Warm season precipitation signal in δ 2 H values of wood lignin methoxyl groups from high elevation larch trees in Switzerland

Rationale In this study, we tested stable hydrogen isotope ratios of wood lignin methoxyl groups ( δ 2 H methoxyl values) as a palaeoclimate proxy in dendrochronology. This is a quite new method in the field of dendrochronology and the sample preparation is much simpler than the methods used before to measure δ 2 H values from wood. Methods We measured δ 2 H methoxyl values in high elevation larch trees ( Larix decidua Mill.) from Simplon Valley (southern Switzerland). Thirty‐seven larch trees were sampled and five individuals analysed for their δ 2 H methoxyl values at annual (1971–2009) and pentadal resolution (1746–2009). The δ 2 H methoxyl values were measured as CH 3 I released upon treatment of the dried wood samples with hydroiodic acid. 10–90 μL from the head‐space were injected into the gas chromatography/high‐temperature conversion/isotope ratio mass spectrometry (GC/HTC‐IRMS) system. Results Testing the climate response of the δ 2 H methoxyl values, the annually resolved series show a positive correlation of r = 0.60 with June/July precipitation. The pentadally resolved δ 2 H methoxyl series do not show any significant correlation to climate parameters. Conclusions Increased precipitation during June and July, which are on average warm and relatively dry months, results in higher δ 2 H values of the xylem water and, therefore, higher δ 2 H values in the lignin methoxyl groups. Therefore, we suggest that δ 2 H methoxyl values of high elevation larch trees might serve as a summer precipitation proxy.