Abstract Here we examine climatic influences on inter-annual variation in latewood tree growth (i.e. ring-width indices, RWILW) and stable-carbon isotope discrimination (Δ13CLW) from 1950 to 2013 at two SNOTEL snowpack monitoring sites in the Oregon Cascade Mountains. Douglas-fir and mountain hemlock trees were sampled at the lower and upper elevation sites where annual peak snow water equivalent (SWE) averaged 467 and 1128 mm, respectively. RWILW chronologies were poorly correlated among sites/species (r = 0.23, P = 0.063) and neither exhibited strong correlations with monthly or seasonal climate variables. By contrast, Δ13CLW chronologies were significantly correlated (r = 0.69, P < 0.001) and exhibited stronger climate responses. Multiple regression analyses identified summertime maximum temperature (Tmax) and/or vapor pressure deficit (VPD) as the primary drivers of Δ13CLW. Secondary influences included summertime precipitation, specific humidity, cloud cover, and SWE from the previous fall and winter. Overall, our findings suggest that Cascade mixed conifer forests will become increasingly drought stressed as rising temperatures cause progressively diminished snowpacks. Moreover, our Δ13CLW records also provide a proof of concept showing strong potential to expand summertime Tmax reconstructions to other snowy, montane locations.

中文翻译：

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来自俄勒冈州西部喀斯喀特山脉的年轮碳同位素记录主要记录夏季最高气温

摘要 在这里，我们研究了 1950 年至 2013 年俄勒冈州喀斯喀特山脉的两个 SNOTEL 积雪监测点的气候对晚材树生长年际变化（即环宽指数，RWILW）和稳定碳同位素鉴别（Δ13CLW）的影响。在年峰值雪水当量 (SWE) 平均分别为 467 和 1128 毫米的低海拔和高海拔地点对花旗松和山地铁杉树进行了采样。RWILW 年表在地点/物种之间的相关性较差（r = 0.23，P = 0.063），并且与月度或季节气候变量均未表现出强相关性。相比之下，Δ13CLW 年表显着相关（r = 0.69，P < 0.001）并表现出更强的气候响应。多元回归分析确定夏季最高温度 (Tmax) 和/或蒸气压不足 (VPD) 是 Δ13CLW 的主要驱动因素。次要影响包括夏季降水、比湿度、云量和前一个秋季和冬季的 SWE。总体而言，我们的研究结果表明，随着气温升高导致积雪逐渐减少，喀斯喀特混交针叶林将面临越来越严重的干旱压力。此外，我们的 Δ13CLW 记录还提供了一个概念证明，显示了将夏季 Tmax 重建扩展到其他多雪的山地位置的巨大潜力。我们的研究结果表明，随着气温升高导致积雪逐渐减少，喀斯喀特混交针叶林将面临越来越严重的干旱压力。此外，我们的 Δ13CLW 记录还提供了一个概念证明，显示了将夏季 Tmax 重建扩展到其他多雪的山地位置的巨大潜力。我们的研究结果表明，随着气温升高导致积雪逐渐减少，喀斯喀特混交针叶林将面临越来越严重的干旱压力。此外，我们的 Δ13CLW 记录还提供了一个概念证明，显示了将夏季 Tmax 重建扩展到其他多雪的山地位置的巨大潜力。