Department of Health and Environmental Sciences, Xi'an Jiaotong-Liverpool University, Suzhou, Jiangsu 215123, China; School of Environmental Sciences, University of Liverpool, Liverpool L69 3GP, UK; Zhejiang Institute of Research and Innovation, The University of Hong Kong, Hangzhou, Zhejiang 311305, China.
Department of Landscape Architecture, Gold Mantis School of Architecture, Soochow University, Suzhou, Jiangsu 215123, China.
Sci Total Environ. 2020 Nov 15;743:140583. doi: 10.1016/j.scitotenv.2020.140583. Epub 2020 Jul 4.
Ecological restoration of freshwater ecosystems is now being implemented to mitigate anthropogenic disruption. Most emphasis is placed on assessing physico-chemical and hydromorphological properties to monitor restoration progress. However, less is known about the structural integrity and ecosystem health of aquatic ecosystems. In particular, little is known about how ecosystem function changes following river habitat restoration, especially in China. Leaf litter decomposition can be used as an indicator of stream ecosystem integrity. Therefore, the leaf breakdown rate was measured to assess the ecosystem function of restored rivers. By comparing leaf breakdown rates in urban rivers undergoing habitat restoration with that in degraded urban rivers and rivers in forested areas (i.e., reference conditions), we aimed to determine: (i) how habitat restoration affected leaf litter decomposition? (ii) the relationship between leaf litter decomposition to both environmental (habitat and physico-chemical variables) and biological factors (benthic communities), and (iii) identify the factors that contribute most to the variance in leaf litter breakdown rates. The results demonstrated a significant increase in leaf breakdown rate (120% in summer and 28% in winter) in the restored rivers compared to the degraded rivers. All environmental and biotic factors evaluated contributed synergistically to the differences in leaf litter decomposition among the three river types. The role of macroinvertebrates, mainly shredders, appeared to be particularly important, contributing 52% (summer) and 33% (winter) to the variance in decomposition, followed by habitat characteristics (e.g. substrate diversity, water velocity; 17% in summer, 29% in winter), physico-chemical variables (e.g. nutrient and organic pollutants; 11% in summer, 1% in winter) and biofilm bacteria (0% in summer, 15% in winter). Habitat restoration positively affected the structure and function of the previously degraded streams. Knowledge on controlling variables and their attribution to changes of ecosystem functioning provides guidance to assist the future planning of ecological restoration strategies.
淡水生态系统的生态恢复目前正在实施，以减轻人为干扰。大多数重点是评估物理化学和水形态学特性，以监测恢复进展。然而，水生生态系统的结构完整性和生态健康知之甚少。特别是，对于河流栖息地恢复后生态系统功能如何变化，知之甚少，尤其是在中国。叶凋落物分解可用作溪流生态系统完整性的指标。因此，测量了叶分解率以评估恢复河流的生态系统功能。通过比较正在进行栖息地恢复的城市河流、退化的城市河流和森林地区（即参考条件）的叶分解率，我们旨在确定：（i）栖息地恢复如何影响叶凋落物分解？（ii）叶分解与环境（栖息地和物理化学变量）和生物因素（底栖群落）之间的关系，以及（iii）确定对叶分解率变化贡献最大的因素。结果表明，与退化河流相比，恢复河流的叶分解率显著增加（夏季增加 120%，冬季增加 28%）。评估的所有环境和生物因素协同作用，导致三种河流类型之间叶凋落物分解的差异。大型无脊椎动物，主要是碎食者的作用似乎尤为重要，对分解的变异贡献了 52%（夏季）和 33%（冬季），其次是栖息地特征（如基质多样性、水流；夏季 17%，冬季 29%）、物理化学变量（如营养物和有机污染物；夏季 11%，冬季 1%）和生物膜细菌（夏季 0%，冬季 15%）。栖息地恢复对以前退化的溪流的结构和功能产生了积极影响。对控制变量的了解及其对生态系统功能变化的归因，为协助未来生态恢复策略的规划提供了指导。
