Landscape Ecology Group, Department of Ecology and Environmental Science, Umeå University, Umeå, Sweden.
Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Ecol Appl. 2018 Mar;28(2):587-597. doi: 10.1002/eap.1672. Epub 2018 Feb 20.
Although ecological restoration generally succeeds in increasing physical heterogeneity, many projects fail to enhance biota. Researchers have suggested several possible explanations, including insufficient restoration intensity, or time-lags in ecological responses that prevent detection of significant changes in short-term monitoring programs. This study aims to evaluate whether benthic macroinvertebrate communities responded to an expanded set of stream restoration measures within a study period of one to five years after completion of the restoration project. We studied 10 forest streams in northern Sweden that were channelized in the past for timber floating. Managers subjected six of these streams to habitat restoration, on each of these we selected two reaches, located in close proximity but differing in restoration intensity. In "basic" restored reaches, the restoration managers broke up the channelized banks and returned cobbles and small boulders to the main channel. In "enhanced" restoration reaches, they added additional large wood and boulders to reaches previously subjected to basic restoration, and rehabilitated gravel beds. The remaining four streams were not restored, and thus represent the baseline impacted (channelized) condition. We surveyed stream benthic assemblages before the enhanced restoration (year 2010) and three times afterward between 2011 and 2015. Five years after restoration, macroinvertebrate assemblages at the enhanced restored reaches were more differentiated from channelized conditions than those at basic-restored reaches. This reflected increased relative abundances of the insect orders Ephemeroptera and Trichoptera and the bivalve molluscs Sphaeriidae and decreased relative abundances of Chironomidae (Diptera). Analysis of functional traits provided further insights on the mechanistic explanations driving the recovery, e.g., indicating that the augmented channel retention capacity at enhanced restored reaches favored taxa adapted to slow flow conditions and more effectively retained passive aquatic dispersers. The increased restoration intensity in enhanced restored reaches has resulted in shifts in the composition of benthic macroinvertebrate assemblages, including increases in more sensitive taxa. These shifts became fully apparent five years after the enhanced restoration. Our results emphasize the value of longer-term monitoring to assess ecological responses following restoration, and of undertaking additional restoration as a valuable management option for previously restored sites that failed to achieve biotic recovery.
虽然生态恢复通常成功地增加了物理异质性，但许多项目未能增强生物群。研究人员提出了几种可能的解释，包括恢复强度不足，或者生态响应的时滞阻止了在短期监测计划中检测到重大变化。本研究旨在评估在恢复项目完成后一到五年的研究期间，底栖大型无脊椎动物群落是否对一组扩展的溪流恢复措施做出响应。我们研究了瑞典北部的 10 条森林溪流，这些溪流过去曾用于木材漂流。管理者对其中的 6 条溪流进行了栖息地恢复，在每条溪流中选择了两个接近但恢复强度不同的河段。在“基本”恢复河段，恢复管理者打破了渠道化的河岸，并将鹅卵石和小石块放回主河道。在“增强”恢复河段，他们在以前进行基本恢复的河段上增加了额外的大型木材和石块，并修复了砾石床。其余的 4 条溪流没有得到恢复，因此代表了受影响的基准（渠道化）条件。我们在增强恢复之前（2010 年）以及 2011 年至 2015 年之间的三次调查了溪流底栖生物群。恢复五年后，增强恢复的河段的大型无脊椎动物群落与渠道化条件的差异大于基本恢复的河段。这反映了蜉蝣目和毛翅目昆虫以及双壳类软体动物 Sphaeridae 的相对丰度增加，而摇蚊目（双翅目）的相对丰度降低。功能特征分析提供了进一步的机制解释，例如表明增强的通道保留能力在增强恢复的河段有利于适应缓慢水流条件的类群，并更有效地保留被动水生扩散者。增强恢复的河段增加了恢复强度，导致底栖大型无脊椎动物群落的组成发生变化，包括增加了更敏感的类群。这些变化在增强恢复五年后才完全显现出来。我们的研究结果强调了进行长期监测以评估恢复后生态响应的价值，以及对以前恢复的未能实现生物恢复的地点进行额外恢复作为一种有价值的管理选择的重要性。
