Abstract We explore the potential of the delta blue intensity (DBI) parameter as a proxy of past summer temperatures using a well replicated (85 trees) chronology of Pinus uncinata from upper treeline in the Spanish Pyrenees. Principal component analysis, correlation response function analysis and Superposed Epoch Analysis show definitively that the DBI data are indistinguishable to other MXD datasets in the region and that DBI expresses a similarly “pure” time-stable climate signal as MXD when compared to their RW counterparts. Calibration r2 values > 0.5 are attainable depending on period used. The signal strength of DBI data is weaker than MXD and behave more like RW data with ca. 19 trees being needed to attain an EPS value > 0.85. However, as the generation of DBI data is cheaper than MXD, this limitation is not deemed to be a serious issue. This pilot study suggests that robust reconstructions of past summer temperatures could be gained using DBI data at a much-reduced cost than relying on MXD. Future dendroclimatic efforts in the region therefore should focus on the measurement of this parameter and the expansion of the pinus ring-density network.

中文翻译：

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Delta Blue 强度与最大密度：在比利牛斯山使用松树的案例研究

摘要 我们使用来自西班牙比利牛斯山脉上部树线的经过充分复制（85 棵树）的松木年表，探索了蓝色强度 (DBI) 参数作为过去夏季温度代理的潜力。主成分分析、相关响应函数分析和叠加历元分析明确表明，DBI 数据与该地区的其他 MXD 数据集无法区分，并且与 RW 对应数据相比，DBI 表达了与 MXD 类似的“纯”时间稳定气候信号。校准 r2 值 > 0.5 取决于使用的时间段。DBI 数据的信号强度比 MXD 弱，表现得更像 RW 数据。需要 19 棵树才能达到 EPS 值 > 0.85。但是，由于 DBI 数据的生成比 MXD 便宜，这种限制不被认为是一个严重的问题。这项试点研究表明，使用 DBI 数据可以获得对过去夏季温度的稳健重建，其成本比依赖 MXD 低得多。因此，该地区未来的树木气候工作应侧重于该参数的测量和松树环密度网络的扩展。