Diameter at breast height (DBH)
The standard stem diameter measurement taken at a fixed height above ground, the foundation of forest biomass inventories.
DBH is measured at a conventional reference height so that plots measured by different teams remain comparable. It is the single most influential field variable in a biomass estimate, because volume scales steeply with diameter.
Consistency in the measurement rule — height, slope correction, treatment of buttresses, forks and multi-stem trees — matters more than instrument precision. Documented protocol is what allows two campaigns to be pooled.
Frequently asked questions
Why a fixed height?
Because stem taper means diameter varies with height; a standard point makes measurements comparable.
What about trees too small to measure?
They are recorded in a separate regeneration class and accounted with their own allometry.