The Nature of Urban Soils and Their Role in Ecological Restoration in Cities

Current and predicted trends indicate that an increasing proportion of the world’s population is living in urban and suburban places. The nature of the urban environment becomes an important factor if we are concerned with the restoration and preservation of biodiversity and ecosystems in and around cities. This article highlights the varied impacts of cities on soils and their implications for restoration planning and expectations of restoration “success.” Urban soils exist in different historical and formational trajectories than their local nonurbanized counterparts due to direct anthropogenic disturbance and indirect environmental impacts from urbanization. Therefore, urban soils often exhibit altered physical, chemical, and biological characteristics in comparison to local nonurbanized soils. Several unique features of urban soils and urban ecosystems pose particular issues for ecological restoration or the improvement of degraded soil conditions in cities. The creation of novel soil types, conditions that promote invasion by non‐natives, the strong influence of past land use on soil properties, and the presence of strong interactions and alternative stable states set up unique difficulties for the restoration of urban soils. Soils in urban restorations are a medium that can be deliberately manipulated to improve site conditions or in the monitoring of soil conditions as indices of ecosystem status. Including an explicit role for strong manipulations of soils in urban ecosystems changes how we approach baselines, management, and reference conditions in urban ecological restoration. With an understanding of urban soil ecological knowledge, we can guide aspects of urban ecological restoration toward successful outcomes.     

城市生态系统修复研究进展

城市生态系统是社会-经济-自然复合生态系统。城市生态系统修复的实质是协调好城市复合生态系统的自然过程、经济过程和社会过程之间的关系,促进复合生态系统的各方面协调高效可持续发展。以城市绿地、城市湿地、城市废弃地三类主要的城市生态空间为对象,论述了城市生态系统修复的研究进展,提出当前城市生态系统修复存在以人工修复技术为主、自然修复不足、机理和量化研究缺乏、理论和应用脱节、管理机制不健全、复合生态系统理论体现不足等问题。梳理了当前城市生态系统修复的研究热点,包括城市生态系统修复机理、城市生态资产与生态系统服务、城市生态系统质量和健康、问题导向的生态修复、面向人类福祉的生态修复、生态修复多学科融贯,以及新方法和新技术的应用等几个方面。提出了城市生态修复与管理的相关对策和建议,可为我国城市生态系统修复的研究和实践提供参考。     

Restoring streams in an urbanizing world

1. The world's population is increasingly urban, and streams and rivers, as the low lying points of the landscape, are especially sensitive to and profoundly impacted by the changes associated with urbanization and suburbanization of catchments. 2. River restoration is an increasingly popular management strategy for improving the physical and ecological conditions of degraded urban streams. In urban catchments, management activities as diverse as stormwater management, bank stabilisation, channel reconfiguration and riparian replanting may be described as river restoration projects. 3. Restoration in urban streams is both more expensive and more difficult than restoration in less densely populated catchments. High property values and finely subdivided land and dense human infrastructure (e.g. roads, sewer lines) limit the spatial extent of urban river restoration options, while stormwaters and the associated sediment and pollutant loads may limit the potential for restoration projects to reverse degradation. 4. To be effective, urban stream restoration efforts must be integrated within broader catchment management strategies. A key scientific and management challenge is to establish criteria for determining when the design options for urban river restoration are so constrained that a return towards reference or pre‐urbanization conditions is not realistic or feasible and when river restoration presents a viable and effective strategy for improving the ecological condition of these degraded ecosystems.     

