Abstract

Chlorophyll concentration is related positively to the point of maximum slope in the reflectance spectra of leaves and this point is termed the red edge. The reflectance spectra of slash pine (Pinus elliottii Engelm.) needles were measured in the field and the chlorophyll concentrations of the same needles were measured in the laboratory. The measurement errors for red edge and chlorophyll concentration were determined to be 2.2 nm (3% of mean) and 0.35 mg g-1 (19% of mean), respectively. The red edge--chlorophyll concentration relationship was strong (r2 = 0.82, n = 152). A red edge--chlorophyll concentration relationship for n = 100 was used with red edge measurements to estimate chlorophyll concentration with an rms error of 0.31 mg g-1 (17% of mean, n = 52). The entire red edge--chlorophyll concentration relationship for n = 152 was also used with red edge measurements to estimate the chlorophyll concentration of samples from an earlier experiment with an rms error of 0.47 mg g-1 (30% of mean, n = 38). We conclude that measures of red edge can be used to estimate the chlorophyll concentration of detached needles in the field with an accuracy similar to that obtained by conventional laboratory measurements.