Landscape Configurations in Yellowstone National Park: An Alternative State Stabilized by Herbivory?

人类的行为会对自然造成意想不到的影响。通常，这些行为会导致自然系统突然从其历史状态转变为可能不受欢迎的新状态。把狼从黄石国家公园赶走似乎对公园的生态系统造成了意想不到的损害，特别是河流走廊上的树木和灌木的损失。这些植物改善水质，稳定河岸，并为许多野生动物提供栖息地。狼的灭绝似乎使麋鹿的数量达到了一个水平，在这个水平上，它们的觅食阻止了柳树的繁殖，增加了柳树的死亡率。海狸的消失和大部分柳树栖息地的消失，导致溪流发生了根本性的变化，使它们不太适合柳树的栖息地。这项研究将确定在黄石国家公园重新引入狼是否能使北部地区恢复到历史上繁茂的柳树群落和旺盛的海狸种群的状态。将使用几种方法，包括评估航空照片和系统的定量建模。美国国家科学院的一份报告指出，了解水的可用性和麋鹿对柳树群落的影响，对黄石国家公园的政策和管理来说是一个迫切重要的问题。拟议的工作将在一个科学可以立即应用的地方解决一个具有基本科学价值的问题。这项工作为向公民、管理者和决策者传播科学提供了一个宝贵的机会。

Human actions can cause unintended effects on nature. Often, these actions can cause natural systems to change abruptly from their historic condition to new conditions that may be undesirable. The removal of wolves from Yellowstone National Park appears to be an action that has caused unanticipated harm to the ecosystems of the park, in particular, the loss of trees and shrubs from stream corridors. These plants enhance water quality, stabilize stream banks, and provide habitat for many species of wildlife. It appears that elimination of wolves allowed elk populations to reach levels where their browsing prevented willow reproduction and increased willow mortality. The absence of beaver with the demise of much of the willow habitat, resulted in fundamental changes in streams, rendering them less suitable as habitat for willows. This study will determine whether the re-introduction of wolves to Yellowstone National Park has allowed the northern range to recover to its historic condition with abundant willow communities and vigorous populations of beaver. Several approaches will be used including assessments of aerial photographs and quantitative modeling of the system.A National Academy of Sciences report identified understanding the effects of availability of water and browsing by elk on communities of willows as a problem of urgent importance for policy and management in Yellowstone National Park. The proposed work will address a problem of fundamental scientific value in a location where science can be immediately applied. The work provides a valuable opportunity to communicate science to citizens, managers and policy makers.