Converting Tree Diameter Measured at Root Collar to Diameter at Breast Height

Abstract

Pinyon pine (Pinus edulis), Utah juniper (Junipers osteosperma), and Gambel oak (Quercus garnbelii) are dryland tree species often measured for diameter at the root collar (drc) near groundline (Figure 1). This measurement point is below most main stem branching typical of dryland species. The drc measurement standard has worked well for field inventory but presents a problem when results are compared to diameter data of trees measured at breast height dbh (1.37 m above groundline). Basal area calculation and other stand diameter comparisons, for example, are compli-