Crown base height
n. The lowest height above the ground on an individual tree above which there is sufficient canopy fuel to propagate fire vertically.
Crown base height is a property of an individual tree, not of a plot, stand, or group of trees (see Canopy base height).
The meaning of crown base height depends on context. In the wildland fire context, crown base height is an effective value that incorporates all available fuel, including ladder fuel such as dead needles, needle drape, and lichen or moss, similar to the stand-level canopy base height.
In a silvicultural sense, crown base height is simply the height on the bole representing the bottom of the live crown, with the bottom of the live crown defined in various ways.
The two contexts differ as follows: the fire context stresses the vertical position of available canopy fuel, whereas the silviculture context focuses on compacted crowns and the insertion point where the branch meets the stem. Crown base height in the fire context is nearly always lower than in the silviculture context.