Characteristics and Colorimetric Analysis of the Spectral Reflectance of Tree Leaves

Abstract

The seasonal spectral reflectance of tree leaves was measured by the use of a Shimadzu UV-2100 spectrophotometer with the integrating sphere in the region of visible and near infrared, from summer to autumn coloration period. In addition, the spectral reflectance of leaves was analyzed colorimetrically. Following results were obtained.
1) The spectral reflectance of green leaves was found to follow the previously discovered pattern. The spectrum had two major absorption ranges : in the region between 400 and 500 nm and in the region of 680 nm, which are similar to photosynthetic absorption range. Also another characteristic was the reflectance peak in the near infrared region, which was above 750 nm.
During autumn coloration, the properties of the spectral reflectance of leaves changed. The spectral reflectance of the yellow leaf lost its absorption properties in the red region, and showed single absorption characteristics between 400 nm and 500 nm. The spectral reflectance of the red leaf showed absorption ranges between 400 and 500 nm, and again between 500 and 580 nm, the latter being caused by the appearance of newly formed red pigments.
2) The spectral reflectance increased in accordance with the number of layers of leaves. In the spectra of green leaves, the more the layers, the higher they reflected in the near infrared region.
As for yellow and red leaves, the reflectance increased not only in the near infrared region but also in the visible region at the respective wave lengths for yellow and red.
3) Using the CIE (Commission Internationale de I'Eclairage) 1964 supplementary standard colorimetric system, seasonal color change patterns of leaves could be determined.
Results of the present study suggest that these data are useful in the groundwork for further research on vegetation using satellite data.