LTREB Renewal: Understanding controls on state-transition on Yellowstone's northern range

LTREB 更新：了解对黄石北部山脉状态过渡的控制

• 批准号: 1655035
• 负责人: N. Thompson Hobbs
• 金额: $ 44.99万
• 依托单位: Colorado State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-03-01 至 2022-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1655035&HistoricalAwards=false
• 关键词: LTREB; Renewal; Understanding; controls; state

The extirpation and subsequent reintroduction of the gray wolf to Yellowstone National Park has provided a rare opportunity to understand how predators can change ecosystems. Originally it was thought the loss of wolves would lead to a dramatic increase in the number of elk, which in turn would lead to substantial changes in the willows along the park's streams. It was expected that reintroduction of wolves would cause a rapid restoration of willow communities due declines in elk numbers. However, the first fifteen years of research indicates that the fate of the willow communities is complex, involving interactions among wolves, elk, bison, beavers and available water. This research will focus on how these complex interactions among predators, grazing animals, and local hydrology influence plants on landscapes. This knowledge forms the scientific foundation for managing rangelands throughout the western United States, and in so doing, enhances human economies throughout the region. The unfolding story of wolves in Yellowstone is of great public interest and will be communicated in the popular media. The researchers will collaborate with park staff in Yellowstone to offer citizen education to four million visitors annually. Data and conclusions will be made easily available to the public, to natural resource managers, and to researchers throughout the United States. The extirpation of wolves from Yellowstone National Park at the turn of the century allowed elk populations to increase to levels that degraded vegetation along small streams. Historically abundant willows were eliminated and dam building by beaver ceased. The reintroduction of wolves to Yellowstone National Park in 1995 caused a dramatic decline in the number of elk grazing on the park?s northern range, creating an unusual opportunity to understand how herbivores influence plant communities. It has been hypothesized that effects of wolves on elk caused a rapid restoration of riparian communities by reducing browsing on willows. The research team has conducted a 15-year, manipulative experiment to test this hypothesis and to understand the roles of herbivory and water availability in controlling willow growth. The experiment found little support for the idea that wolves changed the ecosystem by releasing plants from consumption by elk. Instead, availability of water controlled willow response. The experiment showed that the absence of effects of effects of reduced elk numbers on willows on the northern range is explained by the absence of dam building by beaver, an activity that enhances availability of water for willows. Beavers, in turn, need willows for food and dam building materials. Patchy recovery of willows has allowed beaver to return recently to a few small streams. Dams built on these streams, in turn, may accelerate the recovery of willows. Alternatively, consumption of willows by increasingly abundant bison populations may compete with beavers and prevent them from maintaining dams, preventing widespread willow recovery. Researchers will continue their experiment on willow growth, supplementing it with observations on effects of natural beaver dams on willows to understand how effects of wolves, elk, bison, and beavers act to determine the state of the riparian ecosystem. State-of-the-art statistical models will be used to analyze data. Results will have important implications for understanding and managing riparian zones embedded within semi-arid grassland landscapes worldwide.

灰狼的灭绝和随后的重新引入黄石国家公园提供了一个难得的机会来了解捕食者如何改变生态系统。最初，人们认为狼的消失会导致麋鹿数量的急剧增加，这反过来又会导致公园沿着的柳树发生重大变化。由于麋鹿数量的下降，预计狼的重新引入将导致杨柳社区的迅速恢复。然而，前十五年的研究表明，杨柳群落的命运是复杂的，涉及狼、麋鹿、野牛、海狸和可用水之间的相互作用。这项研究将集中在捕食者，放牧动物和当地水文之间的这些复杂的相互作用如何影响植物景观。 这些知识构成了管理整个美国西部牧场的科学基础，从而加强了整个地区的人类经济。黄石公园狼的故事引起了公众的极大兴趣，并将在大众媒体上传播。研究人员将与黄石公园的工作人员合作，每年为400万游客提供公民教育。数据和结论将很容易地提供给公众，自然资源管理人员和美国各地的研究人员。 在世纪之交，黄石国家公园的狼被灭绝，麋鹿的数量增加到了使沿着小溪的植被退化的程度。历史上大量的柳树被淘汰，河狸建造的水坝也停止了。1995年黄石国家公园重新引入狼导致公园里吃草的麋鹿数量急剧下降？的北方范围，创造了一个不寻常的机会，了解如何食草动物影响植物群落。据推测，狼对麋鹿的影响导致了河岸群落的快速恢复，减少了对柳树的浏览。研究小组进行了一项为期15年的操纵实验来验证这一假设，并了解食草动物和水的可用性在控制杨柳生长中的作用。实验发现，狼通过释放麋鹿食用的植物来改变生态系统的想法几乎没有得到支持。相反，水的可用性控制杨柳的反应。实验表明，麋鹿数量减少对北方山脉柳树的影响的缺乏是由海狸没有筑坝来解释的，海狸筑坝是一种提高柳树供水量的活动。河狸则需要柳树作为食物和水坝建筑材料。柳树的零星恢复让海狸最近回到了几条小溪。反过来，在这些溪流上建造水坝可能会加速柳树的恢复。另外，日益丰富的野牛种群对柳树的消费可能会与海狸竞争，并阻止它们维护水坝，从而阻止广泛的杨柳恢复。研究人员将继续他们对杨柳生长的实验，并观察天然海狸坝对柳树的影响，以了解狼、麋鹿、野牛和海狸的影响如何决定河岸生态系统的状态。将使用最先进的统计模型分析数据。结果将有重要的影响，了解和管理河岸带嵌入在世界各地的半干旱草原景观。