RAPID: Does riparian vegetation state mediate consequences of climate change-induced extreme flooding for stream-riparian food webs and communities?

2022年6月，北黄石国家公园经历了雨雪事件，导致了500年一遇的洪水，摧毁了当地基础设施，并作为人类造成的气候变化的高调后果引起了公众的关注。极端干扰，无论是5级飓风、严重野火还是极端干旱，都变得更加频繁和强烈。自然资源管理者和政策制定者需要了解这种极端干扰的后果，并找到支持生态系统弹性的方法。从历史上看，生态学家认为，尽管生态系统对轻度或中度干扰具有弹性，甚至受益于轻微或中度干扰，但极端干扰会将生态系统“重置”到某种统一的基线状态。NSF已经批准了对该项目的快速支持，以评估北黄石地区的极端干扰。研究区域在不同的生境镶嵌中包含了相当多的生物多样性。这种复杂性的一个来源是狼和灰熊等捕食者的恢复，它们与麋鹿和野牛等食草动物的互动，以及随后植物群落的变化。结果，柳树和杉木在一些小溪和河流周围重新生长，而其他一些小溪和河流只有几英里远，仍然以草和莎草为主。以往的研究表明，不同的植物群落影响小溪和河流的多样性和生产力，但影响方式受当地环境的影响，导致生态系统状态的马赛克。就像捕食者的恢复并没有统一地改变这个生态系统一样，对最近的极端洪水的反应可能受到当地背景的影响。反过来，这项研究的结果可能会为管理决策提供信息，并影响公众对这类干扰后果的看法，就像过去的生态学研究对该地区的野火所做的那样。通过机会主义地使用自然实验，并通过比较极端洪水前后的溪流-河岸生态系统，该项目将评估是否发生了溪流-河岸生态系统的同质“重置”，或者是否影响河岸植被状态的陆地野生动物动态以及水生群落的洪水前特征，调节了溪流-河岸生物和生态系统过程的异质反应。该项目将收集洪灾后与之前收集的平行测量数据，包括溪流-河岸栖息地特征、草食和河岸植物群落组成和结构、河流生态系统有机质动态、水生无脊椎动物和鱼类以及河岸蜘蛛和鸟类群落的生产力和食物网相互作用。如果生物体、群落或食物网的特征塑造了极端洪水后的抵抗力、恢复力和变化轨迹，这将提供一个机会来评估这种“生态记忆”如何限制对未来极端事件的反应。如果生物体和群落的特征对于调解极端干扰的反应确实很重要，该项目可能会突出在气候变化和生物多样性危机面前保护这种复杂性的重要性。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

In June 2022, Northern Yellowstone National Park experienced rain-on-snow events leading to a 1 in 500-year flood, devastating local infrastructure and capturing public attention as a high-profile consequence of human-caused climate change. Extreme disturbances, whether they be category 5 hurricanes, severe wildfires, or extreme droughts, are becoming more frequent and intense. Natural resource managers and policy makers need to understand the consequences of such extreme disturbances and find ways to support ecosystem resiliency. Historically, ecologists thought that though ecosystems were resilient to, or even benefitted from, mild or moderate disturbances, extreme disturbances “reset” ecosystems to some uniform, baseline state. NSF has approved RAPID support for this project, to evaluate extreme disturbance in the context of Northern Yellowstone. The study area contains considerable biodiversity throughout a mosaic of distinct habitats. One source of this complexity comes from the restoration of predators like wolves and grizzly bears, their interactions with herbivores such as elk and bison, and the subsequent changes to plant communities. As a result, willows and alders have regrown around some streams and rivers while others, just miles away, remain dominated by grasses and sedges. Previous investigations showed that different plant communities influence the diversity and productivity of streams and rivers, but in ways mediated by local context that result in a mosaic of ecosystem states. Just as the restoration of predators has not uniformly changed this ecosystem, responses to the recent extreme flooding may have been mediated by local context. In turn, results from this study may inform management decisions and influence public perceptions regarding consequences of such disturbances, as indeed past ecological studies have done for wildfire in this region.Through the opportunistic use of a natural experiment and by comparing stream-riparian ecosystems before and after the extreme flooding, this project will evaluate whether a homogenous “reset” of stream-riparian ecosystems occurred, or if terrestrial wildlife dynamics that influence riparian vegetation state, as well as pre-flood traits of aquatic communities, mediated heterogeneous responses of stream-riparian organisms and ecosystem processes. This project will collect parallel measurements after flooding to those collected before, including stream-riparian habitat characteristics, herbivory and riparian plant community composition and structure, stream ecosystem organic matter dynamics, productivity and food web interactions of aquatic invertebrates and fish, and riparian spider and bird communities. If organism, community, or food web traits shape resistance, resilience, and trajectories of change following the extreme flood, this will provide an opportunity to evaluate how such “ecological memory” constrains responses to future extreme events. If traits of organisms and communities are indeed important to mediating responses to extreme disturbances, this project may highlight the importance of conserving such complexity in the face of climate change and the biodiversity crisis.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.