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Spectral changes in conifers subjected to air pollution and water stress: Experimental studiesThe roles of leaf anatomy, moisture and pigment content, and number of leaf layers on spectral reflectance in healthy, pollution-stressed, and water-stressed conifer needles were examined experimentally. Jeffrey pine (Pinus jeffreyi) and giant sequoia (Sequoiadendron gigantea) were exposed to ozone and acid mist treatments in fumigation chambers; red pine (Pinus resinosa) needles were artificially dried. Infrared reflectance from stacked needles rose with free water loss. In an air-drying experiment, cell volume reductions induced by loss of turgor caused near-infrared reflectance (TM band 4) to drop after most free water was lost. Under acid mist fumigation, stunting of tissue development similarly reduced band 4 reflectance. Both artificial drying and pollutant fumigation caused a blue shift of the red edge of spectral reflectance curves in conifers, attributable to chlorophyll denaturation. Thematic mapper band ratio 4/3 fell and 5/4 rose with increasing pollution stress on artificial drying. Loss of water by air-drying, freeze-drying, or oven-drying enhanced spectral features, due in part to greater scattering and reduced water absorption. Grinding of the leaf tissue further enhanced the spectral features by increasing reflecting surfaces and path length. In a leaf-stacking experiment, an asymptote in visible and infrared reflectance was reached at 7-8 needle layers of red pine.
Document ID
19880037705
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Westman, Walter E.
(NASA Ames Research Center Moffett Field; California, University, Berkeley, United States)
Price, Curtis V.
(USGS, Water Resources Div., Trenton NJ, United States)
Date Acquired
August 13, 2013
Publication Date
January 1, 1988
Publication Information
Publication: IEEE Transactions on Geoscience and Remote Sensing
Volume: 26
ISSN: 0196-2892
Subject Category
Earth Resources And Remote Sensing
Accession Number
88A24932
Distribution Limits
Public
Copyright
Other

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