Integrating ecology with hydromorphology: a priority for river science and management

• 1. The assessment of links between ecology and physical habitat has become a major issue in river research and management. Key drivers include concerns about the conservation implications of human modifications (e.g. abstraction, climate change) and the explicit need to understand the ecological importance of hydromorphology as prescribed by the EU's Water Framework Directive. Efforts are focusing on the need to develop ‘eco‐hydromorphology’ at the interface between ecology, hydrology and fluvial geomorphology. Here, the scope of this emerging field is defined, some research and development issues are suggested, and a path for development is sketched out.
• 2. In the short term, major research priorities are to use existing literature or data better to identify patterns among organisms, ecological functions and river hydromorphological character. Another early priority is to identify model systems or organisms to act as research foci. In the medium term, the investigation of pattern–processes linkages, spatial structuring, scaling relationships and system dynamics will advance mechanistic understanding. The effects of climate change, abstraction and river regulation, eco‐hydromorphic resistance/resilience, and responses to environmental disturbances are likely to be management priorities. Large‐scale catchment projects, in both rural and urban locations, should be promoted to concentrate collaborative efforts, to attract financial support and to raise the profile of eco‐hydromorphology.
• 3. Eco‐hydromorphological expertise is currently fragmented across the main contributory disciplines (ecology, hydrology, geomorphology, flood risk management, civil engineering), potentially restricting research and development. This is paradoxical given the shared vision across these fields for effective river management based on good science with social impact. A range of approaches is advocated to build sufficient, integrated capacity that will deliver science of real management value over the coming decades.

Copyright © 2007 John Wiley & Sons, Ltd.     

Freshwater mussel abundance predicts biodiversity in UK lowland rivers

• 1. Indicator taxa are widely used as a valuable tool in the assessment of freshwater biodiversity. However, this approach to identifying sites of conservation priority requires surveyors to possess expert taxonomic knowledge. Furthermore, sorting and microscopic examination of material can present logistical and financial constraints.
• 2. Comparisons were made between the taxon richness and the density of freshwater mussels (Bivalvia: Unionidae) from 30 sites in seven UK lowland rivers, ranging from ca 3 m to 50 m width and ca 0.5 m to 4 m depth. Where mussels occurred, taxon richness of other invertebrates was strongly correlated with both mussel density and mussel biomass. Overall mussel density was a better predictor of taxon richness than the density of any individual mussel species.
• 3. It is suggested that this association arises from the ‘keystone’ role that mussels play in many freshwater ecosystems. Local biota can benefit from the mussels' filtration, excretion, biodeposition and physical presence.
• 4. Using mussel abundance as a surrogate provides a rapid and straightforward alternative to conventional methods of assessing freshwater biodiversity. No expert knowledge is required and any standardized sampling technique can be used. Freshwater mussels are found throughout the world's lentic and lotic fresh waters and this approach therefore has the potential for widespread utility, especially where rapid comparisons of biodiversity are required between biogeographically similar regions. In addition, the results highlight the ecosystem‐level consequences of allowing the global decline of freshwater mussels to remain unchecked.

Copyright © 2007 John Wiley & Sons, Ltd.     

A simple method for assessing minimum flows in regulated rivers: the case of sea lamprey reproduction

• 1. The sea lamprey (Petromyzon marinus) is an anadromous species that occurs in some large Iberian rivers, such as the Tagus, and their tributaries. The sea lamprey populations of the River Tagus are threatened by habitat loss and overexploitation, which means that conservation measures, including maintenance of the spawning grounds, are urgent. Habitat loss is mainly due to hydroelectric and flood‐control dams that have affected the migration and spawning habitats of anadromous species. The main objective of this study was to use a simple, cost‐effective method to assess a minimum instream flow for the regulated River Tagus. The method used was based on the wetted perimeter–discharge relationship, but accounted for the habitat requirements of spawning sea lampreys.
• 2. In 1998, a habitat survey was conducted along a 30 km segment of the River Tagus downstream from Belver Dam (the first impassable obstacle for fish movements), a stretch that includes potential habitats for spawning sea lampreys. Four spawning areas were identified, and in each one a representative reach was selected along which to collect elevation and geo‐positional data. For a range of flows from 0 to 50 m³ s^?1, hydraulic modelling and studies of spawning habitat availability were conducted, both for each reach and for the total wetted area of the four reaches.
• 3. The availability of spawning habitat was limited by flow. Results showed that the present minimum flow downstream from Belver Dam (8 m³ s^?1) is insufficient to ensure suitable habitat conditions in a significant part of the segment studied; gains in wetted usable area were more substantial with discharges of up to 20 m³ s^?1, and thus a minimum flow of 10–20 m³ s^?1 was recommended. Potential spawning habitat could be improved by increasing instream flow to at least 50 m³ s^?1. The impacts of the Belver release regime on anadromous species are discussed and a more ‘ecologically oriented’ form of water management is suggested

. Copyright © 2004 John Wiley & Sons, Ltd.     

