GEOSCAN, résultats de la recherche


TitreAssessing tree-ring carbon and oxygen stable isotopes for climate reconstruction in the Canadian northeastern boreal forest
TéléchargerTéléchargements (Prétirage)
AuteurBégin, C; Gingras, M; Savard, M M; Marion, J; Nicault, A; Bégin, Y
SourcePalaeogeography, Palaeoclimatology, Palaeoecology vol. 423, 2015 p. 91-101,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20130339
Documentpublication en série
Mediapapier; en ligne; numérique
SNRC23F/13; 23K/04; 23E/16; 23L/01
Lat/Long OENS -72.0000 -67.0000 56.0000 52.0000
Sujetsetudes isotopiques; isotopes d'oxygène; isotopes de carbone; temperature; géochimie; Nature et environnement
Illustrationslocation maps; graphs; plots; tables
ProgrammeDéveloppement durable des sables bitumineux, Géosciences environnementales
Résumé(disponible en anglais seulement)
In this study, we analyzed stable isotopes of oxygen (delta18O) and carbon (delta13C) of five black spruce (Picea mariana (Mill.) BSP) trees growing in the Québec boreal forest.We then produced the first dendroisotopic series covering the last two centuries (1800 - 2003) for this region where climatic records are particularly scarce and of short duration. Our aim was to evaluate the isotope sensitivity to climate and their potential as proxies for past climate conditions. The delta18O results showa strong coherence between all trees indicating that these values express a homogenous response at the site scale. For the delta13C series, slight inter-tree differences suggest the influence of micro-site conditions. Isotopic valueswere compared to climatic data for the period 1944 - 2003. These statistical analyses indicate that the delta13C and delta18O ratios are directly influenced by summer maximum temperatures but also correlate with parameters that integrate temperatures and moisture status. In all cases, the climate effects on delta13C values areweaker than the ones recorded by the delta18O series. Moreover, because the delta18O and delta13C values are sensitive to climatic variables that are linked and commonly associated in typical subarctic climate ambiances (warm-dry, cold-wet), the patterns of their joint response show stronger correlations with climatic parameters. Then, a temperature reconstruction was developed based on a regression model that calibrates the combined
delta13C and delta18O series against summer maximum temperature (TmaxJJA). The reconstructed summer temperatures indicates that the first half of the 19th centurywas the coldest period in the past 200 years and that a steadily change throughout milder conditions started in the early 1940's. These trends are consistent with other reconstructed values from independent proxies available for the same region. This research confirms that C and O dendroisotopic series of black spruce trees in high latitudes can document adequately past climatic
Résumé(Résumé en langage clair et simple, non publié)
Les isotopes stables des certains éléments tels le carbone et l'oxygène dans les cernes de croissance des arbres sont de plus en plus considérés comme de bons indicateurs des conditions environnementales et des impacts des activités humaines dans les écosystèmes forestiers. Une part importante de cette approche repose sur la séparation des signaux isotopiques reliés à la pollution de ceux reliés aux conditions naturelles, surtout d'origine climatique. La première étape est donc d'identifier quels sont les paramètres climatiques qui expliquent le mieux les variations des valeurs isotopiques dans des conditions naturelles et pour les mêmes espèces d'arbre utilisées dans les études de pollution. Nous avons donc exploré la signification climatique de séries isotopiques produites dans un site naturel de la forêt boréale canadienne.