Collaborative Research: The Occurrence of Severe Pacific Northwest Windstorms: A Multi-Century Dendroclimatic Assessment of Their Ecological Impacts

与美国东南部飓风多发地区相比，太平洋西北部的强中纬度气旋受到的关注要少得多，但会产生类似级别和频率的强风事件(HWE)。据记录，这些HWE的风速高达每小时近180英里，可以说是塑造喀斯喀特山脉峰顶以西森林的最重要的干扰物，这意味着它们对森林更新、森林演替和火灾制度产生了区域范围的影响。例如，自1880年以来，至少有五个HWE造成了超过10亿英尺的森林吹倒。最近，2006年和2007年的HWE导致俄勒冈州西部和华盛顿州数百万居民停电。然而，尽管它们具有生态、社会和经济意义，但人们对太平洋西北部HWE的时间、范围、原因和后果知之甚少。这项研究将这些HWE置于更广泛的历史背景下，利用每年树木年轮中的信息，将风事件与已知的十年至百年尺度的气候变化进行比较，并将其发生与森林动态和区域火灾周期联系起来。这些目标将通过基于在太平洋西北部10个地点收集的树木年轮数据的多世纪气候重建以及采用一种研究方案来实现，该研究方案测量并比较被风折断的老树与附近未受破坏的年轻树之间的树木生长后的反应。然后，在被记录的HWE破坏的树木中发现与之匹配的生长异常，以确定在历史记录之前的一段时间内的生长异常：1)使用树生态学技术建立HWE的300年记录；2)量化HWE的频率、严重性、空间分布和天气原因；3)检查HWE与全球和天气尺度气候现象的关系、小冰期的结束以及人类对气候的影响；以及4)估计HWE与降温和降火后的火灾循环有关的生态后果。对HWE的多个世纪的重建和分析将在一个重要但鲜为人知的主题上提供几个公共和科学上的好处。最重要的是为以下方面建立科学基础：1)在启动历史和仪器记录之前估计这些风事件的概率和严重程度；2)评估其生态和潜在的经济影响；以及3)协助机构做好准备。这些发现将有助于未来寻求整合气候学和森林生态学的研究，因为它提供了一种适用于美国东北部等受HWE影响的其他温带地区的方法论方法。这些结果还将促进对风暴如何影响火灾制度的理解，并有助于在气候不确定的时代制定未来的森林管理做法。最后，这项研究将展示HWE如何在十年至世纪的尺度上受到气候变化的影响，并确定HWE与人类引起的气候变化之间的可能联系。

Strong midlatitude cyclones in the Pacific Northwest receive far less attention than the hurricane-prone regions of the southeastern U.S., yet generate high wind events (HWEs) of similar magnitude and frequency. These HWEs, with documented wind speeds up to almost 180 mph, are arguably the most important disturbance agent shaping forests west of the Cascade Range crest, which means that they exert a regional-scale influence on forest regeneration, forest succession, and fire regimes. For example, since 1880 at least five HWEs have each caused forest blowdowns exceeding one billion board feet. More recently, HWEs in 2006 and 2007 caused electrical power outages for millions of residents in western Oregon and Washington. However, despite their ecological, social, and economic significance, little is known about the timing, extent, cause, and consequences of Pacific Northwest HWEs. This research places those HWEs within a broader historical context by using the information in annual tree rings to compare wind events with known decadal-to-century-scale climate variations and to link their occurrence to forest dynamics and regional fire cycles. These objectives will be met using a multi-century climatic reconstruction based on tree-ring data collected at 10 sites in the Pacific Northwest and by employing a research protocol that measures and compares post-HWE tree-growth responses between wind-snapped, old-growth trees to those of younger, nearby undamaged trees. Growth anomalies matching those found in trees damaged by documented HWEs can then be identified for the period before the historical record to: 1) establish a 300-year record of HWEs using dendroecological techniques; 2) quantify the frequency, severity, spatial distribution, and synoptic causes of HWEs; 3) examine the relationship between HWEs and global and synoptic-scale climate phenomena, the end of the Little Ice Age, and anthropogenic influences on climate; and, 4) estimate the ecological ramifications of HWEs related to blowdown and post-blowdown fire cycles. A multi-century reconstruction and analysis of HWEs will provide several public and scientific benefits regarding an important but poorly understood topic. Foremost will be the establishment of a scientific basis for: 1) estimating the probability and severity of these wind events before the initiation of historical and instrumental records; 2) assessing their ecologic and potential economic impacts; and, 3) aiding agency preparedness. These findings will benefit future studies seeking to integrate climatology and forest ecology by providing a methodological approach applicable to other temperate regions affected by HWEs such as the northeastern United States. These results also will promote the understanding of how windstorms influence fire regimes and aid in the development of future forest management practices in an era of climatic uncertainty. Finally, the research will demonstrate how HWEs are influenced by climatic variability at the decadal-to-century scale and identify possible links between HWEs and human-induced climate change.