High-resolution 14C bomb peak dating and climate response analyses of subseasonal stable isotope signals in wood of the African baobab – a case study from Oman
High-resolution 14C bomb peak dating and climate response analyses of subseasonal stable isotope signals in wood of the African baobab – a case study from Oman
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DOI：
10.5194/bg-2019-325
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发表时间：
2019-08
期刊：
影响因子：
4.9
通讯作者：
Franziska Slotta;L. Wacker;F. Riedel;K. Heussner;K. Hartmann;G. Helle
中科院分区：
文献类型：
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作者：
Franziska Slotta;L. Wacker;F. Riedel;K. Heussner;K. Hartmann;G. Helle
抽象的。非洲猴面包树，猴面包树，分布范围广，寿命长达千年，具有巨大的古气候学潜力。然而，由于其独特的，薄壁组织占主导地位的茎解剖学，树木气候学的方法受到阻碍的日期不确定性。在这里，安全日期的时间序列的年度木材增量增长和环内稳定同位素的碳和氧的纤维素的猴面包树从阿曼覆盖1941年至2005年建立和测试水文气候变异的关系。使用高分辨率14 C测量的原子弹峰值（ABP）精确测年证实了猴面包树年轮的年度特征。发现树轮纤维素的F14 C值比ABP周围相应的大气CO2低8.8%，这与δ 13 C系列的相当大的自相关性相结合，表明前一年的碳有助于环内木材样品的平均年龄。F14 C的终端薄壁组织带，标志着树轮的边界，被发现是相当年轻的比他们相应的树轮，表明薄壁组织是活了很多年，可能经历细胞分裂和结构重组，并有助于二次生长。与δ 13 C时间序列相反，尽管这种茎多汁树种具有巨大的储水潜力，但在树轮纤维素的δ 18 O序列中没有发现显著的自相关性。年轮宽度和稳定同位素比值的年与年的变化表明，径向茎生长和木材纤维素的地球化学受水文气候波动的影响。特别是，δ 18 O被发现是一个很好的气候指标，其次是树轮宽度和δ 13 C。树轮宽度和环内δ 18 Omin与5月季风前至9月/10月季风期结束的降水量有较好的相关性。δ 13 C和δ 18 O的年内稳定同位素变化过程非常相似。季风雨特别低的年份，反映了增加的稳定同位素值在年内课程的中段。不同的模式与低的亚季节同位素值似乎指示多年的暴雨事件，从季风前气旋。季风后气旋的降雨事件也可能被记录下来;然而，只有2年的观测阻止了更确定的评估。
Abstract. The African baobab, Adansonia digitata L., has great paleoclimatological potential because of its wide distributional range and millennial length life span. However, dendroclimatological approaches are hampered by dating uncertainties due to its unique, parenchyma-dominated stem anatomy. Here, securely dated time series of annual wood increment growth and intra-ring stable isotopes of carbon and oxygen of cellulose for a baobab tree from Oman covering 1941 to 2005 were established and tested for relationships to hydroclimate variability. Precise dating with the atomic bomb peak (ABP) using highly resolved 14C measurements confirmed the annual character of the baobab's growth rings. F14C values of tree-ring cellulose were found up to 8.8 % lower than in the corresponding atmospheric CO2 for the period around the ABP, which in conjunction with a considerable autocorrelation of the δ13C series points to the incorporation of previous year's carbon contributing to the average age of intra-ring wood samples. F14C of terminal parenchyma bands, marking the tree-ring boundaries, were found to be considerably younger than their corresponding tree ring, indicating that parenchyma tissue is alive for many years, probably undergoing cell division and structural reorganization and contributing to secondary growth. In contrast to the δ13C time series, no significant autocorrelation was found in the δ18O series of tree-ring cellulose despite the enormous water storage potential of this stem-succulent tree species. Year-to-year variability in tree-ring width and stable isotope ratios revealed radial stem growth and the geochemistry of wood cellulose are influenced by fluctuations in the hydroclimate. In particular, δ18O was found to be a good climate proxy, followed by tree-ring width and δ13C. Tree-ring width and intra-ring δ18Omin correlated well with each other and with precipitation amount for the period from pre-monsoon May to the end of the monsoon season in September/October. Intra-annual stable isotope courses were found to be rather similar for both δ13C and δ18O. Years with particularly low monsoon rain were reflected by increased stable isotope values in the mid-section of intra-annual courses. Distinct patterns with low subseasonal isotope values seem indicative for years with heavy rainfall events from pre-monsoonal cyclones. Rain events from post-monsoonal cyclones may also be recorded; however, only 2 years of observation prevented a more conclusive evaluation.