1. Although extreme hydrological events are a natural component of river ecosystem disturbance regimes, their frequency is predicted to increase with climate change. Anthropogenic activities have the potential to exacerbate the impact of such disturbances but there are few studies on the combined effects of both anthropogenic and extreme hydrological disturbances on stream ecosystems.
2. We investigated the recovery of stream ecosystems over a 5‐year period following the impact of an anthropogenic (forest clear‐cut harvesting) and an extreme rainfall disturbance (estimated one‐in‐100 year average return interval) that generated debris flows in three headwater streams in New Zealand.
3. Initially, most of the riparian vegetation was eliminated and showed little recovery 1 year later. Subsequent riparian recovery was led by wind‐borne, light‐demanding, pioneering exotic weed species, lengthening and altering the long‐term successional and recovery trajectories to a pre‐disturbance composition of indigenous shrubs.
4. Stream shade, water temperature, and habitat had largely recovered after 5 years. However, the contribution of large wood to channel morphology and in‐stream habitat was compromised due to diminished wood supplies in the stream channel and a hiatus in up‐slope wood inputs until the riparian vegetation re‐establishes and the next crop of trees matures.
5. After an initial decline, most indigenous fish taxa thrived in the post‐disturbance conditions, with significant increases in densities and biomass. The more sensitive fish taxa were scarce or absent, particularly those taxa that prefer pools with overhead and in‐stream cover provided by riparian vegetation and wood. Recovery of these taxa was outside the time frame of this study. Riffle dwelling fish communities were more resilient than pool dwelling fish communities.
6. Invertebrate densities showed a similar response to fish. Post‐event invertebrate community composition differed from that typically found in post‐harvest headwater streams, comprising comparatively lower proportions of Chironomidae, Oligochaetes, and Mollusca taxa, and higher proportions of Trichoptera taxa. Progression toward pre‐event community composition was evident 5 years after the event.
7. The compounding effect of forest removal from harvesting, along with riparian vegetation and wood removal by debris flows, lengthened the recovery of riparian vegetation and wood supplies with cascading effects on in‐stream habitat and biological communities.

中文翻译：

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人为（森林砍伐）和自然（极端降雨事件）干扰对新西兰源头水流的综合影响

1. 尽管极端水文事件是河流生态系统扰动制度的自然组成部分，但预计其发生频率会随着气候变化而增加。人为活动有可能加剧这种干扰的影响，但是关于人为和极端水文干扰对河流生态系统的综合影响的研究很少。
2. 在人类活动（森林砍伐森林）和极端降雨干扰（估计为每100年平均回报间隔）（在三个源头产生泥石流）的影响之后，我们调查了5年内河流生态系统的恢复在新西兰流。
3. 最初，大部分河岸植被被消除，一年后恢复缓慢。随后的河岸恢复是由风传播，轻度需求，开拓性的外来杂草物种带动的，将长期演替和恢复的轨迹延长和改变为原生灌木的干扰前成分。
4. 5年后，溪流阴影，水温和栖息地已基本恢复。但是，由于河道中的木材供应减少以及上坡木材输入的中断，直到河岸植被重新建立且下一批树木成熟之前，大木材对河道形态和河内栖息地的贡献受到了损害。
5. 在最初的下降之后，大多数土著鱼类分类在干扰后的条件下蓬勃发展，密度和生物量显着增加。较不敏感的鱼类类群稀缺或缺乏，特别是那些偏爱河岸植被和木材提供高架和下游覆盖的水池的鱼类。这些分类单元的恢复不在本研究的范围之内。与池栖鱼类群落相比，Riffle鱼类栖居社区更具弹性。
6. 无脊椎动物密度显示出对鱼类的类似反应。事后无脊椎动物群落组成与通常在收获后源头溪流中发现的不同，包括比例较低的Chi科，Ol纲和软体动物类群，以及较高的T翅类生物群。事件发生五年后，活动发生前社区组成的进展明显。
7. 森林采伐，河岸植被和泥石流砍伐木材的复合作用延长了河岸植被和木材供应的恢复时间，对河流生境和生物群落具有连锁效应。