North America’s oldest boreal trees are more efficient water users due to increased [CO2], but do not grow faster

Giguère-Croteau, Claudie; Boucher, Étienne et Bergeron, Yves (2019). « North America’s oldest boreal trees are more efficient water users due to increased [CO2], but do not grow faster ». Proceedings of the National Academy of Sciences, pp. 1-6.

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Résumé

Due to anthropogenic emissions and changes in land use, trees are now exposed to atmospheric levels of [CO2] that are unprecedented for 650,000 y [Lüthi et al. (2008) Nature 453:379–382] (thousands of tree generations). Trees are expected to acclimate by modulating leaf–gas exchanges and alter water use efficiency which may result in forest productivity changes. Here, we present evidence of one of the strongest, nonlinear, and unequivocal postindustrial increases in intrinsic water use efficiency (iWUE) ever documented (+59%). A dual-isotope tree-ring analysis (δ13C and δ18O) covering 715 y of growth of North America’s oldest boreal trees (Thuja occidentalis L.) revealed an unprecedented increase in iWUE that was directly linked to elevated assimilation rates of CO2 (A). However, limited nutrient availability, changes in carbon allocation strategies, and changes in stomatal density may have offset stem growth benefits awarded by the increased iWUE. Our results demonstrate that even in scenarios where a positive CO2 fertilization effect is observed, other mechanisms may prevent trees from assimilating and storing supplementary anthropogenic emissions as above-ground biomass. In such cases, the sink capacity of forests in response to changing atmospheric conditions might be overestimated.

Type: Article de revue scientifique
Mots-clés ou Sujets: water use efficiency carbon dioxide stable isotopes Productivity Boreal forest
Unité d'appartenance: Centres institutionnels > Centre de recherche en géochimie et géodynamique (GEOTOP)
Déposé par: Etienne Boucher
Date de dépôt: 01 févr. 2019 09:36
Dernière modification: 01 févr. 2019 09:36
Adresse URL : http://archipel.uqam.ca/id/eprint/12160

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