A conceptual framework for urban ecological restoration and rehabilitation

Urban greenspace has gained considerable attention during the last decades because of its relevance to wildlife conservation, human welfare, and climate change adaptation. Biodiversity loss and ecosystem degradation worldwide require the formation of new concepts of ecological restoration and rehabilitation aimed at improving ecosystem functions, services, and biodiversity conservation in cities. Although relict sites of natural and semi-natural ecosystems can be found in urban areas, environmental conditions and species composition of most urban ecosystems are highly modified, inducing the development of novel and hybrid ecosystems. A consequence of this ecological novelty is the lack of (semi-) natural reference systems available for defining restoration targets and assessing restoration success in urban areas. This hampers the implementation of ecological restoration in cities. In consideration of these challenges, we present a new conceptual framework that provides guidance and support for urban ecological restoration and rehabilitation by formulating restoration targets for different levels of ecological novelty (i.e., historic, hybrid, and novel ecosystems). To facilitate the restoration and rehabilitation of novel urban ecosystems, we recommend using established species-rich and well-functioning urban ecosystems as reference. Such urban reference systems are likely to be present in many cities. Highlighting their value in comparison to degraded ecosystems can stimulate and guide restoration initiatives. As urban restoration approaches must consider local history and site conditions, as well as citizens’ needs, it may also be advisable to focus the restoration of strongly altered urban ecosystems on selected ecosystem functions, services and/or biodiversity values. Ecosystem restoration and rehabilitation in cities can be either relatively inexpensive or costly, but even expensive measures can pay off when they effectively improve ecosystem services such as climate change mitigation or recreation. Successful re‐shaping and re-thinking of urban greenspace by involving citizens and other stakeholders will help to make our cities more sustainable in the future.     

Urban Grassland Restoration: A Neglected Opportunity for Biodiversity Conservation

Urbanization is one of the most severe threats to biodiversity, so why should not we use green space in cities to counteract the biodiversity loss as much as possible? Urban grasslands provide a large number of social, financial, recreational, and environmental ecosystem services but can also support high biodiversity. In this article, I describe the importance of urban grasslands for (local) biodiversity and recommend strengthening restoration ecological research and efforts to optimize these novel ecosystems for conservation purposes. The management intensity of a high proportion of urban grasslands decreased over the last decades. However, species richness of these grasslands is still low, although there is now a great potential for higher plant, but also animal diversity. While communal authorities are interested in cost‐efficient but at the same time biodiversity‐friendly management of urban grasslands, a well‐founded scientific basis for the restoration of urban grassland is still missing. I argue that besides all challenges associated with the restoration of urban habitats we should urgently proceed in the development of appropriate and effective restoration approaches and communicate knowledge gained to urban planners and stakeholders. Widening the scope of restoration ecological research to novel ecosystems such as urban grasslands is one of the most important recent challenges for biodiversity restoration and it gives urban habitats the significance they deserve .     

Range of variability of channel complexity in urban,restored and forested reference streams

Summary 1. Channel complexity is an important ecological property of stream systems and is often targeted for restoration in channelised urban streams. However, channel complexity is rarely defined explicitly, and little research on channel complexity has been conducted in streams in urban catchments that have not been directly channelised by human activities. Therefore, it remains unclear whether restoration of non‐channelised urban streams has improved complexity. 2. We explicitly define channel complexity and use a multimetric approach to provide a comprehensive assessment of complexity in multiple restored, urban and forested streams on the Maryland Coastal Plain and two streams of differing land use in Colorado. We also expand on the Maryland and Colorado results with a literature survey of channel complexity from diverse geographical regions. 3. Many streams draining urban catchments in Maryland had relatively high values of some complexity metrics compared to forested reference streams in Maryland and compared to the values for pristine streams calculated from the literature. This suggests that streams in urban catchments that are not directly manipulated by human activities (e.g. channelisation or piping) may be able to maintain channel structures beneficial for aquatic organisms even when impervious surfaces are the dominant form of land use in the catchment. 4. Restored streams in Maryland had equal or lower values of many complexity metrics compared to streams draining urban catchments in Maryland. This suggests that restoration of streams draining urban catchments did not improve the overall channel complexity. 5. Our results highlight the need to explicitly define and measure the attributes of channel complexity that are targeted during restoration, to determine whether the streams in urban catchments are truly degraded with respect to channel complexity. 6. Combined with recent synthesis work suggesting that biodiversity may not be improved by increasing the channel complexity, these results indicate that targeting catchment processes may prove a more useful approach to restoration than attempting to move channel complexity in streams draining urban catchments towards conditions in forested reference streams.     

