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We developed a ground-based method for estimating leaf area index (LAI) and vertical distribution of leaf area density (LAD) for two Betula ermanii plots, combining an allometric method for tree leaf area with the MacArthurâHorn (MH) method using a portable laser rangefinder, including a correction for changes in leaf inclination angle along the vertical gradient measured with a portable digital protractor from a canopy access tower in each plot. Vertical distribution of projected leaf area density obtained by the MH method (LADMH) was transformed to relative distribution for allotting fixed LAI to different heights. Hence, we first developed an allometric method for estimating tree leaf area for LAI determination. Trunk cross-sectional area at branching height (AB) was accurately estimated (r = 0.97) from ground-based measurements of tree dimensions. We used this method to apply pipe model allometry between tree leaf area and AB, and estimated LAI (4.56 and 4.57 m m). We then examined how leaf inclination angle affected estimation of the vertical distribution of actual LAD. Leaf inclination angle measurements revealed that actual LAD in the upper canopy was 1.5â1.8-times higher than LADMH, because of steep leaf inclination, while the correction factor was 1.15â1.25 in the lower canopy. Due to the difference among heights, vertical distribution of LAD estimated with correction for vertical change in leaf inclination was more skewed to the upper canopy than that without correction. We also showed that error in LAD distribution can result if horizontal canopy heterogeneity is neglected when applying the MH method.22â2

Climate extremes impact the function, structure, and composition of terrestrial ecosystems, while ecosystem responses to climate extremes differ with variations in frequency, intensity, and timing of the extreme event. We examined the canopy recovery processes following a typhoon disturbance in a cool-temperate deciduous forest in northern Japan based on 6-year data of canopy coverage imagery using a digital cover photography (DCP) approach that estimates canopy metrics relevant to leaf and woody masses, spatial dynamics, or arrangement of foliage elements. The DCP-derived imagery detected increases in leaf area index and foliage cover within 2~3 years after the typhoon (i.e., recovery to the pre-typhoon state). Meanwhile, the recovery in leaf area and foliage cover observed after 6 years resulted from a spatial re-arrangement of the foliage elements (i.e., small within-crown gap fraction, foliage clumping) with increasing canopy space availability. Thus, the recovery of the spatial arrangement of foliage elements after the typhoon to the pre-typhoon state takes longer than the recovery of the leaf and woody masses. This study provides an important ecological implication in terms of possible resilience adaptation for ecosystem function and structure following extreme climate events. Key words: digital camera imagery, climate extremes, ecosystem resilience, spatial canopy dynamics, foliage clumping. Les conditions climatiques extremes ont un impact sur la fonction, la structure et la composition des ecosystemes terrestres tandis que les reactions des ecosystemes aux conditions climatiques extremes different selon la frequence, l'intensite des evenements extremes et le moment ou ils surviennent. Nous avons etudie les processus de recuperation du couvert forestier a la suite d'une perturbation causee par un typhon dans une foret decidue sous un climat frais tempere dans le nord-est du Japon. L'etude repose sur 6 annees de donnees d'imagerie du couvert forestier obtenues en utilisant la methode de la photographie numerique du couvert (PNC). Cette methode estime les metriques du couvert forestier pertinentes a la masse de la matiere ligneuse et du feuillage, a la dynamique spatiale ou a l'organisation spatiale des elements du feuillage. Les images derivees de la PNC ont detecte une augmentation de l'indice de surface foliaire et du couvert de feuillage 2 ou 3 ans apres le passage du typhon (c.-a-d. recuperation correspondant a la situation qui prevalait avant le passage du typhon). Pendant ce temps, la recuperation de la surface foliaire et du couvert de feuillage observee apres 6 ans etait le resultat d'une reorganisation spatiale des elements du feuillage (c.-a-d. faible proportion de trous a l'interieur de la cime et presence de touffes de feuilles) avec l'augmentation de la disponibilite de l'espace dans le couvert forestier. Par consequent, apres le passage du typhon le retour de l'organisation spatiale des elements du feuillage a ce qu'elle etait avant le typhon prend plus de temps que la recuperation de la masse de la matiere ligneuse et du feuillage. Cette etude a d'importantes implications ecologiques en termes d'adaptation potentielle de la resilience dans le cas de la fonction et de la structure des ecosystemes a la suite d'evenements climatiques extremes. [Traduit par la Redaction] Mots-cles : images provenant d'un appareil photo numerique, conditions climatiques extremes, resilience des ecosystemes, dynamique spatiale du couvert forestier, presence de touffes de feuilles., Introduction Canopy is the aggregate of the leaves and woody materials of twigs and branches over an ecosystem scale. Plant leaves are the most essential canopy element constraining photosynthetic assimilation [...]