Biophysical and biochemical sources of variability in canopy reflectance

Research output: Contribution to journalArticle

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Abstract

Analyses of various biophysical and biochemical factors affecting plant canopy reflectance have been carried out over the past few decades, yet the relative importance of these factors has not been adequately addressed. A combination of field and modeling techniques were used to quantify the relative contribution, of leaf, stem, and litter optical properties (incorporating known variation in foliar biochemical properties) and canopy structural attributes to nadir-viewed vegetation reflectance data. Variability in tissue optical properties was wavelength-dependent. For green foliage, the lowest variation was in the visible (VIS) spectral region and the highest in the near-infrared (NIR). For standing litter material, minimum variation occurred in the VIS/NIR, while the largest differences were observed in the shortwave-IR (SWIR). Woody stem material showed opposite trends, with lowest variation in the SWIR and highest in the NIR. Leaf area index (LAI) and leaf angle distribution (LAD) were the dominant controls on canopy reflectance data with the exception of soil reflectance and vegetation cover in sparse canopies. Leaf optical properties (and thus foliar chemistry) were expressed most directly at the canopy level in the NIR, but LAI and LAD strongly controlled the relationship between leaf and canopy spectral characteristics. Stem material played a small but significant role in determining canopy reflectance in woody plant canopies, especially those with LAI<5.0. Standing litter significantly affected the reflectance characteristics of grassland canopies; small increases in the percentage of standing litter had a disproportionately large affect on canopy reflectance. The structural attributes of ecosystems determine the relative contribution of tissue, canopy, and landscape factors that drive variation in a reflectance signal. Deconvolution of these factors requires an understanding of the sources of variance at each scale (which is ecosystem dependent) as well as an adequate sampling (spectral, angular, and temporal) of the shortwave (400-2500 nm) spectrum.

Original languageEnglish (US)
Pages (from-to)234-253
Number of pages20
JournalRemote Sensing of Environment
Volume64
Issue number3
DOIs
StatePublished - Jun 1 1998
Externally publishedYes

Fingerprint

canopy reflectance
reflectance
canopy
near infrared
litter
leaf area index
optical property
Infrared radiation
stem
optical properties
Optical properties
leaf angle
Ecosystems
Tissue
ecosystem
stems
leaves
nadir
deconvolution
woody plant

ASJC Scopus subject areas

  • Soil Science
  • Geology
  • Computers in Earth Sciences

Cite this

Biophysical and biochemical sources of variability in canopy reflectance. / Asner, Gregory P.

In: Remote Sensing of Environment, Vol. 64, No. 3, 01.06.1998, p. 234-253.

Research output: Contribution to journalArticle

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