| Title | Leaf area index of boreal forests: theory, techniques, and measurements |
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| Author | Chen, J M; Rich, P M; Gower, S T; Norman, J M; Plummer, S |
| Source | BOREAS special issue; Journal of Geophysical Research vol. 102, no. D24, 1997 p. 29,429-29,443, https://doi.org/10.1029/97JD01107  Open Access |
| Image |  |
| Year | 1997 |
| Alt Series | Earth Sciences Sector, Contribution Series 20041748 |
| Publisher | Wiley-Blackwell |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Saskatchewan; Manitoba |
| NTS | 63J; 63K; 63L; 63M; 63N; 63O; 63P; 106I; 106P |
| Area | Prince Albert; Candle Lake; Thompson; Nelson House |
| Lat/Long WENS | -106.0000 -98.5000 56.0000 53.7500 |
| Subjects | vegetation; vegetation history; biomes; remote sensing |
| Illustrations | equations; tables; graphs |
| Program | Boreal Ecosystem-Atmosphere Study (BOREAS) |
| Released | 1997 12 01 |
| Abstract | Leaf 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. |
| GEOSCAN ID | 218550 |
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