Tree-Ring Nitrogen Isotopes Reflect Anthropogenic NOX Emissions and Climatic Effects

详细信息    查看全文

• 作者：Martine M. Savard ; Christian Bgin ; Anna Smirnoff ; Jolle Marion ; Elise Rioux-Paquette
• 刊名：Environmental Science & Technology
• 出版年：2009
• 出版时间：February 1, 2009
• 年：2009
• 卷：43
• 期：3
• 页码：604-609
• 全文大小：221K
• 年卷期：v.43,no.3(February 1, 2009)
• ISSN：1520-5851

文摘

Anthropogenic emissions of atmospheric nitrogen have increased over the last century, but the monitoring of nitrous oxide concentrations is only recent. Can trees from temperate regions be used to infer past changes in nitrogen cycles? To consider this question, we investigate nitrogen isotope (δ¹⁵N) ring series from pine and beech trees near Montréal, and beech specimens of Georgian Bay Islands. The δ¹⁵N values show coherent intertree and interspecies trends, independent of the sapwood−heartwood transition zones, implying that these results reflect local environmental conditions. At both sites, short-term isotopic fluctuations correlate directly with precipitation and inversely with temperature. Long-term isotope decreases of 1.5 to 2‰ suggest progressive changes in soil nitrogen after 1951. In Georgian Bay, an additional important change is inferred on the basis of a 1.5‰ increase initiated after 1971. At both sites, long-term series correlate with a proxy for NO_x emissions. We propose that the contrasted long-term δ¹⁵N changes of Montreal and Georgian Bay reflect deposition of NO_x emissions from cars and coal-power plants, with higher proportions from coal burning in Georgian Bay. This research suggests that tree-ring δ¹⁵N series may record both, regional climatic conditions and anthropogenic perturbations of N cycles.