Is the past history of acidic deposition in eastern Canada reflected in sugar maple's tree rings 87Sr/86Sr, Sr and Ca concentrations? [r-libre/2197]

Houle, Daniel; Marty, Charles; Gagnon, Christian; Bilodeau-Gauthier, Simon et Bélanger, Nicolas (2021). Is the past history of acidic deposition in eastern Canada reflected in sugar maple's tree rings 87Sr/86Sr, Sr and Ca concentrations?. Applied Geochemistry, 125, 104860. https://doi.org/10.1016/j.apgeochem.2020.104860

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Catégorie de document :	Articles de revues
Évaluation par un comité de lecture :	Oui
Étape de publication :	Publié
Résumé :	How calcium (Ca) uptake by trees in eastern Canadian forests has responded to decades of atmospheric acid deposition and its sharp decrease that started three decades ago is still largely unknown. Here, we tested a novel approach based on the measurements of Ca and strontium (Sr) concentrations and Sr isotope signature (87Sr/86Sr ratio) in sequential extracts of sugar maple tree rings and soils to assess changes in Ca availability and sources through time. The study was conducted at three sites showing a gradient of one order of magnitude in soil mineral weathering fluxes and exchangeable pools of Ca. We found that wood Ca and Sr concentrations increased with Ca and Sr concentrations in the exchangeable fraction (NH4Cl extracts) of the top mineral soil across sites. In addition, wood 87Sr/86Sr ratio was strongly correlated with 87Sr/86Sr ratio of this soil fraction. Both Ca and Sr concentrations in the exchangeable fraction of the wood decreased from pith to bark at all sites, whereas no trend was observed for the wood residual fraction. This was interpreted as a result of radial mobility of Ca in sapwood rather than a decline in the uptake of Ca and Sr by tree roots over time. The 87Sr/86Sr ratio of tree rings slightly increased over time only at the site with the higher soil exchangeable Ca pool, suggesting an increase in the contribution of soil mineral weathering relative to atmospheric deposition. In contrast with our hypothesis, our results show i) no evidence of pronounced changes in the relative contribution of the atmospheric vs. soil mineral weathering Ca components over time at the site with the smallest soil exchangeable Ca pools; and ii) the difficulty of assessing the temporal changes in the availability and the sources of Ca from sequential extractions of the wood due to a dynamic exchange process of Sr (and therefore Ca) between the exchangeable and residual fractions of the wood.
Adresse de la version officielle :	https://www.sciencedirect.com/science/article/pii/...
Déposant:	Bélanger, Nicolas
Responsable :	Nicolas Bélanger
Dépôt :	10 févr. 2021 15:13
Dernière modification :	10 févr. 2021 15:13

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