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TitleLeaf area index of boreal forests: theory, techniques, and measurements
AuthorChen, J M; Rich, P M; Gower, S T; Norman, J M; Plummer, S
SourceBOREAS special issue; Journal of Geophysical Research vol. 102, no. D24, 1997 p. 29,429-29,443, Open Access
logo Open Access
Alt SeriesEarth Sciences Sector, Contribution Series 20041748
Mediapaper; on-line; digital
File formatpdf
ProvinceSaskatchewan; Manitoba
NTS63J; 63K; 63L; 63M; 63N; 63O; 63P; 106I; 106P
AreaPrince Albert; Candle Lake; Thompson; Nelson House
Lat/Long WENS-106.0000 -98.5000 56.0000 53.7500
Subjectsvegetation; vegetation history; biomes; remote sensing
Illustrationsequations; tables; graphs
ProgramBoreal Ecosystem-Atmosphere Study (BOREAS)
Released1997 12 01
AbstractLeaf area index (LAI) is a key structural characteristic of forest ecosystems because of the role of green leaves in controlling many biological and physical processes in plant canopies. Accurate LAI estimates are required in studies of ecophysiology, atmosphere-ecosystem interactions, and global change. The objective of this paper is to evaluate LAI values obtained by several research teams using different methods for a broad spectrum of boreal forest types in support of the international Boreal Ecosystem-Atmosphere Study (BOREAS). These methods include destructive sampling and optical instruments: the tracing radiation and architecture of canopies (TRAC), the LAI-2000 plant canopy analyzer, hemispherical photography, and Sunfleck Ceptometer. The latter three calculate LAI form measured radiation transmittance (gap fraction) using inversion models that assume a random spatial distribution of leaves. It is shown that these instruments underestimate LAI of boreal forest stands where the foliage is clumped. The TRAC quantifies the clumping effect by measuring the canopy gap size distribution. For deciduous stands the clumping index measured from TRAC includes the clumping effect at all scales, but for conifer stands it only resolves the clumping effect at scales larger than the shoot (the basic collection of needles). To determine foliage clumping within conifer shoots, a video camera and rotational light table system was used. The major difficulties in determining the surface area of small conifer needle have been largely overcome by the use of an accurate volume displacement method. Hemispherical photography has the advantage that is also provides a permanent image record of the canopies. Typically, LAI falls in the range from 1 to 4 for jack pine and aspen forests and from 1 to 6 for black spruce. Our comparative studies provide the most comprehensive set of LAI estimates available for boreal forests and demonstrate that optical techniques, combined with limited direct foliage sampling, can be used to obtain quick and accurate LAI measurements.

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