Abstract For dendroclimatological Blue Intensity (BI) studies based on earlywood (EW) or latewood (LW) information, a demarcation between the two is necessary, which can be difficult to establish for species where the transition is subtle. Often, a percental value k is used that calculates an EW/LW boundary value for each tree ring individually based on the difference between maximum and minimum absorption. Several laboratories and authors have used different values for k (e.g. k = 30 % or k = 50 %), while wood anatomical and visual studies suggest that k is on the order of 80 %. Here, we test how different settings of k, and thus different definitions of the EW and LW proportions of a tree ring, influence the dendroclimatic potential of derived time series. To this end, we correlate instrumental temperature measurements with tree ring chronologies that are based on EW and LW information (e.g. EW absorption (EWBI), LW absorption (LWBI)), where the EW/LW proportion is varied by setting different values for k. The tree ring samples utilized are 30 cores of spruce (Picea abies) trees from a high-elevated site (ca. 1700 m a.s.l.) in the northern Alps, Austria. Overall, we achieve high correlations between temperature data and our tree ring chronologies. Regarding the stability of the climate signal under different k values, the results show that absorption intensity based parameters (ΔBI, EWBI, LWBI) are only mildly influenced by different settings of k, while width based parameters (EW width, LW width) show a larger dependence on k. LW width, for instance, was stronger correlated with temperature, the smaller the LW was chosen (and thus the higher k was set). Based on our results and the wood anatomical definition of the EW/LW boundary, we suggest that k = 80 % may be a good choice for future studies. However, since this is only a case study from one site, careful screening of the respective data set regarding an appropriate k value must accompany each dendroclimatological study.

中文翻译：

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测试不同早材/晚材划界以建立蓝色强度数据：基于高山云杉样本的案例研究

摘要 对于基于早材 (EW) 或晚材 (LW) 信息的树木气候学蓝色强度 (BI) 研究，两者之间的分界是必要的，这对于过渡微妙的物种可能难以确定。通常，使用百分比值 k 根据最大​​和最小吸收之间的差异单独计算每个树木年轮的 EW/LW 边界值。几个实验室和作者使用了不同的 k 值（例如 k = 30 % 或 k = 50 %），而木材解剖和视觉研究表明 k 约为 80 %。在这里，我们测试了 k 的不同设置以及树轮的 EW 和 LW 比例的不同定义如何影响派生时间序列的树状气候潜力。为此，我们将仪器温度测量与基于 EW 和 LW 信息（例如 EW 吸收 (EWBI)、LW 吸收 (LWBI)）的树木年轮年表相关联，其中 EW/LW 比例通过设置不同的 k 值而变化。使用的年轮样本是来自奥地利阿尔卑斯山北部高海拔地区（海拔 1700 米）的 30 颗云杉（Picea abies）树芯。总体而言，我们实现了温度数据和我们的树木年轮年表之间的高度相关性。关于不同 k 值下气候信号的稳定性，结果表明基于吸收强度的参数（ΔBI、EWBI、LWBI）仅受不同 k 设置的轻微影响，而基于宽度的参数（EW 宽度、LW 宽度）显示对 k 的依赖性更大。例如，LW 宽度与温度的相关性更强，选择的 LW 越小（因此设置的 k 越高）。根据我们的结果和 EW/LW 边界的木材解剖学定义，我们建议 k = 80 % 可能是未来研究的不错选择。然而，由于这只是来自一个站点的案例研究，因此每次树木气候学研究都必须仔细筛选有关适当 k 值的相应数据集。