Ecology. 2014 Apr;95(4):930-9. doi: 10.1890/13-0230.1.
This study examines influences of climate variability on spruce beetle (Dendroctonus rufipennis) outbreak across northwestern Colorado during the period 1650 2011 CE. Periods of broad-scale outbreak reconstructed using documentary records and tree rings were dated to 1843-1860, 1882-1889, 1931-1957, and 2004-2010. Periods of outbreak were compared with seasonal temperature, precipitation, vapor pressure deficit (VPD), the Palmer Drought Severity Index (PDSI), and indices of ocean-atmosphere oscillation that include the El Niño Southern Oscillation (ENSO), Pacific Decadal Oscillation (PDO), and Atlantic Multidecadal Oscillation (AMO). Classification trees showed that outbreaks can be predicted most successfully from above average annual AMO values and above average summer VPD values, indicators of drought across Colorado. Notably, we find that spruce beetle outbreaks appear to be predicted best by interannual to multidecadal variability in drought, not by temperature alone. This finding may imply that spruce beetle outbreaks are triggered by decreases in host tree defenses, which are hypothesized to occur with drought stress. Given the persistence of the AMO, the shift to a positive AMO phase in the late 1990s is likely to promote continued spruce beetle disturbance.
本研究考察了 1650 年至 2011 年期间科罗拉多州西北部云杉甲虫（Dendroctonus rufipennis）爆发与气候变率的关系。使用文献记录和树木年轮重建的大规模爆发期可追溯至 1843-1860 年、1882-1889 年、1931-1957 年和 2004-2010 年。爆发期与季节性温度、降水、蒸气压亏缺（VPD）、帕尔默干旱严重指数（PDSI）以及海洋-大气振荡指数进行了比较，这些指数包括厄尔尼诺南方涛动（ENSO）、太平洋十年涛动（PDO）和大西洋多年代际振荡（AMO）。分类树表明，根据平均以上的年度 AMO 值和平均以上的夏季 VPD 值（科罗拉多州干旱的指标），可以最成功地预测爆发。值得注意的是，我们发现，与温度单独预测相比，干旱的年际到多年际变化似乎更能预测云杉甲虫的爆发。这一发现可能意味着，云杉甲虫的爆发是由宿主树木防御能力下降引发的，而干旱应激被假设会导致防御能力下降。鉴于 AMO 的持续存在，20 世纪 90 年代末向正 AMO 阶段的转变很可能会促进云杉甲虫的持续干扰。
