© 2007 Heron Publishing—Victoria, Canada
Evidence for age- and size-mediated controls of tree growth from grafting studies
Maurizio Mencuccini (1, 2), Jordi Martínez-Vilalta (1, 3), H. A. Hamid (1), E. Korakaki (1) and D. Vanderklein (1, 4)
1. School of GeoSciences, University of Edinburgh, Edinburgh EH9 3JN, U.K. / 2. Corresponding author (m.mencuccini@ed.ac.uk) / 3. CREAF/Unitat d’Ecologia, Universitat Autònoma de Barcelona, Edifici C (Facultat de Ciències), Bellaterra 08193, Barcelona,
Spain / 4. Department of Biology and Molecular Biology, Montclair State University, Montclair, NJ, USA / Received March 14, 2006; accepted June 20, 2006; published online December 1, 2006
Summary
Vegetative propagation techniques such as grafting can be used, in conjunction with field studies, to decouple the relative
effects of age and size on tree metabolism and growth. Despite interest in this approach, little attention has been paid to
the best metrics for assessing the growth performance of grafted plants over time. Based on an analysis of the grafting literature
and our own data, we show that the choice of metrics to assess tree growth can entirely change the conclusions reached about
the relative importance of age versus size. We recommend that absolute as well as relative rates of growth are calculated
and that scion size be standardized as much as possible at the start of the experiment. Once proper metrics are chosen, all
of the available published evidence is largely concordant with two concepts: (1) age-mediated controls of tree growth are
likely to be important during the first few years of a tree’s life (before phase change); and (2) after the first few years
of a tree’s life, size-mediated factors largely prevail over age-mediated factors in determining tree growth rates. We found
no support for theories invoking age-mediated sink limitations in old trees.
Keywords:
aging, age-related processes, grafting, hydraulic limitation hypothesis, relative growth rate, size-related processes.
