Leaf Pigments

The leaf pigment VIs provide a measure of stress-related pigments, which are present in higher concentrations in weakened vegetation. These VIs do not measure chlorophyll, which is measured using the greenness indices.

Anthocyanin Reflectance Index 1 (ARI1)

Anthocyanins are water-soluble pigments abundant in newly forming leaves and those undergoing senescence. Weakening vegetation contains higher concentrations of anthocyanins, so this index is one measure of stressed vegetation. Increases in ARI1 indicate canopy changes in foliage via new growth or death. This index uses reflectance measurements in the visible spectrum to take advantage of the absorption signatures of stress-related pigments.

See Narrowband Definitions for the allowable range of wavelengths.

Use the Radiometric Calibration tool or an atmospheric correction tool to calibrate the imagery to surface reflectance before computing this index. Reflectance values need to be scaled from 0 to 1. Edit the reflectance scale factor field in the ENVI header file (.hdr) as needed to scale the reflectance data from 0 to 1. Or, edit the output reflectance parameter in FLAASH.

Reference: Gitelson, A., M. Merzlyak, and O. Chivkunova. "Optical Properties and Nondestructive Estimation of Anthocyanin Content in Plant Leaves." Photochemistry and Photobiology 71 (2001): 38-45.

Anthocyanin Reflectance Index 2 (ARI2)

This index is a modification to the ARI1 that detects higher concentrations of anthocyanins in vegetation.

It uses reflectance measurements in the visible spectrum to take advantage of the absorption signatures of stress-related pigments. See Narrowband Definitions for the allowable range of wavelengths.

Use the Radiometric Calibration tool or an atmospheric correction tool to calibrate the imagery to surface reflectance before computing this index. Reflectance values need to be scaled from 0 to 1. Edit the reflectance scale factor field in the ENVI header file (.hdr) as needed to scale the reflectance data from 0 to 1. Or, edit the output reflectance parameter in FLAASH.

Reference: Gitelson, A., M. Merzlyak, and O. Chivkunova. "Optical Properties and Nondestructive Estimation of Anthocyanin Content in Plant Leaves." Photochemistry and Photobiology 71 (2001): 38-45.

Carotenoid Reflectance Index 1 (CRI1)

Carotenoids function in light absorption processes in plants, as well as in protecting plants from the harmful effects of too much light. Weakening vegetation contains higher concentrations of carotenoids, so this index is one measure of stressed vegetation. Higher CRI1 values mean greater carotenoid concentration relative to chlorophyll.

The value of this index ranges from 0 to more than 15. The common range for green vegetation is 1 to 12. This index uses reflectance measurements in the visible spectrum to take advantage of the absorption signatures of stress-related pigments. See Narrowband Definitions for the allowable range of wavelengths.

Use the Radiometric Calibration tool or an atmospheric correction tool to calibrate the imagery to surface reflectance before computing this index. Reflectance values need to be scaled from 0 to 1. Edit the reflectance scale factor field in the ENVI header file (.hdr) as needed to scale the reflectance data from 0 to 1. Or, edit the output reflectance parameter in FLAASH.

Reference: Gitelson, A., et al. "Assessing Carotenoid Content in Plant Leaves with Reflectance Spectroscopy." Photochemistry and Photobiology 75 (2002): 272-281.

Carotenoid Reflectance Index 2 (CRI2)

This index is a modification to CRI1 that provides better results in areas of high carotenoid concentration. Higher CRI2 values mean greater carotenoid concentration relative to chlorophyll.

The value of this index ranges from 0 to more than 15. The common range for green vegetation is 1 to 11. This index uses reflectance measurements in the visible spectrum to take advantage of the absorption signatures of stress-related pigments. Reflectance data should be scaled from 0 to 1. See Narrowband Definitions for the allowable range of wavelengths.

Use the Radiometric Calibration tool or an atmospheric correction tool to calibrate the imagery to surface reflectance before computing this index. Reflectance values need to be scaled from 0 to 1. Edit the reflectance scale factor field in the ENVI header file (.hdr) as needed to scale the reflectance data from 0 to 1. Or, edit the output reflectance parameter in FLAASH.

Reference: Gitelson, A., et al. "Assessing Carotenoid Content in Plant Leaves with Reflectance Spectroscopy." Photochemistry and Photobiology 75 (2002): 272-281.

See Also

Spectral Indices, Vegetation Indices, Vegetation Analysis Tools, Vegetation and Its Reflectance Properties