Thinnings and light conditions in a sugi (Cryptomeria japonica) plantation

概要

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The changes in relative light-intensities on the forest floor after thinning were examined under diffused-light conditions in relationship to the stand characteristics. 1) A method was developed for estimating the ratio of light interception by the trunks under the tree crowns. The light-extinction coefficients of the trunks fell within a range of 0.2 to 0.3. 2) Calculations were made of relative light-intensities on the forest floor intercepted only by the canopy, RCfloor. RCfloor was proportional to the ratio of the crown gap created by thinning to the plot area, Rgap. 3) RCfloor values against the total surface area of all components forming the tree crowns A (ha ha-1) were distributed within a range between two curves of 0.1 and 0.15 of the light-extinction coefficient. The curve came close to 0.15 after thinning. 4) Rsurface was defined as the mean relative light-intensity on surfaces of all components forming the tree crowns. The increase of Rsurface after thinning was about 30%. Rsurface increased exponentially with a decrease of A. The relationship between Rsurfaco and A was considered to be useful in evaluating the thinning effects on light conditions.
日本森林学会の論文