Riechelmann Dana F C, Greule Markus, Siegwolf Rolf T W, Anhäuser Tobias, Esper Jan, Keppler Frank
Institute of Geography, Johannes Gutenberg-University Mainz, Johann-Joachim-Becher-Weg 21, 55128, Mainz, Germany.
Institute of Geosciences, Johannes Gutenberg-University Mainz, Johann-Joachim-Becher-Weg 21, 55128, Mainz, Germany.
Rapid Commun Mass Spectrom. 2017 Oct 15;31(19):1589-1598. doi: 10.1002/rcm.7938.
In this study, we tested stable hydrogen isotope ratios of wood lignin methoxyl groups (δ H 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 H values from wood.
We measured δ H 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 H values at annual (1971-2009) and pentadal resolution (1746-2009). The δ H values were measured as CH 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.
Testing the climate response of the δ H values, the annually resolved series show a positive correlation of r = 0.60 with June/July precipitation. The pentadally resolved δ H series do not show any significant correlation to climate parameters.
Increased precipitation during June and July, which are on average warm and relatively dry months, results in higher δ H values of the xylem water and, therefore, higher δ H values in the lignin methoxyl groups. Therefore, we suggest that δ H values of high elevation larch trees might serve as a summer precipitation proxy.
在本研究中，我们测试了树木木质素甲氧基的稳定氢同位素比率（δH值），将其作为树木年代学中的古气候替代指标。这在树木年代学领域是一种相当新的方法，且样品制备比以前用于测量木材δH值的方法要简单得多。
我们测量了来自瑞士南部辛普朗山谷高海拔落叶松（欧洲落叶松）的δH值。采集了37棵落叶松样本，并对其中5棵个体在年度（1971 - 2009年）和五年分辨率（1746 - 2009年）下分析其δH值。δH值通过用氢碘酸处理干燥木材样本后释放的CHI进行测量。从顶空抽取10 - 90μL注入气相色谱/高温转换/同位素比率质谱（GC/HTC - IRMS）系统。
测试δH值的气候响应时，年度分辨率序列与6月/7月降水量呈正相关，r = 0.60。五年分辨率的δH序列与气候参数未显示出任何显著相关性。
6月和7月平均温暖且相对干燥的月份降水量增加，导致木质部水的δH值升高，进而使木质素甲氧基中的δH值升高。因此，我们认为高海拔落叶松的δH值可能可作为夏季降水量的替代指标。