生态智慧引导下的太原市棕地修复逻辑与策略

城市生态系统是一个复杂的人工系统,城市经过快速掠夺式的发展已经造成绿地生态空间锐减,水体资源缺乏且污染严重,热岛效应突出和城市棕地面积大且污染严重等一系列生态问题。以资源枯竭型城市内大量存在的棕地为研究对象,认为城市棕地的修复需要生态智慧的引导,在建立生态智慧引导的城市棕地修复逻辑和框架的基础上,结合太原市棕地生态修复实践,建立从棕地安全性修复、棕地功能修复和棕地景观修复的综合修复框架,提出分期分类多元化再生,分类利用城市功能活化,去棕还绿抗污染植物配置棕地修复的生态智慧策略。     

Promoting social and environmental justice to support Indigenous partnerships in urban ecosystem restoration

Urban ecological restoration typically employs western science approaches to restore degraded ecosystems. As yet, few restoration groups acknowledge the history of these degraded urban sites, despite connections, past and present, that root Indigenous Peoples (and others) in these lands. Here, we promote partnership with Indigenous communities from project inception and present two successful case studies from Aotearoa New Zealand. We specifically note that partnering and building relationships with Indigenous communities in restoration efforts require recognition of power inequalities and injustices. We consider success to include both restoration of ecological function and biodiversity and reconnection of all communities to urban ecosystems.     

Urban and rural river restoration in France: a typology

River restoration (RR) is widely practiced in both rural and urban contexts by combining various goals and measures. The theoretical discourse on RR not yet adequately reflects this breadth of restoration practice. In this study, we investigated 110 French RR projects implemented between 1980 and 2015. We analyzed projects considering eight key design features, main project motivation, restoration goals, project dates, costs, size, funding, river annual discharge, and implemented evaluation procedures. The study (1) provides a detailed account of the French RR effort, (2) compares restoration efforts in urban and rural contexts, and (3) establishes a RR project typology. The results also show that urban RR comprises a wider range of goals and measures than its rural counterpart, includes restoration of riparian habitats, and integrates ecological and social goals. A hierarchical multiple factor analysis yielded five types of projects, Fish RR (14% of the urban and 53% of the rural projects), Blue RR (4%, 7%), Water Framework Directive RR (36%, 40%), Flood protection RR (14%, 0%), and Human RR (32%, 0%). We suggest that the restoration community needs databases that use a project typology as developed in this study. This approach would take into account the multiple facets of RR projects, enabling more transparency into their communication and allow more suitable project comparisons.     

Comparing the Fish and Benthic Macroinvertebrate Diversity of Restored Urban Streams to Reference Streams

Urbanization is associated with substantial losses to stream biological diversity throughout the United States' mid‐Atlantic. Stream restoration has been used to improve stream conditions and, in part, to ameliorate these losses. However, the relationship between restoration and recovery of biological diversity is unclear. Our objective was to critically examine the efficacy of urban stream restorations with regard to biological diversity. We compared restored urban streams to urban nonrestored, nonurban, and reference (minimally degraded) streams using five measures each of fish and benthic macroinvertebrate diversity. Both multivariate and univariate statistical analyses show biological diversity of restored urban streams to be similar to nonrestored urban streams and lower than nonurban and reference streams. Restored urban sites showed no apparent increase in biological diversity through time, while diversity decreased at two of the reference streams coincident with increased urban development within their catchments. Our results indicate that restoration approaches commonly used regionally as in these urban streams are not leading to recovery of native stream biodiversity. Evidence from several sources indicates a need for dramatic changes in restoration approach, and we argue for a watershed‐scale focus including protection of the least impacted streams and adopting other land‐based actions within the watershed where possible.     

