Assessment of stable isotope time series from Baobab trees (Adansonia digitata) as a high-resolution climate archive for (semi-)arid Africa

根据IPCC的数据，在本世纪，整个非洲很可能比全球平均水平更温暖。特别是（半）干旱地区面临着经历特别高的变暖和可能的灾难性干旱的危险。预测气候变化对这些区域的影响需要有高时空分辨率的过去气候条件信息。欧亚大陆和北美洲有大型的多代理数据网络，但非洲大陆却严重缺乏跨区域的高时间分辨率代理数据。本研究的目的是评估和建立非洲猴面包树，猴面包树，作为一个新的气候档案（半）干旱非洲。猴面包树广泛分布在整个（半）干旱的非洲和14 C测年显示，个人达到年龄高达2000年。我们打算在纳米比亚、博茨瓦纳、津巴布韦、莫桑比克和南非北方沿沿着两个样带采集大量猴面包树的核心样本。目的是为每个取样地点提供复制良好的树木年轮宽度和稳定同位素（d13 C、d18 O）年表，通过监测和气候数据对其进行校准和核实，并重建决定过去干旱期频率和严重程度的降水状况变化。除此之外，我们希望获得更多的信息猴面包树的气候响应和他们的适应性变化的水的可用性和大气中的CO2浓度（内在的水利用效率，iWUE）在人类世从稳定同位素分析（d13 C，d18 O）。由于树木年轮气候学的基本目的是更好地了解树木生长的季节变化、气候信号以及稳定同位素从大气、土壤和树叶转移到树木年轮的木材中，因此将进行全面的树木年轮生态监测。2012年10月已经建立了一个监测点，以便为项目提供三个植被期的观测数据。计划与南非伙伴合作，将监测范围扩大到更多的树木。通过长期的调查，我们的目标是更好地了解生理基础不同的猴面包树木材形成和稳定同位素分馏由于环境的影响。在本项目中，我们将：（任务1）研究气候信号和猴面包树树木系统中从大气通过土壤和树叶到树木年轮的稳定同位素转移;（任务2）评估猴面包树在生长、内在水利用效率（d13 C）和树木年轮氧的稳定同位素比率方面的气候响应;（任务3）建立良好复制的代理数据系列（200年）的树木生长，d13 C和d18 O在6个地点沿着两个横断面横跨南部非洲;（任务4）以次十年时间分辨率重建至少一个地点上千年的降水状况和过去的特大干旱。

According to the IPCC all of Africa is very likely to warm more than global average during this century. Especially (semi-)arid regions are endangered to experience particular high warming and possibly catastrophic droughts. The prediction of the climate change impact on these regions requires information about the past climate conditions in high temporal and spatial resolution. Large networks of multi-proxy data exist for Eurasia and North America, but there is a massive lack of transregional highly time resolved proxy data for the African continent. The aim of this study is to evaluate and establish the African baobab, Adansonia digitata L., as a new climate archive for (semi-)arid Africa. Baobab trees are widely distributed throughout (semi)-arid Africa and 14C-dating has revealed individuals reaching ages of up to 2000 years. We intent to core-sample numerous baobabs along two transects over southern Africa with sampling locations in Namibia, Botswana, Zimbabwe, Mozambique, and northern South Africa. The objective is to provide well-replicated tree-ring width and stable isotope (d13C, d18O) chronologies for each sampling location, to calibrate and verify them by monitoring- and climate-data and to reconstruct changes in precipitation regimes governing frequency and severity of past drought periods. In addition to this, we expect to obtain additional information about the climate response of baobabs and their adaptability to changes in water availability and atmospheric CO2 concentration (intrinsic water use efficiency, iWUE) during the Anthropocene from stable isotope analyses (d13C, d18O). As it is fundamental for dendroclimatology to better understand seasonal changes in tree growth, climate signal and stable isotope transfer from atmosphere, soil and leaves into the wood of tree-rings, comprehensive dendroecological monitoring will be undertaken. A monitoring site has already been setup in October 2012 so that observations for three vegetation periods will already be available for the project. In cooperation with South African partners it is planned to extend the monitoring to additional trees. By long-term investigations we are targeting a better understanding of the physiology that underlies varying baobab wood formation and stable isotope fractionation due to environmental impacts. In this project we shall: (task-1) study climate signal and stable isotope transfer in the baobab arboreal system from atmosphere through soil and leaves into the wood of tree rings; (task-2) assess the climate response of baobabs in terms of growth, intrinsic water-use efficiency (d13C) and tree-ring stable isotope ratios of oxygen; (task-3) establish well replicated proxy data series (for 200 years) of tree growth, d13C and d18O at 6 sites along two transects across southern Africa; (task-4) reconstruct precipitation regimes and past mega-droughts for the last Millennium for at least one site in sub-decadal time resolution.