The seasonal optical properties of leaves from two deciduous tree species and three evergreen tree species were measured by the use of a Shimadzu UV-2100spectrophotometer with the integrating sphere in the visible region, from summer to the autumn coloration period. In addition, quantitative changes of leaf pigments (chlorophyll, carotenoids, anthocyanin) were also investigated. The striking similarity of the absorption spectrum of the original acetone extract of green leaves from five tree species suggested similarity of the concentration ratio of chlorophyll to carotenoids within the higher plant species. The optical properties of the green leaf showed absorptance around680nm caused by chlorophyll, and between400nm and500nm caused by both chlorophyll and carotenoids. During the autumn coloration period, the leaf optical properties of the deciduous tree species changed. Yellow coloration was due to the rapid decomposition of chlorophyll and the decrease of total carotenoid content. The optical property of the yellow leaf showed absorptance ranges only between400nm and 500nm caused by remaining carotenoids. The optical properties of thered leaf showed absorptance ranges between400and500nm caused by remaining carotenoids, and again between500and580nm caused by the appearance of newly formed red pigment, anthocyanin. The autumn coloration of deciduous tree leaves, or changes of spectral reflectance of tree leaves, was caused by a general physiological process. Hence, forest type classification using remote sensing data would be possible to observethe change in the visible bands in the autumncoloration period.

View full abstract