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

太平洋西北地区的强中纬度气旋受到的关注远远低于美国东南部飓风多发地区，但却产生了类似强度和频率的强风事件 (HWE)。 这些 HWE 的记录风速高达近 180 英里/小时，可以说是塑造喀斯喀特山脉顶部以西森林的最重要的干扰因素，这意味着它们对森林再生、森林演替和火灾状况产生区域性影响。 例如，自 1880 年以来，至少有 5 起 HWE 造成的森林排污量均超过 10 亿板英尺。 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，尽管其生态、社会和经济意义重大，但人们对太平洋西北地区 HWE 的时间、范围、原因和后果知之甚少。这项研究通过使用年轮中的信息将这些 HWE 置于更广泛的历史背景中，将风事件与已知的十年到世纪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循环联系起来。这些目标将通过基于在太平洋西北地区 10 个地点收集的树木年轮数据进行的多世纪气候重建来实现，并采用一项研究协议来测量和比较被风吹断的老树与附近未受损的年轻树木之间的 HWE 后树木生长反应。然后，可以识别历史记录之前的一段时间内与被记录的 HWE 损坏的树木中发现的生长异常相匹配的生长异常，以便：1）使用树木生态学技术建立 300 年的 HWE 记录； 2) 量化 HWE 的频率、严重程度、空间分布和天气原因； 3）研究HWE与全球和天气尺度气候现象、小冰河时代的结束以及人为对气候的影响之间的关系； 4) 估计与排污和排污后火灾循环相关的 HWE 的生态影响。对 HWE 进行多个世纪的重建和分析将为一个重要但知之甚少的主题提供一些公共和科学效益。最重要的是建立科学基础：1）在开始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）评估其生态和潜在经济影响； 3) 协助机构做好准备。 这些发现将有利于未来寻求整合气候学和森林生态学的研究，提供适用于美国东北部等受 HWE 影响的其他温带地区的方法。 这些结果还将促进对风暴如何影响火灾状况的理解，并有助于在气候不确定的时代发展未来的森林管理实践。 最后，该研究将展示十年至世纪尺度的气候变化如何影响 HWE，并确定 HWE 与人类引起的气候变化之间可能的联系。

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.