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Precipitation alters the CO2 effect on water-use efficiency of temperate forests.
Belmecheri, Soumaya; Maxwell, R Stockton; Taylor, Alan H; Davis, Kenneth J; Guerrieri, Rossella; Moore, David J P; Rayback, Shelly A.
Afiliação
  • Belmecheri S; Laboratory of Tree Ring Research, University of Arizona, Tucson, AZ, USA.
  • Maxwell RS; Department of Geospatial Science, Radford University, Radford, VA, USA.
  • Taylor AH; Department of Geography and Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA, USA.
  • Davis KJ; Department of Meteorology and Atmospheric Science and Earth and Environmental Systems Institute, The Pennsylvania State University, University Park, PA, USA.
  • Guerrieri R; Department of Agricultural and Food Sciences (DISTAL), University of Bologna, Bologna, Italy.
  • Moore DJP; School of Natural Resources and the Environment, University of Arizona, Tucson, AZ, USA.
  • Rayback SA; Department of Geography, University of Vermont, Burlington, VT, USA.
Glob Chang Biol ; 27(8): 1560-1571, 2021 04.
Article em En | MEDLINE | ID: mdl-33464665
ABSTRACT
Increasing water-use efficiency (WUE), the ratio of carbon gain to water loss, is a key mechanism that enhances carbon uptake by terrestrial vegetation under rising atmospheric CO2 (ca ). Existing theory and empirical evidence suggest a proportional WUE increase in response to rising ca as plants maintain a relatively constant ratio between the leaf intercellular (ci ) and ambient (ca ) partial CO2 pressure (ci /ca ). This has been hypothesized as the main driver of the strengthening of the terrestrial carbon sink over the recent decades. However, proportionality may not characterize CO2 effects on WUE on longer time-scales and the role of climate in modulating these effects is uncertain. Here, we evaluate long-term WUE responses to ca and climate from 1901 to 2012 CE by reconstructing intrinsic WUE (iWUE, the ratio of photosynthesis to stomatal conductance) using carbon isotopes in tree rings across temperate forests in the northeastern USA. We show that iWUE increased steadily from 1901 to 1975 CE but remained constant thereafter despite continuously rising ca . This finding is consistent with a passive physiological response to ca and coincides with a shift to significantly wetter conditions across the region. Tree physiology was driven by summer moisture at multi-decadal time-scales and did not maintain a constant ci /ca in response to rising ca indicating that a point was reached where rising CO2 had a diminishing effect on tree iWUE. Our results challenge the mechanism, magnitude, and persistence of CO2 's effect on iWUE with significant implications for projections of terrestrial productivity under a changing climate.
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Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Dióxido de Carbono / Água Tipo de estudo: Prognostic_studies Idioma: En Ano de publicação: 2021 Tipo de documento: Article

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Assunto principal: Dióxido de Carbono / Água Tipo de estudo: Prognostic_studies Idioma: En Ano de publicação: 2021 Tipo de documento: Article