Spectral response of architecturally different wheat canopies
1986
Jackson, R.D. | Pinter, P.J. Jr
The spectral response of two architecturally different spring wheat canopies having similar single leaf reflectance, green leaf area index (GLAI), and total dry phytomass, was measured throughout a growing season. Experimental results and supporting model calculations showed that the more planophile canopy had a higher spectral reflectance (measured at nadir) than the erectophile canopy. During the period of peak GLAI, the ratio of near-infrared to red reflectances (IR/red) for the erectophile canopy was about 30% higher than for the planophile canopy. The perpendicular vegetation index (PVI), however, was about 30% higher for the planophile canopy than for the erectophile canopy. When ground measured reflectances were transformed to radiances exiting the top of either a clear or a turbid atmosphere, the differences between the erectophile and the planophile canopies remained for the PVI but were obscured for the IR/red ratio. The results demonstrate the importance of architectural effects on the spectral response of canopies, and the interpretation of that response for estimating GLAI and dry phytomass by use of vegetation indices.
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