RAPID: Collaborative Research: The 2016 Yellowstone Fires: early indicators of ecosystem transitions in a changing fire regime.

美国西部的森林正面临着比历史上任何时候都更高的气温和更大、更严重的野火。黄石国家公园（怀俄明州）的小杆松林非常适应大的，严重的野火，在过去的10,000年中，每隔100到300年燃烧一次。然而，火灾之间的间隔正在缩短，使得年轻的森林可能会在从以前的火灾中完全恢复之前重新燃烧。森林将如何应对更频繁的火灾和更温暖，更干燥的条件尚不清楚。2016年夏季的野火烧毁了1988年黄石大火后生长的年轻森林（不到30年）。这些最近的火灾产生了一个意想不到的机会，研究短间隔火灾的特点及其对西部松林的影响。在严重火灾后不久取样是必要的，因为火灾后找到烧伤严重程度的现场证据的时间很短，大多数树苗在火灾后的第一年建立。该奖项将衡量2016年燃烧的幼林的燃烧严重程度，树木建立和碳储存。调查结果将立即对区域森林管理人员有用，小型纪录片视频将向广大观众解释火灾活动增加对西部森林的影响。野外数据还将用于改进森林生长的计算机模型，并评估美国北方落基山脉的燃烧严重程度模式。在1988年大火中燃烧的地区进行的野外研究将测试三种假设。(1)短间隔的火灾将降低森林的复原力，因为烧伤将是高度严重的，火灾后针叶树的再生和碳储存将大大减少。(2)火灾后的气候将扩大短火返回间隔的后果，使火灾后针叶树建立将大大减少（或失败）在重新燃烧的条件是温暖和干燥。(3)在区域上，高烈度火灾在短间隔期内的比例将大于长间隔期火灾，但高烈度火灾的景观格局将是相似的。2017年夏季，将按照标准协议在0.25公顷的地块上测量烧伤严重程度、树木再生和碳储存。将进行种子添加实验，以区分种子供应与火灾后气候条件对树苗建立的影响。基于绘图的烧伤严重性数据将用于验证基于卫星的烧伤严重性指标，并绘制跨越北方落基山脉的短间隔火灾中烧伤严重性的空间模式。这项研究将帮助科学家和管理人员了解在未来更多的火灾中可能从根本上改变森林生态系统的条件。

Forests in the western US are facing warmer temperatures and larger, more severe wildfires than at any time in recorded history. Lodgepole pine forests of Yellowstone National Park (Wyoming) are well adapted to large, severe wildfires, which have burned at 100 to 300-yr intervals during the past 10,000 years. However, the interval between fires is shortening, making it likely that young forests will re-burn before fully recovering from previous fires. How forests will respond to more frequent fire and warmer, drier conditions is not known. Wildfires during summer 2016 burned young forests (less than 30 years old) that grew after the momentous 1988 Yellowstone Fires. These recent fires produced an unexpected opportunity to study the characteristics of short-interval fires and their effects on western pine forests. Sampling soon after severe fire is necessary because the time to find field evidence of burn severity is very short after the fire, and most tree seedlings establish during the first year after the fire. This RAPID award will measure burn severity, tree establishment and carbon storage in young forests that burned in 2016. Results will be immediately useful to regional forest managers, and mini-documentary videos will explain effects of increasing fire activity on western forests to a wide audience. Field data also will be used to improve computer models of forest growth and to assess burn-severity patterns across the US northern Rocky Mountains.Field studies in areas burned in the 1988 fires that burned again in 2106 will test three hypotheses. (1) Short-interval fires will reduce forest resilience because burns will be of high severity, and post-fire conifer regeneration and carbon storage will be substantially reduced. (2) Post-fire climate will amplify consequences of short fire-return intervals such that post-fire conifer establishment will be substantially reduced (or fail) in re-burns where conditions are warm and dry. (3) Regionally, the proportion of high-severity fire will be greater in short-interval than long-interval fires, but landscape patterns of high-severity fire will be similar. Burn severity, tree regeneration and carbon storage will be measured during summer 2017 in 0.25-ha plots following standard protocols. A seed addition experiment will be conducted to separate effects of seed supply from post-fire climate conditions on tree seedling establishment. Plot-based burn-severity data will be used to validate satellite-based burn-severity metrics and to map spatial patterns of burn severity in short-interval fires across the Northern Rockies. This study will help scientists and managers understand conditions likely to change forest ecosystems fundamentally in a future with more fire.