White Julia Y, Walsh Christopher J
School of Ecosystem and Forest Sciences, The University of Melbourne, Burnley, Victoria, Australia.
Ecol Appl. 2020 Dec;30(8):e02199. doi: 10.1002/eap.2199. Epub 2020 Jul 20.
While provision of in-stream habitat complexity remains common practice in efforts to restore streams, the evidence of positive effects on in-stream communities is inconsistent. In streams of urban catchments, where both reach-scale habitat manipulation and catchment-scale actions to ameliorate the disturbance regime of urban stormwater runoff are common management responses, clearer understanding of the effects of habitat complexity under different degrees of urban impact are needed. We experimentally assessed the effect of increased surface complexity in wood, the dominant hard substrate in our 18 study reaches on 14 small streams, on in-stream macroinvertebrate assemblages across a range of urban impact. Increased surface complexity increased abundance of most taxa, but this effect was less pronounced in urban streams, partly because of the reduced species pool tolerant of urban stormwater impacts, and partly because of a lesser response of some species to increased complexity in more urban streams. Collectively these taxon-specific effects resulted in small, uncertain increases in taxon richness with increased complexity in rural streams, and no change in richness of the less diverse assemblages of urban streams. Increased abundances suggest increased availability of refugia or resources with increased surface complexity, while the reduced effect of complexity in urban streams suggests that any refuge or resource provided by greater surface complexity is less effective in more disturbed environments receiving urban stormwater runoff. The reduced abundance of sensitive taxa in more urban streams, and the resultant reduced richness, confirms that urban stormwater runoff acts as a strong environmental filter, limiting the species pool available for community assembly. Restoration of habitat complexity in streams without catchment-scale drivers of degradation is likely to have positive benefits to in-stream biotic assemblages, but the efficacy of such approaches in catchments subject to urban stormwater runoff will be greatly diminished. In such cases, restoration activities should first be aimed at controlling the larger-scale problem.
虽然在溪流恢复工作中，提供河流水生栖息地复杂性仍是常见做法，但对河流水生群落产生积极影响的证据并不一致。在城市集水区的溪流中，河段尺度的栖息地改造和集水区尺度的行动以改善城市雨水径流的干扰状况是常见的管理对策，因此需要更清楚地了解在不同程度的城市影响下栖息地复杂性的影响。我们通过实验评估了木材表面复杂性增加的影响，木材是我们在14条小溪流的18个研究河段中的主要硬质基质，对一系列城市影响下的河流水生大型无脊椎动物群落的影响。表面复杂性增加使大多数分类群的丰度增加，但这种影响在城市溪流中不太明显，部分原因是耐城市雨水影响的物种库减少，部分原因是一些物种对城市程度更高的溪流中复杂性增加的反应较小。总体而言，这些特定分类群的影响导致农村溪流中分类丰富度随着复杂性增加而有小幅度的、不确定的增加，而城市溪流中多样性较低的群落的丰富度没有变化。丰度增加表明随着表面复杂性增加，避难所或资源的可用性增加，而城市溪流中复杂性影响的降低表明，在接收城市雨水径流的更受干扰的环境中，更大表面复杂性提供的任何避难所或资源效果较差。城市程度更高的溪流中敏感分类群的丰度降低以及由此导致的丰富度降低，证实了城市雨水径流是一个强大的环境过滤器，限制了群落组装可用的物种库。在没有集水区尺度退化驱动因素的溪流中恢复栖息地复杂性可能会对河流水生生物群落产生积极效益，但在受城市雨水径流影响的集水区中，这种方法的效果将大大降低。在这种情况下，恢复活动应首先旨在控制更大规模的问题。
