Visible/near infrared reflectance and chlorophyll content in Eucalyptus leaves

The visible/near infrared reflectance properties of leaves from several Eucalyptus species were studied to determine appropriate indices for remote sensing of chlorophyll content. A scatter correction technique was applied to the reflectance spectra to reduce the additive and multiplicative scattering effects of leaf surface and internal structure. This method gave improved calibrations for the estimation of chlorophyll content. Reflectance near 710nm wavelength showed maximum sensitivity to chlorophyll content. Reflectance near 550nm was a less sensitive indicator of chlorophyll content. Among several reflectance indices tested, the ratio (R850-R710)/(R850-R680) performed best, and is proposed as a new index for the remote estimation of chlorophyll content in higher plants. From the first derivative of reflectance, the ratio D1(754)/D1(704) and the wavelength position of the red edge were best correlated to chlorophyll content. The ratio D2(712)/D2(688) from the second derivative of reflectance was also an equally good indicator of chlorophyll content.