Direct and indirect estimates of Leaf Area Index (LAI) for lodgepole and loblolly pine stands |
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Authors: | David Arthur Sampson H Lee Allen |
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Institution: | (1) Department of Forestry, North Carolina State University, 27695-8008 Raleigh, NC, USA |
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Abstract: | We compared direct and indirect estimates of leaf area index (LAI) for lodgepole and loblolly pine stands. Indirect estimates
of LAI using radiative methods of the LI-COR LAI-2000 Plant Canopy Analyzer (PCA) did not correlate with allometric estimates
for lodgepole pine, and correlated only weakly with litter-trap estimates for loblolly pine. The PCA consistently under-estimated
LAI in lodgepole pine stands with high LAI, and over-estimated LAI in the loblolly pine stands with low LAI. We developed
a physical model to test the hypothesis that the PCA may under-estimate LAI in high leaf area stands because of increased
foliage overlap and, therefore, increased selfshading. Radiative estimates of LAI using the PCA for the physical model were
consistenly lower than allometric measures. Results from the physical model suggested that increased foliage overlap decreased
the ability of the PCA to accurately estimate LAI. The relationship between allometric and radiative measures suggested an
upper asymptote in LAI estimated using the PCA. The PCA may not accurately estimate LAI in stands of low or high leaf area
index, and the bias or error associated with these estimates probably depends on species and canopy structure. A species specific
correction factor will not necessarily correct bias in LAI estimates using the PCA. |
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Keywords: | Self-shading Radiative techniques Canopy architecture |
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