Carbon and oxygen isotopes of lakeshore black spruce trees in northeastern Canada as proxies for climatic reconstruction

In the boreal zone of northeastern Canada, paleoclimatic reconstructions of millennial length are rare and long isotopic climatic records are unavailable. However, millennial tree-ring series could be constructed within the region by cross-dating sub-fossil stems preserved in the littoral part of lakes. Thus, there is a need to evaluate the potential of using stable isotopes of lakeshore black spruce trees (Picea mariana [Mill] B.S.P.) as proxies for climatic reconstruction. We collected four living riparian black spruce trees and we investigated the inter- and intra-tree correlations for four trees, at two different sampling heights (1 and 4 m), for their carbon (δ13C) and oxygen (δ18O) isotopes, as a test for potential long-term reconstruction. A significant correlation (Pearson coefficient) for the isotopic series was found for the two sampling heights (r = 0.92 for δ13C; 0.65 for δ18O), and between the four trees. We further assessed the climatic significance of the mean of the four trees. The strongest correlation of the δ13C series was with the mean of June to August vapor pressure deficit (VPD; r = 0.50), and the δ18O values with the June to August climatic index and June to July maximal temperature (r = − 0.61 and 0.55, respectively). This study suggests that δ18O series of riparian black spruce trees, and eventually their sub-fossil counterparts, can be used as proxies for reconstructing long climatic series in northeastern Canada.