A
treefall gap is a distinguishable hole in a
forest with vertical sides extending through all levels down to an average height of two meters above ground. These holes occur as result of a falling tree or large limb. The
ecologist who developed this definition used two meters because believed that "a regrowth height of 2 m was sufficient" for a gap to be considered closed, but not all scientists agreed. For example, Runkle believed that regrowth should be 10–20 meters above the ground. Alternatively, a treefall gap as "the smallest gap [that must] be readily distinguishable amid the complexity of forest structure."