樹木葉の色彩学的特性に関する研究 (II) : 紅葉期の葉色の変化について

Abstract

京都大学北部構内に植栽された24種の樹木を対象に, 落葉樹・常緑樹の紅葉期の葉色の変位特性を夏期の変位と比較することにより相対的な変位度を検討した。葉色を色彩色差計により計測し, CIE (L* a* b*) 表色系に準拠し, L* (明度), C* (彩度), H°(色相) を分析の軸とした。概して紅葉期に落葉樹は常緑樹に比べ3軸とも紅葉期の変位が大きい。常緑樹は夏期のL*, C* の変位が紅葉期より大きいものが12種中8種に及んだ。また, 紅葉期の葉色の総合的な変位指標として"変位指数"という相対評価値を求めてみた。

Selecting 24 species of trees, which had planted in the northern campus of Kyouto Univ., we analized their leaf colors by using the colorimeter (MINOLTA CR-100) during about four months (the end of July to the beginning of December in 1991). We tried to characterize leaf color changes between deciduous trees and evergreens mainly in red leaves season by L*, C* and H°, that is to say, three axes of CIE1976 (L*, a*, b *) -Color Space. Generally in each axis, color changeable range of desiduous trees are wider than evergreens in red leaves season. But 8 out of 12 species of evergreen trees were wider changeable range in summer season than red leaves season on axes of L* and C*. As a total changeable range index of leaf color in red leaves season, we showed the following formula. T.C.R.-INDEX (TOTAL CHANGEABLE RANGE INDEX) of tree spesies (i)=1/3 {L*i (MAX-MIN)/L*max (MAX-MIN)×100 +C*i (MAX-MIN)/C*max (MAX-MIN)×100 +H°i (MAX-MIN)/H°max (MAX-MIN)×100}