Climate signals in δ13C of wood lignin methoxyl groups from high-elevation larch trees

In this study, a barely used method to measure delta C-13 values from lignin methoxyl groups (delta C-13(methpxyl)) of tree rings is applied to high alpine larch trees to test their potential as a climate proxy. Thirty-seven larch trees (Larix decidua Mill.) were sampled at a tree line site near Simplon Village in the Valais/Switzerland. Samples were used to measure tree-ring width, and from five individuals, delta C-13(methpxyl) was determined at annual resolution from 1971 to 2009, and at pentadal resolution from 1747 to 2009. The physiological tree responses to increasing atmospheric CO2 concentration since 1850 and the corresponding decrease in delta C-13 (Suess effect) were corrected using a range of published discrimination factors and approaches. One of these approaches considers a flexible correction factor, which minimizes the residuals with target climate data. Testing the response of the new delta C-13(methpxyl) to climate revealed significant correlations with June to August temperatures, ranging from r = 0.56 to 0.75 for annually and from r = 0.41 to 0.87 for pentadally resolved data depending on the correction methods. Tree-ring width also shows significant correlations with June to August temperature. These results demonstrate the potential of delta C-13(methpxyl) to serve as a summer temperature proxy in high-elevation alpine environments. (C) 2016 Elsevier B.V. All rights reserved.