Spectral Characteristics of Tree Components of Balsam Fir and Spruce Damaged by Spruce Budworm

Author： Leckie D. G. Ostaff D. P. Teillet P. M. Fedosjevs G.

Publisher： Society of American Foresters

ISSN： 0015-749X

Source： Forest Science, Vol.35, Iss.2, 1989-06, pp. : 582-600

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Abstract

Spectral reflectances from 360 to 1100 nm at 5 nm intervals in 6 nm bands were measured with a laboratory spectrometer for samples of the components of balsam fir and white spruce trees defoliated by the spruce budworm. These components included current-year needles, 1-year-old needles, 2-year and older needles, budworm feeding debris, twigs, bark, and lichen. Current-year needles had significantly higher reflectances than older needles in the green and yellow parts of the spectrum. Feeding debris, which is visually red, had a smooth spectral curve of increasing reflectance with wavelength. The greatest difference between needles and feeding debris was in the short near-infrared wavelengths and at the chlorophyll absorption maximum near 670 nm. The reflectance of twigs and bark changed with age and exposure to weathering. Variability in their reflectance was large. There were no distinct narrow band features of twig or feeding debris reflectance, which would be characteristic of defoliation. Lichen is highly reflective, and its presence on branches of defoliated trees will greatly alter branch reflectance characteristics. Changes in spectral reflectance of trees throughout the various stages of a spruce budworm outbreak depend on a complex interrelationship of the reflectances of individual components which, in turn, are complex and changing. For. Sci. 35(2):582-600.