城市野境： 城市区域中野性自然的保护与营造

城市野境是城市内部或周边区域中自然过程占主导的土地,其中人类开发和控制程度相对较低,允许在一定程度上发生自然演替和生态过程,各类野生生物能够与人类繁荣共存。城市野境在重新连接人与自然、促进人类身心健康、保护生物多样性、维持生态系统服务方面具有重要和独特的价值。基于文献综述与案例研究,提出并阐释了保护与营造城市野境的 4 种途径,包括保护、修复、设计与融合,即在城市保护地中保护野性自然、再野化部分城市区域、在城市公园中营造类荒野景观以及在城市空间中系统性融入野性自然。建议在中国城市规划与城市设计中,融入野性自然保护与修复的理念,进一步探索城市野境保护与营造的理论与方法。     

国内外主要湾区生态系统特征、修复理论与技术模式

通过总结粤港澳大湾区、东京湾区和旧金山湾区等国内外主要湾区的生态系统特征、生态修复理论和实践研究进展,在辨析生态修复概念内涵的基础上,基于Meta-Analysis及综合分析方法,分析了生态系统退化机制及驱动因子,归纳总结湾区生态修复的主要理论基础、技术模式及案例。结果表明:(1)国内外三大主要湾区的生态系统特征为森林占比最高,其次是农田和草地占比,城镇占比第三。森林一般分布在湾区外围,城镇分布在湾区内核河口三角洲附近。(2)湾区生态修复理论包括以恢复生态学、景观生态学和复合生态系统生态学为基础的三种修复理论,生态修复的类别分为补救修复、改善修复、生态恢复和复垦等。(3)湾区生态修复技术模式包括主动修复、被动修复和重建等三类技术模式。在总结梳理生态修复理论和技术模式的基础上,结合当前国内生态修复存在问题,本文提出我国和广东省开展生态修复实践的建议和展望,以期为粤港澳大湾区生态修复提供一定的理论指导。     

Comparison of Designed Channel Restoration and Riparian Buffer Restoration Effects on Riparian Soils

Stream restoration is often employed in efforts to stabilize eroding channel banks. Banks are stabilized through a designed channel approach, which involves grading and armoring of stream banks using heavy machinery, or alternatively through planting of seedlings and saplings to establish forested riparian buffers. We hypothesized that designed channel restoration would have detrimental impacts on riparian soils but that soils would recover over time, and we hypothesized that riparian buffer restoration would not impact riparian soils. We tested these hypotheses by comparing soil attributes (bulk density, soil organic matter, and root biomass) at reaches that had undergone designed channel and riparian buffer restoration in different years (project ages ranged from 2 to 16 years) to paired urban (unrestored) control reaches. Soil properties in sub‐surface soil layers (10–20 and 20–30 cm depth) at both recent (<10 years old) and older (>10 years old) designed channel reaches differed significantly from paired urban control soils; bulk density was higher and root biomass lower in manipulated reaches compared to urban control reaches. At many designed channel reaches, bulk density exceeded values known to restrict root growth. These results indicate that compaction and disturbance of riparian soils may be a significant unintended consequence of designed channel restoration and can persist for at least a decade. In contrast, we found no significant differences in soil properties between riparian buffer restoration reaches and urban control reaches. Thus, the results indicate that riparian buffer restoration is a more ecologically favorable method than designed channel restoration for bank stabilization.     

GI引导下的采煤塌陷地生态恢复优先级评价

生态恢复优先级评价是恢复生态学研究的热点之一,而退化生态系统被恢复为何种类型是确定生态恢复优先级的前提和重点。以徐州市为研究区,将城市绿色基础设施(GI)作为塌陷地生态恢复的目标,在GIS技术支撑下,从塌陷斑块恢复为GI的适宜性及其对维持GI景观连接度的重要性两个方面,综合评价了采煤塌陷地生态恢复优先级。研究结果表明,徐州市超过半数的采煤塌陷斑块具有较高的GI生态适宜性,相对集中在5个片区;各塌陷斑块维持景观连接度的重要性分布不均匀,贾汪片区中部及北部塌陷斑块对维持景观连接度的作用非常显著;二者叠加后各塌陷斑块的综合适宜度具有明显差异,将其划分为5个生态恢复优先等级,较高优先等级分布于贾汪片区中部、董庄片区北部、庞庄西片区中部,建议将其纳入城市绿色基础设施予以优先恢复并立法保护。     

