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 |
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| Authors: | 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 Panyushkina Heather 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 |
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| Institution: | 1. Department of Forest Ecosystems & Society, Oregon State University, Corvallis, OR, USA;2. Western Ecology Division, National Health and Environmental Effects Research Laboratory (NHEERL), U.S. Environmental Protection Agency, Corvallis, OR, USA;3. U.S.D.A. Forest Service, Pacific Northwest Research Station, Corvallis, OR, USA;4. Jack Baskin Engineering, University of California Santa Cruz, Santa Cruz, CA, USA;5. New Zealand Forest Research Institute (SCION), Rotorua, New Zealand;6. Department of Environmental, Biological and Pharmaceutical Sciences and Technologies (DiSTABiF), Second University of Naples, Caserta, Italy;7. Ecole Pratique des Hautes Etudes, Centre for Bio‐Archaeology and Ecology, Institut de Botanique, University of Montpellier 2, Montpellier, France;8. Department of Ecology and Evolutionary Biology, University of Kansas, Lawrence, KS, USA;9. Department of Animal and Plant Sciences, University of Sheffield, Sheffield, UK;10. UMR1202 BIOGECO, INRA, Cestas, France;11. UMR 1202 BIOGECO, University of Bordeaux, Pessac, France;12. National Research Program, Water Mission Area, U.S. Geological Survey, Reston, VA, USA;13. Department of Integrative Biology, University of California Berkeley, Berkeley, CA, USA;14. Bordeaux Sciences Agro, UMR ISPA 1391, INRA, Gradignan, France;15. Nicholas School of the Environment, Duke University, Durham, NC, USA;16. Department of Forestry, University of Missouri, Columbia, MO, USA;17. Institute of Botany, University of Basel, Basel, Switzerland;18. UMR1391 ISPA, INRA, Villenave d'Ornon, France;19. Laboratory for Tree‐Ring Research, University of Arizona, Tucson, AZ, USA;20. Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences, Alnarp, Sweden;21. Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Ume?, Sweden;22. Department of Forest, Rangeland and Fire Sciences, University of Idaho, Moscow, ID, USA;23. Paul Scherrer Institute, Villigen, Switzerland;24. School of the Environment, Natural Resources and Geography, Bangor University, Gwynedd, UK;25. Centre for Forest Interdisciplinary Research (C‐FIR), University of Winnipeg, Winnipeg, MB, Canada;26. Department of Earth & Environmental Sciences, California State University, Fresno, CA, USA |
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| Abstract: | 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. |
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| Keywords: | angiosperm carbon dioxide free‐air CO2 enrichment gymnosperm optimal stomatal behavior photosynthesis stomatal conductance water use efficiency |
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