National Stream and Aquatic Ecology Center, Forest Service, 860 North 1200 East, Logan, Utah, 84321, USA.
PacFish InFish Biological Opinion Effectiveness Program, Forest Service, 860 North 1200 East, Logan, Utah, 84321, USA.
Environ Monit Assess. 2019 Aug 17;191(9):574. doi: 10.1007/s10661-019-7716-5.
Historic management actions authorized or allowed by federal land management agencies have had a profound negative effect on salmon, trout, and char populations and their habitats. To rectify past failings, in the 1990s, federal agencies in the Interior Columbia River Basin modified how they conducted land management activities to foster the conservation of aquatic species. The primary policy changes were to provide additional protection and restoration of lands near streams, lakes, and wetlands. What remains uncertain was whether these changes have altered the trajectory of stream habitat conditions. To address this question, we evaluate the status and trends of ten stream habitat attributes; wood frequency, wood volume, residual pool depth, percent pool, pool frequency, pool tail fines (< 6 mm), median particle size, percent undercut banks, bank angle, and streambank stability in managed and reference catchments following changes in management policies. Our review of these data support the hypothesis that changes made in management standards and guidelines in the 1990s are related to improved stream conditions. Determining the precise magnitude of changes in stream conditions that resulted from the modification of land management policies is difficult due to the shifting environmental baseline. By understanding and accounting for how changes in stream conditions reflect improved land management policies and broader environmental trends, federal agencies will be better situated to make project level decisions that benefit aquatic resources.
历史上，联邦土地管理机构授权或允许的管理行动对鲑鱼、鳟鱼和红点鲑种群及其栖息地产生了深远的负面影响。为了纠正过去的失误，20 世纪 90 年代，哥伦比亚河流域内陆的联邦机构修改了土地管理活动的方式，以促进水生物种的保护。主要的政策变化是为溪流、湖泊和湿地附近的土地提供更多的保护和恢复。仍然不确定的是，这些变化是否改变了溪流生境条件的轨迹。为了解决这个问题，我们评估了十个溪流生境属性的状况和趋势；木材频率、木材体积、残留水池深度、水池百分比、水池频率、水池尾部细粒(<6 毫米)、中值粒径、被切边银行的百分比、河岸角度和河岸稳定性在管理和参考流域中，在管理政策发生变化后。我们对这些数据的审查支持这样一种假设，即在 20 世纪 90 年代，管理标准和准则的变化与溪流条件的改善有关。由于环境基线的变化，确定土地管理政策修改导致的溪流条件变化的确切幅度是困难的。通过了解和考虑溪流条件的变化如何反映出改进的土地管理政策和更广泛的环境趋势，联邦机构将更好地做出有利于水生资源的项目层面决策。
