AOBPreview originally published online on July 9, 2003
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Annals of Botany 92: 339-347, 2003
© 2003 Annals of Botany Company
Size Structure of Current-year Shoots in Mature Crowns
1 Graduate School of Agriculture, Kyoto University, Kitashirakawa Sakyoku, Kyoto 606-8502, Japan
* For correspondence. E-mail makizoh{at}hitohaku.jp 
Present address: Institute of Natural and Environmental Sciences, Himeji Institute of Technology, Yayoigaoka 6 Sanda Hyogo, 669-1546 Japan.
Received: 11 December 2002; Returned for revision: 8 April 2003; Accepted: 14 May 2003 Published electronically: 9 July 2003
Characteristics of current-year shoot populations were examined for three mature trees of each of three deciduous broad-leaved species. For first-order branches (branches emerging from the vertical trunk) of the trees examined, lengths or diameters of all current-year shoots were measured. Total leaf mass and total current-year stem mass of first-order branches were estimated using an allometric relationship between leaf or stem mass and length or diameter of current-year stems. For each tree, the number of current-year shoots on a first-order branch was proportional to the basal stem cross-sectional area of the branch. On the other hand, first-order branches had shoot populations with size structures similar to each other. As a result, the leaf mass of a first-order branch was proportional to the basal stem cross-sectional area of the branch, being compatible with the pipe-model relationship. All current-year shoot populations had positively skewed size structures. Because small shoots have a larger ratio of leaf mass to stem mass than large shoots, first-order branches had an extremely large ratio of leaf mass to current-year stem mass. This biased mass allocation will reduce costs for current stem production, respiration and future radial growth, and is beneficial to mature trees with a huge accumulation of non- photosynthetic organs. The allometric relationships between leaf mass and basal stem diameter and that between leaf mass and current-year stem mass of first-order branches were each similar across the trees examined. Characteristics of shoot populations tended to offset inter-species diversity of shoot allometry so that branch allometry shows inter-species convergence.
Key words: Allometry, Acer mono var. mayrii (Schwer.) Koidz., Betula maximowicziana Regel, biomass allocation, current-year shoot population, deciduous broad-leaved trees, first-order branch, mature crown, shoot size structure, pipe-model relationship, Quercus crispula Brume.