LAI Measurement Protocols and Scaling

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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

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Basic principle for optical measurements of LAI
The modified Beers 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
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LAI-2000
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Gap fractions measured by LAI-2000
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New ground-based LAI instrument TRAC developed
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

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Tracing Radiation and Architecture of Canopies
(TRAC)
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TRAC for Measuring LAI
PPFD (mmol m-2 s-1)
WE LAI
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Constructing A Measured Canopy Gap Size
Accumulation Curve
For a random leaf spatial distribution
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Accumulated Gap Fraction in a Black Spruce Stand
Gaps between shoots inside crowns
Gaps between tree crowns
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Clumping Index (?) Derived After a Gap Removal
Technique
1Fm(0)-Fmr(0) ln Fm(0)
?
ln Fmr(0)
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LAI measurement protocols using optical
instruments
L is the leaf area index Le is the effective
LAI ? is the woody-to-total area ratio ?s is
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 ?s where 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

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Landsat scenes used for LAI validation across
Canada Summer, 1998
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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)

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Satellite-based LAI algorithm developmentCanada-w
ide LAI map validation involving all five forest
research centres and several universities(satelli
te Landsat ground data TRAC)
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SR-LAI relationships derived for Landsat TM
Mixed forest
Conifer
Crops
Deciduous
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Comparison of LAI maps from AVHRR and TM Both
resampled to 40 km pixels
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Scaling effects due to mixed pixels --a case with
mixture of sparse with with open land