城市绿色空间研究进展与展望

在总结国内外城市绿色空间概念和类型的基础上,从城乡边缘区规划保育、自然区与乡土物种恢复保护、绿色廊道恢复规划、生物多样性保护以及绿色空间结构-功能研究和管理政策等6个方面,对近年来城市绿色空间的研究状况进行了分析,探讨国内外城市绿色空间基础研究与实践的不同之处,并提出未来城市绿色空间研究的主要方向,以期对我国未来城市绿色空间研究与构建有所启示.     

Assessing the impact of revegetation and weed control on urban sensitive bird species

Nature in cities is concentrated in urban green spaces, which are key areas for urban biodiversity and also important areas to connect people with nature. To conserve urban biodiversity within these natural refugia, habitat restoration such as weed control and revegetation is often implemented. These actions are expected to benefit biodiversity, although species known to be affected by urbanization may not be interacting with restoration in the ways we anticipate. In this study, we use a case study to explore how urban restoration activities impact different bird species. Birds were grouped into urban sensitivity categories and species abundance, and richness was then calculated using a hierarchical species community model for individual species responses, with “urban class” used as the hierarchical parameter. We highlight variable responses of birds to revegetation and weed control based on their level of urban sensitivity. Revegetation of open grassy areas delivers significant bird conservation outcomes, but the effects of weed control are neutral or in some cases negative. Specifically, the species most reliant on remnant vegetation in cities seem to remain stable or decline in abundance in areas with weed control, which we suspect is the result of a simplification of the understorey. The literature reports mixed benefits of weed control between taxa and between locations. We recommend, in our case study site, that weed control be implemented in concert with replanting of native vegetation to provide the understory structure preferred by urban sensitive birds. Understanding the impacts of revegetation and weed control on different bird species is important information for practitioners to make restoration decisions about the allocation of funds for conservation action. This new knowledge can be used both for threatened species and invasive species management.     

新时期我国国土空间生态修复理念与模式探讨

国土空间生态修复以地理学、景观生态学理论为基础,是推进生态文明、建设美丽中国的重要举措。我国国土空间生态修复呈现理论体系多学科化、工作模式多元化、技术方法融合化、实践探索多样化的特征,工作总体成效显著与任务艰巨并存。本文基于国土空间生态修复的新挑战,对国土空间生态修复研究的总体框架和技术路径、区域国土空间生态修复的工作机制与模式、国土空间生态修复的内容体系和技术标准进行综述。新时期,我国国土空间生态修复顶层设计应重点围绕工作体系、业务边界和制度体系3项内容,明确各类业务流程的职责边界,从理论、制度、工程、技术全域视角实现工作全链条闭合管理。乡村聚落区、城镇建成区、工矿聚集区、生态功能区、蓝色海洋区是区域尺度国土空间的5大组成要素,分别对应全域土地综合整治、城市更新与城市双修、矿山地质环境修复治理、山水林田湖草系统修复、蓝色海湾修复整治5种差别化生态修复模式。应综合运用“三个集成”(信息、技术、流程)思维,构建一套涵盖调查监测评价、国土空间规划、工程项目实施、工程项目验收、生态系统监测评价一体化的区域国土空间生态修复工作模式。     

Urban Options for Psychological Restoration: Common Strategies in Everyday Situations

Objectives

Given the need for knowledge on the restorative potential of urban settings, we sought to estimate the effects of personal and contextual factors on preferences and restoration likelihood assessments for different urban activities-in-environments. We also sought to study the generality of these effects across different countries.

