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Applied Optics

Applied Optics

APPLICATIONS-CENTERED RESEARCH IN OPTICS

  • Vol. 41, Iss. 36 — Dec. 20, 2002
  • pp: 7667–7670

Correction to the plant canopy gap-size analysis theory used by the Tracing Radiation and Architecture of Canopies instrument

Sylvain G. Leblanc  »View Author Affiliations


Applied Optics, Vol. 41, Issue 36, pp. 7667-7670 (2002)
http://dx.doi.org/10.1364/AO.41.007667


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Abstract

A plant canopy gap-size analyzer, the Tracing Radiation and Architecture of Canopies (TRAC), developed by Chen and Cihlar [Appl. Opt. 34, 6211 (1995)] and commercialized by 3rd Wave Engineering (Nepean, Canada), has been used around the world to quantify the fraction of photosynthetically active radiation absorbed by plant canopies, the leaf area index (LAI), and canopy architectural parameters. The TRAC is walked under a canopy along transects to measure sunflecks that are converted into a gap-size distribution. A numerical gap-removal technique is performed to remove gaps that are not theoretically possible in a random canopy. The resulting reduced gap-size distribution is used to quantify the heterogeneity of the canopy and to improve LAI measurements. It is explicitly shown here that the original derivation of the clumping index was missing a normalization factor. For a very clumped canopy with a large gap fraction, the resulting LAI can be more than 100% smaller than previously estimated. A test case is used to demonstrate that the new clumping index derivation allows a more accurate change of LAI to be measured.

© 2002 Optical Society of America

OCIS Codes
(010.3920) Atmospheric and oceanic optics : Meteorology
(280.0280) Remote sensing and sensors : Remote sensing and sensors

History
Original Manuscript: September 9, 2002
Published: December 20, 2002

Citation
Sylvain G. Leblanc, "Correction to the plant canopy gap-size analysis theory used by the Tracing Radiation and Architecture of Canopies instrument," Appl. Opt. 41, 7667-7670 (2002)
http://www.opticsinfobase.org/ao/abstract.cfm?URI=ao-41-36-7667


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References

  1. J. M. Chen, J. Cihlar, “Plant canopy-gap size analysis theory for improving optical measurements of leaf-area index,” Appl. Opt. 34, 6211–6222 (1995). [CrossRef] [PubMed]
  2. T. Nilson, “A theoretical analysis of the frequency of gaps in plant stands,” Agri. Meteorol. 8, 25–38 (1971). [CrossRef]
  3. J. M. Chen, “Optically-based methods for measuring seasonal variation in leaf area index of boreal conifer forests,” Agri. For. Meteorol. 80, 135–163 (1996). [CrossRef]
  4. E. E. Miller, J. M. Norman, “A sunfleck theory for plant canopies. I. Length of sunlit segments along a transect,” Agron. J. 63, 735–738 (1971). [CrossRef]
  5. J. M. Chen, P. M. Rich, T. S. Gower, J. M. Norman, S. Plummer, “Leaf area index of boreal forests: theory, techniques and measurements.” J. Geophys. Res. 102, 29429–29444 (1997). [CrossRef]
  6. S. G. Leblanc, J. M. Chen, M. Kwong, TRAC Manual (Version 2.1) (Canada Centre for Remote Sensing, Natural Resources Canada, Ottawa, Canada, 2002).
  7. B. E. Law, S. Van Tuyl, A. Cescatti, D. D. Baldocchi, “Estimation of leaf area index in open-canopy ponderosa pine forests at different successional stages and management regimes in Oregon,” Agri. For. Meteorol. 108, 1–14 (2001). [CrossRef]

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