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树木年轮稳定同位素的合并测量与单独测量。

Pooled versus separate measurements of tree-ring stable isotopes.

机构信息

Universitat de Barcelona, Departament d'Ecologia, Diagonal 645, 08028, Barcelona, Spain.

出版信息

Sci Total Environ. 2011 May 1;409(11):2244-51. doi: 10.1016/j.scitotenv.2011.02.010. Epub 2011 Mar 12.

Abstract

δ(13)C and δ(18)O of tree rings contain time integrated information about the environmental conditions weighted by seasonal growth dynamics and are well established as sources of palaeoclimatic and ecophysiological data. Annually resolved isotope chronologies are frequently produced by pooling dated growth rings from several trees prior to the isotopic analyses. This procedure has the advantage of saving time and resources, but precludes from defining the isotopic error or statistical uncertainty related to the inter-tree variability. Up to now only a few studies have compared isotope series from pooled tree rings with isotopic measurements from individual trees. We tested whether or not the δ(13)C and the δ(18)O chronologies derived from pooled and from individual tree rings display significant differences at two locations from the Iberian Peninsula to assess advantages and constraints of both methodologies. The comparisons along the period 1900-2003 reveal a good agreement between pooled chronologies and the two mean master series which were created by averaging raw individual values (Mean) or by generating a mass calibrated mean (MassC). In most of the cases, pooled chronologies show high synchronicity with averaged individual samples at interannual scale but some differences also show up especially when comparing δ(18)O decadal to multi-decadal variations. Moreover, differences in the first order autocorrelation among individuals may be obscured by pooling strategies. The lack of replication of pooled chronologies prevents detection of a bias due to a higher mass contribution of one sample but uncertainties associated with the analytical process itself, as sample inhomogeneity, seems to account for the observed differences.

摘要

树木年轮的 δ(13)C 和 δ(18)O 包含了环境条件的时间综合信息,这些信息是通过季节性生长动态加权得到的,它们是古气候和生态生理学数据的良好来源。在进行同位素分析之前,通常通过汇集来自多棵树的有年代的生长环来制作每年分辨率的同位素年表。这种方法具有节省时间和资源的优点,但无法确定与树木间变异性相关的同位素误差或统计不确定性。到目前为止,只有少数研究比较了来自汇集树木年轮的同位素系列与来自单个树木的同位素测量结果。我们检验了从汇集和单个树木年轮中得出的 δ(13)C 和 δ(18)O 年表在伊比利亚半岛的两个地点是否存在显著差异,以评估这两种方法的优缺点。在 1900 年至 2003 年期间的比较表明,汇集年表与通过平均原始个体值(Mean)或通过生成质量校准平均值(MassC)生成的两个主系列之间存在良好的一致性。在大多数情况下,汇集年表在年际尺度上与平均个体样本具有高度的同步性,但在比较 δ(18)O 十年到多十年的变化时,也会出现一些差异。此外,个体之间的一阶自相关差异可能会被汇集策略所掩盖。由于一个样本的质量贡献更高而导致的汇集年表的复制缺乏,会阻止检测到偏差,但与分析过程本身相关的不确定性,如样本非均一性,似乎可以解释观察到的差异。

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