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首页> 外文期刊>Freshwater science >Knickpoint effects on macroinvertebrates, sediment, and discharge in urban and forested streams: urbanization outweighs microscale habitat heterogeneity
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Knickpoint effects on macroinvertebrates, sediment, and discharge in urban and forested streams: urbanization outweighs microscale habitat heterogeneity

机译：拐点对城市和森林河流中大型无脊椎动物，沉积物和排放的影响：城市化胜过微观生境的异质性

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摘要

Knickpoints are dynamic geomorphic formations in the longitudinal stream profile that have long been a subject of interest for geomorphologists, but have been largely unstudied in stream ecology. We measured discharge, bed sediment, and macroinvertebrate communities around knickpoints in forested and urban catchments. Knickpoints introduced microscale heterogeneity in discharge. This heterogeneity may be important in providing refugia for benthic biota during low-flow conditions, depending on the condition of the bed sediment below the knickpoint, which was highly variable. In addition, knickpoints supported a unique filterer-dominated community of macroinvertebrates not found elsewhere in the stream reach. The knickpoint itself also may maintain a higher overall density of macroinvertebrates in comparison to other habitats in the stream reach, but this prediction was only weakly supported. Instead, the largest differences in macroinvertebrate community metrics were consistently between urban and forested knickpoints. Decreases in density, species richness, and diversity from forested to urban knickpoints greatly outweighed any longitudinal differences in the macroinvertebrate community within individual knickpoint sites. Thus, we conclude that knickpoints may serve as hotspots of biodiversity and provide substantial habitat heterogeneity over a small area, but the valleyscale influence of catchment land use far outweighs the effect of these microscale geomorphic features in influencing benthic communities.
机译：拐点是纵向河流剖面中的动态地貌构造，长期以来一直是地貌学家关注的主题，但在河流生态学中却尚未对其进行研究。我们测量了森林和城市集水区拐点附近的流量，河床沉积物和大型无脊椎动物群落。 Knickpoints在放电中引入了微观异质性。这种异质性可能在低流量条件下为底栖生物群提供避难所方面很重要，具体取决于床底沉积物在拐点以下的状况，而后者是高度可变的。此外，拐点支持了一个独特的以过滤器为主的大型无脊椎动物群落，这在河段其他地方都找不到。与河段其他栖息地相比，拐点本身还可以维持更高的整体无脊椎动物密度，但是这一预测仅得到了较弱的支持。取而代之的是，大型无脊椎动物群落指标的最大差异始终是城市和森林的拐点之间。从森林拐点到城市拐点的密度，物种丰富度和多样性的下降大大超过了单个拐点内大型无脊椎动物群落的纵向差异。因此，我们得出的结论是，拐点可能会成为生物多样性的热点，并在小范围内提供大量的栖息地异质性，但是流域土地利用的谷尺度影响远大于这些微观尺度地貌特征对底栖生物的影响。

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