Estimation of leaf area index in eucalypt forest using digital photography

Elsevier Science Bv
Publication Type:
Journal Article
Agricultural And Forest Meteorology, 2007, 143 (3-4), pp. 176 - 188
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We tested whether leaf area index (L) in eucalypt vegetation could be accurately estimated from gap fraction measurements made using both fisheye and non-fisheye digital photography. We compared methods that measure the gap fraction at a single zenith angles. We applied these methods in an unthinned stand of the broadleaf tree species Ecualyptus marginata that had an intial L of 3. We removed one-third of the trees and reapplied the methods, and then removed another one-third of the trees and applied the methods a tjird time. L from the photographic methods was compared to L obtained from destrictive sampling and allometry. We found that L was accurately estimated from non-fisheye images taken at the zenith, providing thaty the total gap fraction was divided into large, between-crown gaps and smaller, within-crown gaps, prior to using the Beer-Lambert law to estimate L. This rapid and simpel method corrected for foliage clumping and provided estimates of crown porosity, crown cover, foliage cover and the foliage clumping index at the zenith, but required an assumption about the lgiht extenction coefficient at the zenith. Fisheye photography also provided good estimates of L bit only if the images were corrected for the gamma function of the digital camera, and the combined Chen-Chilar and Lang-Xiang method of correcting for foliage prjection coefficient was. Method of obtaining and analysising gap fraction and gap size distributions from fisheye photography need further improvement to separate the effects of foliage clumping and leaf angle distribution.
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