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The derivation of a simplified reflectance model for the estimation of leaf area index

Authors
Journal
Remote Sensing of Environment
0034-4257
Publisher
Elsevier
Publication Date
Volume
25
Issue
1
Identifiers
DOI: 10.1016/0034-4257(88)90041-7
Disciplines
  • Physics

Abstract

Abstract Information about crop reflectance obtained from the literature suggests that reflectance factors in the near-infrared are most suitable for estimating leaf area index (LAI). A problem arises if a multitemporal analysis is required. Soil moisture content is not constant during the season, and differences in soil moisture content greatly influence soil reflectance. A correction for soil background has to be made when ascertaining the relation between reflectance and crop characteristics. Since in the literature no satisfactory solution for correcting for soil background was found, an appropriate simplified reflectance model for estimating LAI is presented. First of all, an apparent plant cover is defined. Then, a corrected infrared reflectance is calculated by subtracting the contribution of the soil from the measured reflectance. The assumption that there is a constant ratio between the reflectances of bare soil in different spectral bands for a given soil background, independent of soil moisture content, enables the corrected infrared reflectance to be calculated without knowing soil reflectances. Subsequently, this corrected infrared reflectance is used for estimating LAI according to the inverse of a special case of the M Mitscherlich function. Simulations with the SAIL model confirmed the potential of this simplified (semi-empirical) reflectance model for estimating LAI.

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