New insights into carbon allocation by trees from the hypothesis that annual wood production is maximized

• Published in: The New phytologist Vol. 199; no. 4; pp. 981 - 990
• Main Authors: McMurtrie, Ross E., Dewar, Roderick C.
• Format: Journal Article
• Language: English
• Published: England New Phytologist Trust 01.09.2013; Wiley Subscription Services, Inc
• Subjects: biomass; Canopies; Canopy; canopy photosynthesis; Carbon; Carbon - metabolism; carbon sequestration; Equation roots; Forest canopy; gross primary production; gross primary productivity; Hypotheses; Land use change; Leaf area; Leaf area index; Leaves; maximum wood production; Model testing; Models, Biological; Nitrogen; Nitrogen - metabolism; Optimization; optimization model; Photosynthesis; Picea - growth & development; Picea - metabolism; Picea abies; Pine trees; Plant Leaves - metabolism; Plant roots; Plant Roots - metabolism; Plants; Primary production; root nitrogen uptake; root systems; Rooting; rooting depth; Roots; Roots of functions; Soil depth; tree carbon allocation; trees; Trees - growth & development; Trees - metabolism; Uptake; Vertical profiles; Wood; Wood - growth & development; rooting depth; tree carbon allocation; optimization model; maximum wood production; leaf area index; canopy photosynthesis; root nitrogen uptake; gross primary production
• ISSN: 0028-646X; 1469-8137; 1469-8137
• DOI: 10.1111/nph.12344

Allocation of carbon (C) between tree components (leaves, fine roots and woody structures) is an important determinant of terrestrial C sequestration. Yet, because the mechanisms underlying C allocation are poorly understood, it is a weak link in current earth-system models. We obtain new theoretical insights into C allocation from the hypothesis (MaxW) that annual wood production is maximized. MaxW is implemented using a model of tree C and nitrogen (N) balance with a vertically resolved canopy and root system for stands of Norway spruce (Picea abies). MaxW predicts optimal vertical profiles of leaf N and root biomass, optimal canopy leaf area index and rooting depth, and the associated optimal pattern of C allocation. Key insights include a predicted optimal C–N functional balance between leaves at the base of the canopy and the deepest roots, according to which the net C export from basal leaves is just sufficient to grow the basal roots required to meet their N requirement. MaxW links the traits of basal leaves and roots to whole-tree C and N uptake, and unifies two previous optimization hypotheses (maximum gross primary production, maximum N uptake) that have been applied independently to canopies and root systems.