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温暖的温度和更大、更严重的野火。黄石国家公园(怀俄明州)的小松林很好地适应了大火，在过去的10,000年里，这种大火每隔100到300年就会燃烧一次。然而，火灾之间的间隔正在缩短，这使得幼林很可能会在从之前的火灾中完全恢复之前再次燃烧。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年夏天的野火烧毁了1988年黄石公园大火后生长的幼林(不到30年的树龄)。最近的这些火灾为研究短间隔火灾的特征及其对西部松林的影响提供了一个意想不到的机会。在严重火灾后立即取样是必要的，因为在火灾后找到烧伤严重程度的现场证据的时间非常短，而且大多数树苗都是在火灾后的第一年建立起来的。这一快速奖项将衡量2016年被烧毁的幼林的烧伤严重程度、树木建立和碳储量。结果将立即对区域森林管理者有用，迷你纪录片将向广大观众解释西部森林火灾活动增加的影响。现场数据还将用于改进森林生长的计算机模型，并评估美国北部落基山脉的烧伤严重程度模式。在1988年再次发生火灾的地区进行的实地研究将检验三个假设。(1)短时间的火灾将降低森林的复原力，因为燃烧将是高度严重的，火灾后针叶树的再生和碳储存将大幅减少。(2)火后气候将放大短火返间隔的后果，使得在条件温暖和干燥的再燃烧中，火后针叶树的建立将大大减少(或失败)。(3)从区域上看，短间隔内高烈度火的比例大于长间隔火，但高烈度火的景观格局相似。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。将进行种子添加试验，以区分种子供应和火灾后气候条件对林木成苗的影响。基于情节的烧伤严重程度数据将用于验证基于卫星的烧伤严重程度衡量标准，并绘制北落基山脉短时间间隔火灾中烧伤严重程度的空间模式。这项研究将帮助科学家和管理人员了解未来更多火灾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.