Temperature reconstructions for the last 140 years at Hohenpeißenberg using stable isotopes of wood lignin methoxyl groups

树木年轮是广泛使用的气候档案，提供关于百年到千年时间尺度的年度决议。木质素是一种主要的木材成分(高达三分之一)，含有高达20%的甲氧基。最近有人提出，这些木素甲氧基是研究年轮等气候档案中稳定氢同位素的理想靶基。事实上，木材木素甲氧基的稳定氢同位素比率已被证明反映了降水的稳定氢同位素比率，而降水的稳定氢同位素比率主要受温度等气候因素的控制。此外，我们最近研究了在欧洲南北方向约3500公里的样带上采集的不同树种年轮木素甲氧基的稳定氢同位素，年平均温度(MAT)在-4到+17℃之间。我们发现木材木素甲氧基的稳定氢同位素与木材木质素甲氧基的稳定氢同位素之间存在很强的线性关系。我们利用这种关系从随机采集的木材样本中预测了MAT，并发现在全球范围内预测的中纬度地区的MAT与观测到的MAT大致一致。因此，我们认为木素甲氧基稳定氢同位素可以作为重建全新世中纬度温度的古温度计。然而，现在需要进一步的校准研究，以更准确地获得温度对较低MAT范围内木素甲氧基稳定氢同位素的影响。该项目的目标是使用欧洲山毛榉木质素甲氧基的高分辨率稳定氢同位素年代学重建德国霍恩佩恩贝格过去140年的年平均温度。霍恩佩恩贝格被认为是一个理想的采样点，因为附近是德国湿地气象站，提供气候数据的连续记录(完整记录可以追溯到公元1782年)。自有记录以来，霍恩佩贝恩贝格的年平均温度在4.5至8.7摄氏度之间有很大的变化，并与降水的稳定氢同位素值(自1971年以来监测)有显著的相关性。在拟议的项目中，我们将调查树龄至少为120至140年的树木。我们将抽样15至20棵欧洲山毛榉(每棵树三个核)，并测量树轮宽度(TRW)，以验证交叉定年和评估欧洲山毛榉在该地区生长的气候控制。对于稳定的氢同位素测量，将选择三棵单独的欧洲山毛榉树，以避免潜在的特定地点的影响。利用获得的样本，应该可以评估德国南部气象站记录附近的潜在干旱(TRW)和温度(稳定氢同位素)对木材形成的影响。因此，这项研究可能会为古气候学领域的进一步应用提供有价值的温度校准。

Tree rings are widely used climate archives providing annual resolutions on centennial to millennial timescales. Lignin is a major wood component (up to one third) and contains up to 20% methoxyl groups. Recently it was suggested that these lignin methoxyl groups were an ideal target moiety for the investigation of stable hydrogen isotopes in climate archives such as tree rings. Indeed the stable hydrogen isotope ratio of wood lignin methoxyl groups has been shown to mirror the stable hydrogen isotope ratio of precipitation which is mainly controlled by climatic factors such as temperature. Moreover, we recently investigated stable hydrogen isotopes of lignin methoxyl groups of tree rings from various species collected along a ~3500 km north-south transect across Europe with mean annual temperatures (MAT) ranging from -4 to +17°C. We found a strong linar relationship between the MAT and stable hydrogen isotopes of wood lignin methoxyl groups. We used this relationship to predict MAT from randomly collected wood samples and found general agreement between predicted and observed MATs for the mid-latitudes on a global scale. Thus we suggested that stable hydrogen isotopes of lignin methoxyl groups might be used as a paleothermometer to reconstruct mid-latitude temperatures of the Holocene. However, further calibration studies are now required to more accurately access the influence of temperature on the stable hydrogen isotopes of lignin methoxyl groups for a lower range of MAT. The goal of this project is to reconstruct mean annual temperatures at Hohenpeißenberg (Germany) for the last 140 years using a high resolution stable hydrogen isotope chronology of lignin methoxyl groups in European beech trees (Fagus sylvatica). Hohenpeißenberg is considered an ideal sampling site since nearby is a weather station of the Deutsche Wetterdienst which provides a continuous record of climate data (full record dates back to 1782 AD). Since records began, the mean annual temperatures at Hohenpeißenberg show substantial variations ranging from 4.5 to 8.7°C and also show a significant correlation with stable hydrogen isotope values of precipitation (monitored since 1971). In the proposed project we will investigate trees with a minimum age of 120 to 140 years. We will sample 15 to 20 European beech trees (three cores per tree) and measure the tree ring width (TRW) to validate cross-dating and assess the climate controls of European beech growth in the region. For stable hydrogen isotope measurements three individual European beech trees will be selected to avoid potential site-specific influences. With the obtained samples it should be possible to assess the potential drought (TRW) and temperature influences (stable hydrogen isotopes) on wood formation in the close vicinity of weather station records from southern Germany. Consequently, this study would likely provide a valuable temperature calibration for further applications in the field of paleoclimatology.