Geomorphic Impacts of Catastrophic Fire in Ponderosa Pine Ecosystems: Modern and Holocene Perspectives from Granitic Mountains of Central Idaho

灾难性火灾对黄松生态系统的地貌影响：爱达荷州中部花岗岩山脉的现代和全新世视角

• 批准号: 0000905
• 负责人: Grant Meyer
• 金额: $ 13.76万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-02-15 至 2000-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0000905&HistoricalAwards=false
• 关键词: Geomorphic; Impacts; Catastrophic; Fire; Ponderosa

0000905MeyerIn recent decades, large canopy fires have swept through ponderosa pine forests of the semi-arid western United States. In central Idaho, ~300-year tree-ring records indicate a dramatic decrease in the frequency of low-intensity surface fires in the early 1900s, suggesting that fire suppression and fuel buildup due are largely responsible for recent catastrophic burns. The role of climatic variations in changing fire regimes, however, is much less understood. Intensified burning and ensuing slope erosion might also be a symptom of climatic warming over the last century, leading to unusually severe droughts and intense convective storms. Thus, are recent canopy fires, slope erosion, and debris flows in ponderosa pine forests truly exceptional in postglacial history? What has been the frequency and magnitude of these events in the past? And, has the frequency of severe fires and slope erosion changed in response to Holocene climatic variations?We will address these questions through the Holocene stratigraphic record in numerous small alluvial fans in the Payette River drainage of central Idaho. Recent debris-flow and flood events from burned basins allow development of facies models for distinguishing fire-related sediments in fan stratigraphic sections. Burned soil surfaces provide unambiguous stratigraphic markers and accurate fire dates, and fire-related debris-flow deposits are datable evidence of both intense canopy fires and geomorphic response. A large set of 14C dates will yield estimates of the probability and frequency of fire-related sedimentation events over time and space. Dating of colluvial slope deposits and mainstem fluvial activity will combine with alluvial fan records to allow comprehensive system-wide analysis of Holocene geomorphic response to fire, climatic change, and intrinsic controls. It will also provide a long-term context for understanding fire regimes in ponderosa pine ecosystems and natural hazards in mountain environments.

0000905Meyer近几十年来，大型林冠火灾席卷了美国西部半干旱地区的黄松森林。 在爱达荷州中部，约300年的树木年轮记录表明，20世纪初低强度地表火灾的频率急剧下降，这表明灭火和燃料积聚是最近灾难性燃烧的主要原因。 然而，人们对气候变化在改变火灾状况中的作用了解得少得多。 加剧的燃烧和随之而来的坡面侵蚀也可能是上个世纪气候变暖的一个症状，导致异常严重的干旱和强烈的对流风暴。 因此，最近的林冠火灾，斜坡侵蚀，并在黄松森林泥石流真正例外在冰后期的历史？ 过去这些事件的频率和严重程度如何？ 而且，严重的火灾和坡面侵蚀的频率是否因全新世气候变化而改变？我们将通过爱达荷州中部帕耶特河流域许多小冲积扇的全新世地层记录来解决这些问题。 最近的泥石流和洪水事件从燃烧盆地允许发展相模式区分火灾相关的沉积物在扇地层剖面。 燃烧过的土壤表面提供了明确的地层标志和准确的火灾日期，与火灾有关的碎屑流沉积物是强烈的林冠火灾和地貌反应的可追溯证据。 一个大的14C日期集将产生随着时间和空间的概率和频率的火灾相关的沉积事件的估计。 崩积斜坡沉积物和主干河流活动的年代测定将结合联合收割机与冲积扇记录，以便对全新世地貌对火灾、气候变化和内在控制的反应进行全面的系统分析。 它还将为理解黄松生态系统的火灾机制和山区环境中的自然灾害提供长期背景。