U.S. Geological Survey, Northern Rocky Mountain Science Center, 2327 University Way, Suite 2, Bozeman, Montana, 59715, USA.
School of Environmental and Forest Sciences, University of Washington, Seattle, Washington, 98195, USA.
Ecology. 2019 Apr;100(4):e02638. doi: 10.1002/ecy.2638. Epub 2019 Mar 13.
Although increased frequency of extreme-weather events is one of the most secure predictions associated with contemporary climate change, effects of such events on distribution and abundance of climate-sensitive species remain poorly understood. Montane ecosystems may be especially sensitive to extreme weather because of complex abiotic and biotic interactions that propagate from climate-driven reductions in snowpack. Snowpack not only protects subnivean biotas from extreme cold, but also influences forage availability through timing of melt-off and water availability. We related relative abundances of an alpine mammal, the American pika (Ochotona princeps), to measures of weather and snowpack dynamics over an 8-yr period that included before and after a year of record-low snowpack in Washington, USA. We sought to (1) quantify any change in pika abundance associated with the snowpack anomaly and (2) identify aspects of weather and snowpack that influenced abundance of pikas. Pikas showed a 1-yr lag response to the snowpack anomaly and exhibited marked declines in abundance at elevations below 1,400 m simultaneous with increased abundances at higher elevations. Atmospheric moisture, indexed by vapor pressure deficit (VPD), was especially important, evidenced by strong support for the top-ranked model that included the interaction of VPD with snowpack duration. Notably, our novel application of VPD from gridded climate data for analyses of animal abundances shows strong potential for improving species distribution models because VPD represents an important aspect of weather that influences the physiology and habitat of biota. Pikas were apparently affected by cold stress without snowpack at mid elevations, whereas changes to forage associated with snowpack and VPD were influential at high and low elevations. Our results reveal context dependency in pika responses to weather and illustrate how snow drought can lead to rapid change in the abundance of subnivean animals.
尽管极端天气事件的频率增加是与当代气候变化相关的最可靠预测之一，但这些事件对气候敏感物种的分布和丰度的影响仍知之甚少。由于复杂的非生物和生物相互作用，从气候驱动的积雪减少中传播，高山生态系统可能对极端天气特别敏感。积雪不仅保护亚雪生物免受极端寒冷的影响，而且还通过融雪时间和水的可用性来影响饲料的可用性。我们将高山哺乳动物美洲旱獭（Ochotona princeps）的相对丰度与美国华盛顿州 8 年期间的天气和积雪动态测量值相关联，其中包括记录到的积雪量异常的一年之前和之后。我们试图（1）量化与积雪异常相关的旱獭丰度的任何变化，（2）确定影响旱獭丰度的天气和积雪方面。旱獭对积雪异常表现出 1 年的滞后反应，并且在海拔 1400 米以下的海拔高度同时表现出明显的丰度下降，而在较高海拔高度的丰度增加。大气湿度，以蒸气压亏缺（VPD）为指标，尤其重要，强有力地支持了包含 VPD 与积雪持续时间相互作用的排名最高的模型。值得注意的是，我们将 VPD 从网格化气候数据应用于动物丰度分析，这表明 VPD 作为影响生物群生理和栖息地的天气的重要方面，具有改进物种分布模型的巨大潜力。在中海拔处没有积雪的情况下，旱獭显然受到冷应激的影响，而与积雪和 VPD 相关的饲料变化在高海拔和低海拔处有影响。我们的研究结果揭示了旱獭对天气的反应的背景依赖性，并说明了雪干旱如何导致亚雪动物数量的快速变化。
