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、更大、更严重的野火。黄石国家公园（怀俄明州）的Lodgepole松林很好地适应了大型、严重的野火，在过去的一万年里，每隔100到300年就会发生一次野火。然而，火灾之间的间隔正在缩短，这使得年轻的森林在完全从以前的火灾中恢复之前可能会重新燃烧。森林将如何应对更频繁的火灾和更温暖、更干燥的环境尚不清楚。2016年夏天的野火烧毁了1988年黄石大火后生长的年轻森林（不到30岁）。这些最近的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。在严重火灾发生后立即取样是必要的，因为在火灾发生后寻找烧伤严重程度的现场证据的时间很短，而且大多数树苗在火灾发生后的第一年就长好了。该RAPID奖将衡量2016年燃烧的年轻森林的燃烧严重程度、树木建立和碳储量。研究结果将立即对区域森林管理人员有用，小型记录片将向广大观众解释日益增加的火灾活动对西部森林的影响。野外数据还将用于改进森林生长的计算机模型，并评估美国北部落基山脉的烧伤严重程度。对1988年大火烧毁的地区进行实地研究，并在2106年再次燃烧，将检验三个假设。(1)短间隔火灾会降低森林的恢复力，因为火灾严重程度高，火灾后针叶林的更新和碳储量会大大减少。(2)火灾后的气候将放大短回火间隔的后果，这样，在温暖干燥的条件下，火灾后针叶树的生长将大大减少（或失败）。(3)从区域上看，短间隔高烈度火灾的比例大于长间隔火灾，但高烈度火灾的景观格局相似。烧伤严重程度、树木再生和碳储量将在2017年夏季按照标准方案在0.25公顷的地块上进行测量。将进行种子添加试验，以分离种子供应与火灾后气候条件对树苗形成的影响。基于图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指标，并绘制北落基山脉短间隔火灾中烧伤严重程度的空间格局。这项研究将帮助科学家和管理者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.