Recovery of lotic communities and ecosystems from disturbance—A narrative review of case studies

We present a narrative account of case studies of the recovery of flowing water systems from disturbance, focusing on the investigators' conclusions about recovery time and the factors contributing to recovery. We restrict our attention to case studies in which the recovery of some biological property of the system has been examined, excluding those that deal only with physical or chemical properties. Although natural processes and rates of recovery are emphasized, studies of reclamation or restoration of damaged ecosystems are included where they contribute to an understanding of recovery processes. For the majority of studies examined, the systems recovered quite rapidly. The most commonly cited reasons for short recovery times were: (1) life history characteristics that allowed rapid recolonization and repopulation of the affected areas, (2) the availability and accessibility of unaffected up-stream and downstream areas and internal refugia to serve as sources of organisms for repopulation, (3) the high flushing rates of lotic systems that allowed them to quickly dilute or replace polluted waters, and (4) the fact that lotic systems are naturally subjected to a variety of disturbances and the biota have evolved life history characteristics that favor flexibility or adaptability. In general, longer recovery times were observed in disturbances, such as channelization, that resulted in alterations to physical conditions. This review also indicates that much of our knowledge of recovery in lotic ecosystems is fragmented and uncoordinated. In addition to establishing the bounds of recovery time, our review identifies some research gaps that need to be filled.     

A “justice” reading of the trans-national struggle of the people displaced by the Merowe Dam

ABSTRACT

This paper applies a “justice” lens to the struggle of the people displaced by the Merowe Dam in northern Sudan. Application of distributive, procedural, and representational aspects of justice exposes the dissatisfaction of the affected people with the government’s offer and execution of compensation. Consideration of social justice and the utility of norms in trans-national activism brings into sharp focus the difference in interests, and abilities of the many actors involved, and highlights the government’s tactics to divide the communities, and the social divisions sown. As the struggle develops, justice claims are seen to change towards less material issues, suggesting that an expanded and dynamic conception of justice is more helpful than narrow or time-bound conceptions. The findings are of relevance to communities facing possible displacement from dams planned nearby, not least of all for the insight provided on the effectiveness of different tactics in the struggle.     

“三江源”地区主要生态环境问题与对策

长江、黄河、澜沧江河源地区地处青藏高原腹地,是我国江河中、下游和周边地区生态环境安全和区域可持续发展的生态屏障。近年来,由于自然因素与不合理的人类活动影响,“三江源”地区生态环境不断恶化,不仅严重影响和制约了当地各民族生存与发展,而且还危及中下游地区的经济与社会的可持续发展。论文分析了三江源地区所处的生态环境地位,揭示了该区生态环境存在的问题与症结,提出了三江源地区生态环境保护与建设的对策建议:①三江源自然保护区的建设必须重视科学研究,制定高水平的科学规划;②必须采取有力措施妥善安置核心区的移民;③建立科学研究基地,依靠科技创新和高新适用技术的引进和推广应用,促进当地社会经济的发展和生态环境建设;④加强生态环境建设,走可持续发展的道路;⑤加强鼠害治理,促进草场生态系统的恢复;⑥建立上、中、下游利益补偿机制,促进江河源区生态环境事业的良性发展。     

水电工程干扰下澜沧江典型段的水温时空特征

以澜沧江流域漫湾库尾至大朝山坝下的水电工程干扰典型段为研究区域,利用1978～2005年建坝前后的水温实测资料,采用相关分析、线性回归的方法分析表层水温、下泄水温的时空分布特征.结果表明,水电工程建设后库区蓄水对表层水温有着明显的增温效应,坝前表层水温仅5～8月低于气温,其余所有月份坝前表层水温均高于建坝前的天然表层水温,时间分异性减弱.库区出水温度一般冬季(干季)高于气温和天然表层水温,而夏季(雨季)则相反,与天然水温和气温的变化趋势有2个月的滞后性.从库尾到坝前,表层水温与天然气温逐渐接近,水温/气温比与距离大坝距离之间存在正相关关系,漫湾库区下泄水对大朝山库区的水温具有一定的累积效应.本研究结果表明水电工程对澜沧江典型河段的水温时空分布存在显著效应.     

