Collaborative: How the Timing of Summer Precipitation Affects the Responses of Boreal Forest to Climate Change

合作：夏季降水时间如何影响北方森林对气候变化的响应

• 批准号: 0902169
• 负责人: Daniel Mann
• 金额: $ 79.71万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-07-01 至 2013-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0902169&HistoricalAwards=false
• 关键词: Collaborative; How; Timing; Summer; Precipitation

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).AbstractThere is increasing evidence that ecological processes at high latitude are just as sensitive to the timing of events as to their magnitudes. In the boreal forest, moisture availability in summer affects both tree growth and the fire regime. Summers are brief and seasonal transitions rapid, so even slight shifts in the timing of precipitation patterns can have large impacts. One of the most striking, seasonal phenomena in the Alaskan boreal forest is the onset of frequent frontal storms in late summer. This event usually comes in mid-July but is delayed into August or even September in some years. Summers when the rains are delayed have a greater chance of being mega-fires seasons when 1.6 million ha burn. This project will test the hypothesis that shifts in the seasonality of warm-season precipitation could be a key driver of the boreal forest?s responses to future climate changes. The effect of late-summer precipitation on tree growth and fire in Alaska will be quantified in two ways: First, by analyzing interactions between climate, fire, and tree growth (specifically ring-width, ring density, and wood-isotope composition); second, by analyzing fire-climate relationships using a new statistical approach. Together, these results will improve parameterization of the forest model ALFRESCO, which will then be used to test additional hypotheses about the interconnections among future climates, tree growth, fire, and their collective feedbacks to the global climate system. The shifting seasonality of water availability during the warm season may be of key importance in determining how the global boreal forest responds to future climate changes. The multidisciplinary research proposed here represents a new approach to answering a novel question. No one has examined the impacts of seasonal shifts in the timing and magnitude of warm-season precipitation on vegetation distribution, tree growth, and fire regime in the boreal forest before. This will be the first time that tree rings from deciduous species in the boreal forest are used to describe past variations in summer rainfall through measurements of ring-width, late-wood density, and wood isotopes. The generalized boosting technique we propose using has not been previously applied to climate-fire records. The results of these tree-ring and statistical analyses will improve parameterization of the ALFRESCO forest model and allow us to explore the interactions among components of this part of the Arctic system with greater realism.

该奖项是根据2009年的《美国复苏与再投资法》（公法111-5）资助的。在北方森林中，夏季的水分可用性会影响树木的生长和火灾状况。夏天是短暂的，季节性的过渡迅速，因此，降水模式时机的略有变化也会产生巨大的影响。阿拉斯加北方森林中最引人注目的季节性现象之一是夏末经常发生的额叶风暴。这项活动通常是在7月中旬进行的，但在几年内被推迟到八月甚至9月。夏天，当降雨时，当160万公顷燃烧时，降雨时有更大的机会成为大型赛季。该项目将检验以下假设：暖季降水的季节性变化可能是北方森林对未来气候变化的反应的主要驱动力。晚夏末降水对阿拉斯加树木生长和火灾的影响将通过两种方式进行量化：首先，通过分析气候，火和树木生长之间的相互作用（特别是环宽，环密度和木材 - 异位素组成）；其次，通过使用新的统计方法分析火灾气候关系。这些结果共同改善了森林模型露天Co的参数化，然后将其用于测试有关未来气候，树木生长，火灾及其对全球气候系统的集体反馈之间相互联系的其他假设。在温暖季节，水利用性的季节性变化对于确定全球北方森林如何应对未来气候变化的关键。这里提出的多学科研究代表了一种回答新问题的新方法。以前，没有人检查过季节性转变的影响和暖季降水的时间和大小对北方森林中植被分布，树木生长和火灾制度的影响。这将是第一次使用北方森林中落叶物种的树环来描述夏季降雨中的过去变化，通过测量环宽度，晚木密度和木材同位素。我们建议使用的广义增强技术先前尚未应用于气候火灾记录。这些树环和统计分析的结果将改善露天林林模型的参数化，并使我们能够以更大的现实主义探索北极系统这一部分组成部分之间的相互作用。