Abstract

Stream restoration includes a number of different approaches intended to reduce sediment and nutrient export. Legacy sediment removal (LSR) and floodplain reconnection (FR) involve removing anthropogenically derived sediment accumulated in valley bottoms to reconnect incised streams to their floodplains. These projects also present an opportunity to create high-quality riparian and wetland plant communities and provide information about the early stages of wetland vegetation development and succession. We surveyed vegetation immediately after restoration at three sites and at three additional sites 1–3 years post-restoration to determine how LSR/FR affects riparian plant communities. Restoration increased the prevalence of hydrophytic herbaceous species at all sites, suggesting these projects successfully reconnected the stream to the floodplain. Pronounced decreases in woody basal area and stem density likely also influenced an increase in native and graminoid species after restoration. Only 16% of the indicator species identified for restored reaches were planted as part of the restoration, suggesting the local seed bank and other seed sources may be important for vegetation recovery and preservation of regional beta diversity. Although vegetation quality increased after restoration in reaches with initially low-quality herbaceous vegetation, vegetation quality did not improve or decreased after restoration in reaches with higher-quality vegetation before restoration. The practice of LSR/FR has the potential to improve the quality of some riparian vegetation communities, but the preservation of high-quality forested areas, even if they are atop legacy sediment terraces, should be considered, particularly if reductions in nutrient export do not offset losses in tree canopy.

中文翻译：

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遗留沉积物清除和洪泛区重新连接对河岸植物群落的影响

摘要

河流恢复包括许多旨在减少沉积物和养分输出的不同方法。遗留沉积物清除（LSR）和洪泛区重新连接（FR）涉及清除谷底积累的人为沉积物，以将下切溪流与其洪泛区重新连接。这些项目还提供了创建高质量河岸和湿地植物群落的机会，并提供有关湿地植被发展和演替早期阶段的信息。我们在恢复后立即对三个地点和恢复后 1-3 年的另外三个地点的植被进行了调查，以确定 LSR/FR 如何影响河岸植物群落。恢复增加了所有地点水生草本物种的流行，表明这些项目成功地将河流与洪泛区重新连接起来。木质断面积和茎密度的显着下降可能也影响了恢复后本地和禾本科物种的增加。在恢复河段确定的指示物种中，只有 16% 作为恢复的一部分进行了种植，这表明当地种子库和其他种子来源可能对于植被恢复和区域 β 多样性的保护很重要。虽然草本植被质量较低的河段恢复后植被质量有所提高，但恢复前植被质量较高的河段恢复后植被质量没有改善或下降。LSR/FR 的实践有可能提高一些河岸植被群落的质量，但应考虑保护高质量的森林地区，即使它们位于遗留沉积物梯田之上，特别是如果养分输出的减少不受影响的话。抵消树冠的损失。