Angle distribution of foliage in individual Chamaecyparis obtuse canopies and effect of angle on diffuse light penetration

The vertical distribution of foliage angle and area of three Chamaecyparis obtusa trees was determined by the triangle method, which calculates foliag e geometry using measured coordinates of the leaf "corners", in a 43-year-o ld plantation in central Japan. Vertical distribution patterns of leaf area were different depending on tree size, but the boundary heights, which div ide the canopy into sunlit and shaded parts, were similar in the three samp le trees. The value of the average foliage angle [I(Z)] at a given depth (Z ) from the tip of the stem decreased continually from the upper to lower la yers within the canopy. The vertical patterns of changes in I(Z) were diffe rent among the three trees, but could be expressed by the following allomet ric equation as a function of depth. I (Z)=aZ(b) exp(cZ) where a, b and c are constants. The average foliage angle of C. obtusa depe nded on the position within the canopy and tree size; the value was larger in the sunlit parts of the canopy than in the shaded parts. However, the fo liage angle distribution in the overall canopy fitted an ellipsoidal area d istribution model. The probability of diffuse light penetration through the canopy was calculated using foliage angle and cumulative leaf area paramet ers. The probability was different from that calculated by Beer's Law for l ight extinction, especially in the sunlit part of the canopy. These results suggested that the foliage angle distribution within the canopy is an impo rtant factor in: (1) the estimation of the absorption of diffuse radiation: and (2) evaluation of the amount of absorbed direct radiation in the canop y of this forest.