“三江源”地区主要生态环境问题与对策

长江、黄河、澜沧江河源地区地处青藏高原腹地,是我国江河中、下游和周边地区生态环境安全和区域可持续发展的生态屏障。近年来,由于自然因素与不合理的人类活动影响,“三江源”地区生态环境不断恶化,不仅严重影响和制约了当地各民族生存与发展,而且还危及中下游地区的经济与社会的可持续发展。论文分析了三江源地区所处的生态环境地位,揭示了该区生态环境存在的问题与症结,提出了三江源地区生态环境保护与建设的对策建议:①三江源自然保护区的建设必须重视科学研究,制定高水平的科学规划;②必须采取有力措施妥善安置核心区的移民;③建立科学研究基地,依靠科技创新和高新适用技术的引进和推广应用,促进当地社会经济的发展和生态环境建设;④加强生态环境建设,走可持续发展的道路;⑤加强鼠害治理,促进草场生态系统的恢复;⑥建立上、中、下游利益补偿机制,促进江河源区生态环境事业的良性发展。     

三江流域土地覆被／土地利用与生态系统功能关系研究

三江流域具有特殊严酷的自然环境和相对落后的经济条件,本区域的生态环境极度脆弱,不但限制了本区域的经济发展,还严重威胁着中下游地区的安全。但是长期的过量森林砍伐,落后的农业生产方式,导致本地区的生态功能退化严重,恢复重建异常困难。因此如何改变过去的生产方式,充分发挥土地生产潜力,提高人民生活,促进社会经济持续发展,已成为国内国际关注的重点。本文运用土地生态学和景观生态学原理,对三江流域土地覆被／土地利用与生态系统功能关系进行了探讨,在土地利用方面提出了减少耕地,实施退耕还林或还草;对干暖河谷灌丛生态系统和寒漠生态系统要以保护为前提,减少人为活动影响,发挥生态系统自身调节能力,使之向健康方向发展,对森林生态系统和高寒草甸生态系统要发挥其生态功能和经济功能。最终实现土地资源的可持续利用,取得最大的社会、生态、经济效益。     

引江入湖修复城市内湖方案的初步探索

文章采用引水换水方案,通过对湖北黄石磁湖水和长江水的水质监测,在实验室条件下,采用静态浸泡实验,模拟换水工程,测定水质基本指标的变化情况,探讨了引江入湖修复城市内湖生态环境方案的可行性。结论认为:采用江水湖水比例为1.5∶1,秋冬季节引水较为适宜;考虑磁湖内源污染严重,单纯的引水对湖水水质改善难以发挥最大的环境和经济效益,可以采取有效的内源污染治理方案和引水方案并重对磁湖进行生态修复。     

干堆尾矿子坝结构参数的稳定性响应规律研究

针对干堆尾矿库设计时缺乏子坝结构参数取值依据的实际困难,采用数值试验和工程实证相结合的方法,系统研究了干堆尾矿库坝体结构参数对稳定性的响应规律,提出干堆尾矿库子坝结构参数选取方法。结果表明:堆坝安全系数Fs随子坝高h降低整体呈先增后减的变化规律,峰值为最佳子坝高,其值与堆积坝总高呈正相关,通常取值为堆积坝总高的1/5-1/7;安全系数Fs与马道宽d呈正相关,推荐在3-6m范围取值。     

An exploration of the relationships betweenmacroinvertebrate community composition and physical andchemical habitat characteristics in farm dams

Recently, Australian interest in farm dams has focused on rates of harvest of surface waters (runoff), and the impact this has on nearby natural systems. Little research has been directed towards the role of these artificial water bodies in sustaining biological reserves within the wider ecosystem. Macroinvertebrate communities in three farm dams in the Central Tablelands of New South Wales were surveyed, and water quality variables were correlated with species richness and abundance. Community responses to habitat factors including sediment depth, stock use, vegetation and debris were also examined. Communities were described at several taxonomic levels in addition to allocation to trophic groups and primary functional feeding groups.Species richness and abundance of communities were found to vary between dams and between habitat types within dams. The extent of these differences was decreased when communities were described by either trophic status or functional feeding mechanisms. Habitats were influenced by water quality and by physical features of the habitat, with the two factors interacting to define equilibrium conditions. Localised conditions resulted in different macroinvertebrate communities. Physicochemical parameters that correlated most closely with communities included light penetration, chlorophyll-a and conductivity. Habitat factors that were most frequently linked with communities were sediment depth and canopy cover, with localised disturbances related to stock use affecting feeding groups rather than specific taxa.One of the major problems associated with increasing modification of landscapes by agriculture or urbanisation is the fragmentation of undisturbed habitats. Creation of joint aquatic and woodland habitats enhances biodiversity corridors. The recognition of the potential for farm dams as reservoirs of biodiversity and development of management practices that optimise this neglected biodiversity reserve may have much wider benefits biologically, aesthetically and productively.