A dynamic leaf gas-exchange strategy is conserved in woody plants under changing ambient CO2: Evidence from carbon isotope discrimination in paleo and CO2 enrichment studies

Steven L. Voelker, J. Renée Brooks, Frederick C. Meinzer, Rebecca Anderson, Martin K.F. Bader, Giovanna Battipaglia, Katie M. Becklin, David Beerling, Didier Bert, Julio L. Betancourt, Todd E. Dawson, Jean Christophe Domec, Richard P. Guyette, Christian Körner, Steven W. Leavitt, Sune Linder, John D. Marshall, Manuel Mildner, Jérôme Ogée, Irina PanyushkinaHeather J. Plumpton, Kurt S. Pregitzer, Matthias Saurer, Andrew R. Smith, Rolf T.W. Siegwolf, Michael C. Stambaugh, Alan F. Talhelm, Jacques C. Tardif, Peter K. Van de Water, Joy K. Ward, Lisa Wingate

Research output: Contribution to journalArticlepeer-review

102 Scopus citations


Rising atmospheric [CO2], ca, is expected to affect stomatal regulation of leaf gas-exchange of woody plants, thus influencing energy fluxes as well as carbon (C), water, and nutrient cycling of forests. Researchers have proposed various strategies for stomatal regulation of leaf gas-exchange that include maintaining a constant leaf internal [CO2], ci, a constant drawdown in CO2 (ca - ci), and a constant ci/ca. These strategies can result in drastically different consequences for leaf gas-exchange. The accuracy of Earth systems models depends in part on assumptions about generalizable patterns in leaf gas-exchange responses to varying ca. The concept of optimal stomatal behavior, exemplified by woody plants shifting along a continuum of these strategies, provides a unifying framework for understanding leaf gas-exchange responses to ca. To assess leaf gas-exchange regulation strategies, we analyzed patterns in ci inferred from studies reporting C stable isotope ratios (δ13C) or photosynthetic discrimination in woody angiosperms and gymnosperms that grew across a range of ca spanning at least 100 ppm. Our results suggest that much of the ca-induced changes in ci/ca occurred across ca spanning 200 to 400 ppm. These patterns imply that ca - ci will eventually approach a constant level at high ca because assimilation rates will reach a maximum and stomatal conductance of each species should be constrained to some minimum level. These analyses are not consistent with canalization toward any single strategy, particularly maintaining a constant ci. Rather, the results are consistent with the existence of a broadly conserved pattern of stomatal optimization in woody angiosperms and gymnosperms. This results in trees being profligate water users at low ca, when additional water loss is small for each unit of C gain, and increasingly water-conservative at high ca, when photosystems are saturated and water loss is large for each unit C gain.

Original languageEnglish (US)
Pages (from-to)889-902
Number of pages14
JournalGlobal Change Biology
Issue number2
StatePublished - Feb 1 2016
Externally publishedYes


  • Angiosperm
  • Carbon dioxide
  • Free-air CO enrichment
  • Gymnosperm
  • Optimal stomatal behavior
  • Photosynthesis
  • Stomatal conductance
  • Water use efficiency

ASJC Scopus subject areas

  • Global and Planetary Change
  • Environmental Chemistry
  • Ecology
  • General Environmental Science


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