Methods

We conducted a true experiment with convenience samples of university students in the Netherlands (n = 80), Sweden (n = 100), and the USA (n = 316). In each country, the experiment had a mixed design with activities-in-environments (sitting in a park, sitting in a cafe, walking in a shopping mall, walking along a busy street) manipulated within-subjects and the need for restoration (attentional fatigue, no attentional fatigue) and immediate social context (in company, alone) manipulated between-subjects. The manipulations relied on previously tested scenarios describing everyday situations that participants were instructed to remember and imagine themselves being in. For each imagined situation (activity-in-environment with antecedent fatigue condition and immediate social context), subjects provided two criterion measures: general preference and the likelihood of achieving psychological restoration.

Results

The settings received different preference and restoration likelihood ratings as expected, affirming that a busy street, often used in comparisons with natural settings, is not representative of the restorative potential of urban settings. Being with a close friend and attentional fatigue both moderated ratings for specific settings. Findings of additional moderation by country of residence caution against broad generalizations regarding preferences for and the expected restorative effects of different urban settings.

Conclusions

Preferences and restoration likelihood ratings for urban activity-environment combinations are subject to multiple personal and contextual determinants, including level of attentional fatigue, being alone versus in company, and broader aspects of the urban context that vary across cities and countries. Claims regarding a lack of restorative quality in urban environments are problematic.     

珠江三角洲城市群生态安全保障技术研究

近年来,在工业化、城镇化迅速推进和人口急剧增长的同时,珠三角城市群正面临严重的现代城市生态问题。生态安全问题已成为珠三角地区率先全面建成小康社会的重大制约瓶颈,对该地区经济社会的可持续发展构成了严重的威胁。"珠江三角洲城市群生态安全保障技术"项目将围绕脆弱生态修复与保护这一科技需求,对珠三角城市群复合生态系统进行综合研究。项目将针对内部互动复杂、空间组织紧凑、经济关联密切的城市群复合生态系统,开展城市群生态基底核算与健康诊断、城市群代谢模拟与生态风险预测预警技术、城市群生态安全格局网络设计及生态安全保障技术、城市群生态景观重建与生态空间修复技术、濒海城市群受损生境修复与生态安全保障技术以及城市群生态安全调控技术集成及协同监管平台构建与示范等六方面的研究。项目将为珠三角城市群生态问题的识别、评估与调控提供有效的理论基础、方法体系及技术示范,由之将为保障该城市群的生态安全提供科学支持,并带来显著的社会、经济与生态效益。     

珠三角城市群生态空间分区方法与管控对策

生态空间管控是维护区域生态安全,解决区域生态供需矛盾的重要手段。生态空间分区一直是生态管控的热点问题,对促进城市群可持续发展具有重要意义。以珠三角城市群为例,基于政策目标、民众需求、专家知识等方面综合构建评价体系,开展了基于生态空间质量和生态系统健康评价的生态空间分区的探索研究。结果表明：珠三角城市群生态空间约占城市群面积的82.8%,生态空间质量好,但生态系统健康水平低。城市尺度肇庆市、深圳市生态空间质量较高,珠海市、中山市生态空间质量较低;惠州市、肇庆市生态系统健康水平较高,佛山市、中山市生态系统健康水平较低。综合生态空间质量和生态系统健康,区域尺度将城市群生态空间分为重点保护区、重点修复区、潜在修复区和生态保育区。重点保护区占生态空间总面积的10.1%,是区域生态源地,应实行最严格的环境保护制度,划定生态保护红线和自然保护地,加强生态建设和生物多样性保护,并加强生态连通性建设,提升区域整体生态系统服务;重点修复区占生态空间总面积的21.6%,以生态修复,实施生态治理工程,推进生态产业为主;潜在修复区占生态空间总面积的13.1%,以保护优先、自然恢复为主,对生态空间进行全面的养护,保护和提升品质,重点提升生态系统服务;生态保育区占生态空间总面积的55.2%,重点实施生态廊道建设,同时加强区域高标准农田建设,在保护生态空间的基础上合理开展生产建设活动。对生态空间分区管控的研究可方便决策者对生态修复空间和生态保护空间进行识别和分类管理,有效指导国土空间规划和区域生态环境管理体系的完善。