Size-dependent differential scaling in branches: the mechanical design of trees revisited

SummarySize is a key factor in determining the mechanical and functional properties of any structure. Allometric analysis allows the comparison of dimensional form at different scales. Previous descriptions of branch scaling have attempted to define a single uniform relationship governing the proportions of trees and branches over their entire size range. A new general model of scaling in woody plants is proposed in which those plants and portions of plants below a certain critical size scale allometrically becoming more slender as size increases, while those above this limit become more robust as size increases. The basis for this differential scaling is the relationship between the bending mechanics of branches, the absolute size of the branch and possibly conductance requirements. Evidence for this model is derived from a review of size scaling in trees and shrubs and from a complete analysis of a silver maple (Acersaccharinum) 13 m in height and of 370 kg wet mass.

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