely adopted as the key measure of an individual tree in forest ecology. It is used to quantify and predict individual tree demography (Lines et al., 2010;Ruiz-Benito et al., 2013), as a proxy for tree age (Stephenson et al., 2014), to estimate key properties including leaf area, height, crown shape and biomass (Chave et al., 2014;