Figure 6: Two gap size accumulation curves measured in the old black spruce
stand using an optical instrument (TRAC) at two zolar zenith angles.
In both cases (a) and (b), teh accumulation of the gap fraction resulting
from gap of various sizes can be separated into two components:
gaps between (F_at) and within (F_as) tree crowns. The portion of the
curve in the l range 10-50 cm is due to branch architecture.