Large wood (LW) additions are commonly used to restore degraded streams, particularly in regenerating forests that have low LW recruitment due to past logging. While the short-term effects of LW input on stream structure and function are well studied, the long-term dynamics of added wood are less documented. We assessed the long-term movement and condition of LW added to three small (mean discharge, 28–47 L s⁻¹) midwestern USA streams. In 2004, 25 aspen logs (2.5 m L × 0.5 m D) were added to 100-m treatment reaches of three replicate streams in northern Michigan, USA, that contained low prior LW abundance. We monitored log movement and evaluated factors contributing to that movement over 14 years. Across all three streams, 41 of the 75 added logs moved downstream, with a mean travel distance of 4.0 m (SD, 7.0 m; n = 75). However, all logs still remained within their original reaches. Most log movements occurred within the first 3 years following placement and were associated with high flow events. Individual log mobility was related to position in the channel; logs that were at least 70% submerged, and near horizontal in inclination, accounted for 83% of the single movements ≥0.5 m. In addition, after 14 years 32% of logs became part of aggregations and 86% displayed substantial decay. Our study suggests that restoration efforts that add LW to small, groundwater-dominated streams can pose minimal risk to downstream reaches or human structures and may provide sustained ecological benefits to the ecosystem.

中文翻译：

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美国中西部河流中添加的大木头动态

添加大量木材 (LW) 通常用于恢复退化的河流，特别是在由于过去的伐木而导致 LW 补充量较低的再生森林中。虽然 LW 输入对河流结构和功能的短期影响得到了很好的研究，但添加木材的长期动态记录较少。我们评估了 LW 添加到三个小（平均流量，28-47 L s ^-1) 美国中西部的溪流。2004 年，在美国密歇根州北部三个重复流的 100 米处理河段中添加了 25 根白杨原木（2.5 m L × 0.5 m D），这些流域之前的 LW 丰度较低。我们监测了原木移动并评估了 14 年来促成该移动的因素。在所有三个溪流中，添加的 75 个原木中有 41 个向下游移动，平均移动距离为 4.0 m（SD，7.0 m；n = 75）。然而，所有的原木仍然保留在它们原来的范围内。大多数原木移动发生在放置后的前 3 年内，并且与高流量事件相关。单个日志移动性与通道中的位置有关；至少 70% 淹没在水中且倾斜度接近水平的原木占 83% ≥0.5 m 的单次运动。此外，14 年后，32% 的原木成为聚合体的一部分，86% 显示出实质性衰减。我们的研究表明，将 LW 添加到以地下水为主的小型溪流中的恢复工作可以对下游河段或人类结构造成最小的风险，并可能为生态系统提供持续的生态效益。