Journal Article

How should leaf area, sapwood area and stomatal conductance vary with tree height to maximize growth?

Thomas N. Buckley and David W. Roberts

in Tree Physiology

Volume 26, issue 2, pages 145-157
Published in print February 2006 | ISSN: 0829-318X
Published online February 2006 | e-ISSN: 1758-4469 | DOI:
How should leaf area, sapwood area and stomatal conductance vary with tree height to maximize growth?

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Conventional wisdom holds that the ratio of leaf area to sapwood area (L/S) should decline during height (H) growth to maintain hydraulic homeostasis and prevent stomatal conductance (gs) from declining. We contend that L/S should increase with H based on a numerical simulation, a mathematical analysis and a conceptual argument: (1) numerical simulation—a tree growth model, DESPOT (Deducing Emergent Structure and Physiology Of Trees), in which carbon (C) allocation is regulated to maximize C gain, predicts L/S should increase during most of H growth; (2) mathematical analysis—the formal criterion for optimal C allocation, applied to a simplified analytical model of whole tree carbon–water balance, predicts L/S should increase with H if leaf-level gas exchange parameters including gs are conserved; and (3) conceptual argument—photosynthesis is limited by several substitutable resources (chiefly nitrogen (N), water and light) and H growth increases the C cost of water transport but not necessarily of N and light capture, so if the goal is to maximize C gain or growth, allocation should shift in favor of increasing photosynthetic capacity and irradiance, rather than sustaining gs. Although many data are consistent with the prediction that L/S should decline with H, many others are not, and we discuss possible reasons for these discrepancies

Keywords: carbon allocation; hydraulic homeostasis; optimization; resource substitution

Journal Article.  0 words. 

Subjects: Plant Sciences and Forestry

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