Long-term trends in European tree growth over the past 1000 years - an interspecies comparison

每年解决和绝对定年的陆地气候代理，如树木年轮构成的基础上，高分辨率的古气候学涵盖了过去的千年。在欧洲，从高海拔和高纬度地区的树木年轮推断出的温度变化过去和现在都在进行深入研究。相反，低海拔地区（<1000 m a.s.l.）尽管水文气候变异性（即降水和干旱）是目前对过去和未来气候变化进行评估的一个关键因素，但气候变化的概念最近才受到重视。潜在的强迫因素，幅度和频率的长期（即几十年到百年）的增长趋势，这是必不可少的重建水文气候变率的全部范围，只是研究，尚未完全understood.在拟议的项目中，大规模的多物种比较欧洲各地的长期增长趋势，跨越上一个千年，将进行第一次。在过去的几十年里，从欧洲低海拔和降水敏感的树种，如橡树，山毛榉，桤木，白蜡，榆树，冷杉，松树和云杉的树木年轮测量已收集到历史和考古木材，并与现在的材料从生活树木产生多个物种年表，跨越过去的千年。这个独特的数据集超过60.000树木年轮测量，包括生态和经济上最重要的欧洲树种是通过一个密集和活跃的合作伙伴网络提供的。拟议项目的目的是更好地了解树木生长低频趋势的时空变化，并确定这些重要的驱动因素（即气候和/或火山、CO2或太阳强迫）影响欧洲树木生长。所采用的方法将涉及最近开发的标准化方法、趋势和频谱分析以及不同的过滤技术;所有这些都经过优化，以检测和描述树木年轮年表气候信号的低频变化。提取的长期增长趋势将在欧洲不同地区的物种内和物种间水平进行比较。为了确定十年至百年趋势的驱动因素，从其他代理档案中获得的时间序列（例如沉积物）将测试其与树木生长的一致性，以及各种气候参数的影响，包括水流和地下水变化，以及强迫异常。树木生长的低频趋势及其根本原因将改善气候重建、模型模拟和大陆到全球范围碳循环长期变化的量化。

Annually resolved and absolutely dated terrestrial climate proxies such as tree rings constitute the basis of high-resolution paleoclimatology covering the past millennia. For Europe, temperature variability inferred from tree rings from high altitudes and latitudes was and still is intensively studied. Conversely, research of precipitation sensitive tree-ring records from low elevation sites (<1000 m a.s.l.) has only recently gained attraction, although hydroclimate variability (i.e. precipitation and drought) is a crucial element in the ongoing assessment of past and future climate change. Potential forcing factors, the amplitude and frequency of long-term (i.e. multi-decadal to centennial) growth trends, which are essential to reconstruct the full range of hydroclimate variability, are merely studied and not yet fully understood.In the proposed project, a large-scale multi-species comparison of long-term growth trends across Europe, spanning the last millennium, will be conducted for the first time. During the past decades tree-ring measurements from low-elevation and precipitation sensitive tree species in Europe such as oak, beech, alder, ash, elm, fir, pine and spruce have been collected from historical and archaeological timbers, and linked to the present with material from living trees to produce multiple species chronologies that span the last millennium. This unique data set of over 60.000 tree-ring measurements, including the most ecologically and economically important European tree species is available through a dense and active network of collaboration partners.The aim of the proposed project is to better understand the spatiotemporal variability of low frequency trends in tree growth and identify those significant drivers (i.e. climate and/or volcanic, CO2 or solar forcing) affecting tree growth over Europe. Methods applied will involve recently developed standardization methods, trend and spectral analyses, as well as different filtering techniques; all optimized to detect and describe low-frequency variations in the climate signal of tree-ring chronologies. The extracted long-term growth trends will be compared across different regions within Europe at the intra- and inter-species levels. To identify drivers of decadal to centennial trends, time series derived from other proxy archives (e.g. sediments) will be tested for their coherency with tree growth, as well as the influence of various climate parameters including stream flow and groundwater changes, and forcing anomalies.New findings gained in the proposed project of climate forced, low-frequency trends in tree growth and their underlying causes will improve climate reconstructions, model simulations and the quantification of long-term changes in the carbon cycle at continental to global scale.