Contrasting leaf phenological strategies optimize carbon gain under droughts of different duration

S. Manzoni, G. Vico, S. Thompson, F. Beyer, M. Weih

Research output: Contribution to journalArticle

15 Citations (Scopus)

Abstract

In most ecosystems, plants face periods with limited water availability, during which stomatal conductance is reduced to maintain hydration. However, prolonged dry spells might require more drastic strategies to conserve water, such as drought-deciduousness. If drought-related changes in leaf area are adaptive, it can be hypothesized that leaf area is optimized to maximize the growing-season carbon (C) gain. Different phenological strategies during drought have been proposed: (i) leaf area index (L) declines when net photosynthetic rates (A(net)) reach zero to maintain a non-negative A(net); (ii) L adjusts to avoid water potentials with negative impacts on A(net); (iii) a constant leaf water potential is maintained (isohydric behavior); and (iv) leaf area remains unaltered (i.e., summer-evergreen leaf habit). However, whether these strategies are optimal in terms of growing season C gains has not been assessed. Here we consider these theories in a unified framework using the same set of equations to describe gas exchanges and water transport in the soil plant atmosphere continuum, and quantify the effect of the leaf phenological strategy on plant C gain over the entire growing season in different climates. Longer dry periods tend to favor drought-deciduous rather than summer-evergreen habit. Deciduous plants that allow leaf water potential to fluctuate (anisohydric) while preventing negative A(net) assimilate more carbon than deciduous plants with fixed leaf water potentials (isohydric). Increased rooting depth allows evergreens to more effectively compete with drought-deciduous species. Moreover, increasing leaf nitrogen concentrations and thus photosynthetic capacity can be an effective acclimation strategy when dry periods are relatively short. (C) 2015 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)37-51
Number of pages15
JournalAdvances in Water Resources
Volume84
DOIs
Publication statusPublished - Oct 2015
Externally publishedYes

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