Influence of shade tolerance and development stage on the allometry of ten temperate tree species |
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Authors: | Tony Franceschini Robert Schneider |
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Affiliation: | 1. Département de Biologie, Chimie et Géographie, Chaire de Recherche sur la Forêt Habitée, Université du Québec à Rimouski (UQAR), 300 allée des Ursulines, Rimouski, QC, G5L 3A1, Canada
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Abstract: | Allometry studies the change in scale between two dimensions of an organism. The metabolic theory of ecology predicts invariant allometric scaling exponents, while empirical studies evidenced inter- and intra-specific variations. This work aimed at identifying the sources of variations of the allometric exponents at both inter- and intra-specific levels using stem analysis from 9,363 trees for ten Eastern Canada species with a large shade-tolerance gradient. Specifically, the yearly allometric exponents, α v,DBH [volume (v) and diameter at breast height (DBH)], β v,h [v and height (h)], and γ h,DBH (h and DBH) were modelled as a function of tree age for each species. α v,DBH, and γ h,DBH increased with tree age and then reached a plateau ranging from 2.45 to 3.12 for α v,DBH, and 0.874–1.48 for γ h,DBH. Pine species presented a local maximum. No effect of tree age on β v,h was found for conifers, while it increased until a plateau ranging from 3.71 to 5.16 for broadleaves. The influence of shade tolerance on the growth trajectories was then explored. In the juvenile stage, α v,DBH, and γ h,DBH increased with shade tolerance while β v,h was shade-tolerance independent. In the mature stage, β v,h increased with shade tolerance, whereas γ h,DBH decreased and α v,DBH was shade-tolerance independent. The interaction between development stage and shade tolerance for allometric exponents demonstrates the importance of the changing functional requirements of trees for resource allocation at both the inter- and intra-specific level. These results indicate the need to also integrate specific functional traits, growth strategies and allocation, in allometric theoretical frameworks. |
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