Abstract
Crown of forest shrub is a physical factor that affect amenity of the visitors. In this study, interception of the visual field by individual crown of shrub was quantitatively measured through newly defined crown outline, which is based on visual perception theory, followed by discussion about the factors affecting the size of crown side projection area. The visual perception based crown outline was defined as follow, 1) the circles which have fixed diameter (Fixed Diameter Circle, FDC) are circumscribed to the crown projection on the image, 2) the group of the inner arcs is defined as the outline, named AVO (Approximated Visual Outline). The image of the crowns was taken with white cloth behind them. The crown of 28 individuals of Eurya japonica Thunberg were examined with using FDC which have diameter of 30cm. The actual sizes of crown were well estimated from the images. The AVO area was about twice as large as the Profile Projection Outline (PPO) area and about half as Elliptic Outline (EO) area. Each of three crown type show allometric relationship with stem size. The crown depth was increased as the light intensity was increased. The PPO area, which is an index of the amount of mass in a crown, per crown basal area showed positive relationship with light intensity, although PPO area per crown volume have no relationship with light intensity. The fact that the inner structure of the crown of the species do not change along light intensity shows that not structure but size is a primary determinant of the impression of the crown.
