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LAI Measurement Protocols and Scaling

LAI Measurement Protocols and Scaling. Jing M. Chen University of Toronto Ontario, Canada. Josef Cihlar, Sylvain Leblanc, Richard Fernandes, Goran Palvlic Canada Centre for Remote Sensing. Basic principle for optical measurements of LAI. The modified Beer’s Law:

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LAI Measurement Protocols and Scaling

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  1. LAI Measurement Protocols and Scaling Jing M. Chen University of Toronto Ontario, Canada Josef Cihlar, Sylvain Leblanc, Richard Fernandes, Goran Palvlic Canada Centre for Remote Sensing

  2. Basic principle for optical measurements of LAI The modified Beer’s Law: where  is the zenith angle, G() is the projection coefficient  is the clumping index L is the leaf area index Le=  L, effective LAI

  3. LAI-2000 Open Forest Dense Forest Gap fraction View Zenith Angle

  4. Gap fractions measured by LAI-2000

  5. New ground-based LAI instrument TRACdeveloped at CCRS and commercialized by the Third-Wave Engineering. It becomes a new international standard • Purpose: • LAI • new theory: • gap size distribution • new measurement • concept: • solar beam as probe • new parameter: • clumping index • spin-off: • FPAR and canopy • architectural parameters

  6. Tracing Radiation and Architecture of Canopies (TRAC)

  7. TRAC for Measuring LAI PPFD (mmol m-2 s-1) WE LAI

  8. Constructing A Measured Canopy Gap Size Accumulation Curve For a random leaf spatial distribution:

  9. Accumulated Gap Fraction in a Black Spruce Stand Gaps between shoots inside crowns Gaps between tree crowns

  10. Clumping Index () Derived After a Gap Removal Technique [1+Fm(0)-Fmr(0)] ln [Fm(0)]  = ln [Fmr(0)]

  11. LAI measurement protocols using optical instruments L is the leaf area index Le is the effective LAI  is the woody-to-total area ratio sis the needle-to-shoot area ratio E is the clumping index at scales larger than shoots • Recommended protocols: • Use LAI-2000 to measure Le • Use TRAC to measure E for all forest stands and shrubs • Measure swhere possible, otherwise the default value is 1.4 for boreal conifer, and 1.8 for temperate conifer. For broadleaf forests, s=1.0 • Measure  where possible, otherwise use allometric equations or estimates

  12. Landsat scenes used for LAI validation across Canada Summer, 1998

  13. LAI Map Validation A team was formed in 1997 and measurements of LAI/FPAR began in 1997 and expanded in 1998. • Drs. Jing Chen, Josef Cihlar and Lernard Brown, CCRS, Ontario (conifer, deciduous forests) • Dr. Joost Vandersanden, CCRS, Ontario (crops). • Drs. Andy Black and Michael Novak, UBC, British Columbia. (conifer forest and crop) • Dr. Robert Fleming, CFS, Sault Ste Marie, Ontario (plantations and forests) • Dr. Gilles Robitaille, CFS, Saint-Foy, Quebec (deciduous and conifer forests) • Dr. Ron Hall, CFS, Edmonton, Alberta (deciduous and conifer forests) • Dr. Derek Peddle, Lethbridge, Alberta (deciduous and conifer forests) • Drs. Edwin Swift and Joan Luther, CFS, New Brunswick (conifer, deciduous forests, grassland) • Dr. Harry McCaughey, Queen's University, Ontario (conifer, decidous forests) • Drs. Tony Trofymovv and Gordon Frazer, CFS, BC. (conifer forests)

  14. Satellite-based LAI algorithm developmentCanada-wide LAI map validation involving all five forest research centres and several universities(satellite: Landsat; ground data: TRAC)

  15. SR-LAI relationships derived for Landsat TM Mixed forest Conifer Deciduous Crops

  16. Comparison of LAI maps from AVHRR and TM Both resampled to 40 km pixels

  17. Scaling effects due to mixed pixels --a case with mixture of sparse with with open land

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