Kodani, E, Awaya, Y, Tanaka, K, Matsumura, N (2002). "Seasonal patterns of canopy structure, biochemistry and spectral reflectance in a broad-leaved deciduous Fagus crenata canopy". FOREST ECOLOGY AND MANAGEMENT, 167(3-Jan), 233-249.
The reflectance of a deciduous forest varies from spring to autumn owing to phenological or seasonal changes in the biophysical or biochemical attributes of the canopy. During the growing season in a broad-leaved deciduous stand of Japanese beech (Fagus crenata), we measured the continuous reflectance factor in the visible to near infrared spectrum (380-900 nm) from a tower and measured biophysical and biochemical attributes of the canopy (leaf area index (LAI), fraction of absorbed photosynthetically active radiation (fAPAR), and chlorophyll content. We analyzed the seasonal variations in the reflectance factor with respect to the seasonal variations in the biophysical or biochemical attributes of the canopy. We simulated the four bands of the moderate resolution imaging spectrometer (MODIS), band 3 (459-479 nm, blue), band 4 (545-565 nm, green), band 1 (620-670 mu, red), band 2 (841-876 nm, near infrared or NIR) and calculated the normalized difference vegetation index (NDVI) by averaging the continuous reflectance factor (380-900 nm) over the spectral range of each band. During the growing season, canopy chlorophyll content had the strongest linear correlation with the red band, LAI had a strong linear correlation with the NIR band, and LAI and fAPAR had the strongest linear correlations with the NDVI. The NDVI had strong linear correlations with the biophysical or biochemical attributes of the entire canopy during the growing season. We analyzed the correlations between narrow bands (380-900 nm, 5 nm band width) and the canopy attributes and found that, during the growing season, LAI had the highest linear correlation with the wavelengths between 750 and 900 nm (NIR), canopy chlorophyll content had the highest linear correlation with the wavelengths between 600 and 640 nm (red), and WAR had the highest linear correlation with the wavelengths between 660 and 680 nm. The red edge (the position of maximum slope in the 680-750 nm region) was linearly correlated with LAI and canopy chlorophyll content. HSI conversion from three visible bands allowed us to detect the turning point of canopy attributes in time series analysis. The canopy attributes changed quickly in the seasons of flushing and yellow coloring. To detect the processes and the turning points of the canopy phenology in a deciduous forest, it was necessary to measure reflectance at least once a week, especially in the flushing season. (C) 2002 Elsevier Science B.V. All rights reserved.