Forests in the western United States are being subject to more frequent and severe drought events as the climate warms. The 2012–2015 California drought is a recent example, whereby drought stress was exacerbated by a landscape-scale outbreak of western pine beetle (Dendroctonus brevicomis) and resulted in widespread mortality of dominant canopy species including ponderosa pine (Pinus ponderosa). In this study, we compared pairs of large surviving and beetle-killed ponderosa pines following the California drought in the southern Sierra Nevadas to evaluate physiological characteristics related to survival. Inter-annual growth rates and tree-ring stable isotopes (∆¹³C and δ¹⁸O) were utilized to compare severity of drought stress and climate sensitivity in ponderosa pines that survived and those that were killed by western pine beetle. Compared to beetle-killed trees, surviving trees had higher growth rates and grew in plots with lower ponderosa pine basal area. However, there were no detectable differences in tree-ring ∆¹³C, δ¹⁸O, or stable isotope sensitivity to drought-related meteorological variables. These results indicate that differences in severity of drought stress had little influence on local, inter-tree differences in growth rate and survival of large ponderosa pines during this drought event. Many previous studies have shown that large trees are more likely to be attacked and killed by bark beetles compared to small trees. Our results further suggest that among large ponderosa pines, those that were more resistant to drought stress and bark beetle attacks were in the upper echelon of growth rates among trees within a stand and across the landscape.

随着气候变暖，美国西部的森林正遭受更频繁和严重的干旱事件。最近的一个例子是2012-2015年加利福尼亚州的干旱，西部松树甲虫（Dendroctonus brevicomis）的景观规模爆发加剧了干旱压力，导致包括黄松（Pinus tankerosa）在内的优势冠层物种广泛死亡。在这项研究中，我们比较了内华达山脉南部加利福尼亚干旱之后成对的大型存活和被甲虫杀死的黄松，以评估与存活有关的生理特征。间年增长率和年轮稳定同位素（Δ ¹³ C和δ ¹⁸O）用于比较存活的和被西部松甲虫杀死的美国黄松的干旱胁迫严重程度和气候敏感性。与杀死甲虫的树木相比，幸存的树木具有较高的生长速度，并在黄松松基面积较低的地块中生长。然而，有在树轮Δ没有可检测到的差异¹³ C，δ ¹⁸O，或对干旱相关的气象变量具有稳定的同位素敏感性。这些结果表明，在干旱事件中，干旱胁迫的严重程度差异对大型美国黄松的生长速度和存活率的局部树间差异影响很小。以前的许多研究表明，与小树相比，大树更容易被树皮甲虫袭击和杀死。我们的结果进一步表明，在大型美国黄松中，对干旱胁迫和树皮甲虫侵袭更具抵抗力的松树位于林分中和整个景观中树木生长速率的上梯级。