青浦区重固镇美丽河湖专项规划研究

介绍了重固镇水系现状及存在问题,以提高区域防洪排涝、水资源调控能力、河湖自净能力和改善滨湖环境景观品质为目标,阐述了开展美丽河湖规划的必要性,并对美丽河湖规划的重要因素进行分析研究.     

刈割对江河源区混播草地牧草产量及品质的影响

在江河源区"黑土型"退化草地上用垂穗披碱草Elymus nutans+冷地早熟禾Poa crymophila+中华羊茅Festuca sinensis+碱茅Puccinellia tenuiflora混播建植栽培草地,自生长第2年起连续2年于7月26日-10月6日进行间隔10d的刈割试验。结果表明:2龄草地8月26日刈割牧草鲜草产量最高,为31933kg/hm2,3龄草地8月16日最高,为9520kg/hm2。营养物质的测定表明,8月16日刈割牧草粗蛋白产量最高,2龄为5683kg/hm2,3龄为2189kg/hm2。研究得出8月16-26日是该地区多年生栽培草地的最佳收割时期。     

三江源区高寒草甸湿地植被退化与土壤有机碳损失

人为活动影响下陆地生态系统退化对于土壤碳库损失的影响规模是当前全球变化研究的热点。在青海省三江源区选择了8个高寒草甸典型样区,划分4种不同退化程度样地（原生植被、轻度退化、重度退化、极度退化）,收割法采集地上部植物生物量,10cm等深度采集表土土壤样品,分析了地上生物量、可食牧草生物量以及土壤有机碳含量变化。结果表明,随着退化程度的加剧,地上生物量和饲草生物量均表现强烈下降的趋势,但后者的下降幅度更大,在极度退化下损失达99％。研究区内高寒湿地土壤的表土有机碳含量出现极大的变异性,随退化程度的加剧而呈显著下降。与原生植被下相比,轻度退化、重度退化和极度退化下0-30cm土壤有机碳含量分别平均降低了25％、44％和52％。这种损失固然与地上部生物量下降有关,有机碳分层系数显示土壤侵蚀也是重要因素。估计退化下土壤有机碳平均下降36tC·hm^-2,累积退化下表土有机碳损失可能在200TgC以上,保护高寒草甸生态系统,对于三江源区土壤的畜牧业可持续发展和我国陆地生态系统碳库具有极重要的意义。     

三江源区不同年限黑土滩人工草地植被特征

以三江源区不同建植年限黑土滩人工草地(1、3、7、12、17、21和24龄)及其周边黑土滩(CK)为对象,从植被群落结构、生物量、物种多样性角度,探究三江源区黑土滩人工草地植被变化特征及适宜利用年限,为黑土滩人工草地的合理利用提供理论依据。结果表明：随建植年限增加,人工草地草层的高度和盖度及地上生物量均呈增加趋势,且人工草地比CK高;人工草地的禾本科高度、盖度、地上生物量、地下生物量均高于莎草科、豆科和杂类草,CK样地杂类草高于其他经济类群;各建植年限人工草地优势种和伴生种分别为垂穗披碱草(Elymus nutans)和青海冷地早熟禾(Poa crymophila),且其重要值均随建植年限增加呈逐渐增加趋势;各经济类群物种多样性指数均呈波动式增加趋势,建植3 a人工草地的植物香农维纳指数和均匀度指数最低,分别为0.66、0.48,建植21 a时最高;在植物NMDS分析表明,建植24 a、建植21 a和建植12 a的人工草地与CK样地无重合部分,其植被群落差异度很大。研究得知：建植21 a的黑土滩人工草地群落多样性指数显著高于其他建植年限的人工草地,与黑土滩退化草地相似度最小,群落组成相...     

干旱河谷地区退耕还林调查与生态还林分析

退耕还林工作全面展开已经有4~5年,其执行效果如何?如何及时总结退耕还林中存在的问题和经验进行更好的退耕还林决策呢?利用遥感和地理信息系统技术结合采访调查,及时的、客观反映了退耕还林的执行情况。本文以长江上游生态脆弱区——川藏边缘的横断山区X县为例,应用“3S”技术对退耕还林的成果进行了监测,得出:由于种种原因,该地区退耕还林中可能上报的退耕面积不实,超出实际退耕面积;耕地中很大比例的坡度小于25o的耕地纳入到退耕地中。研究也分析了退耕还林对当地社会、经济等影响,调查和有关研究证实,大面积退耕还林使该地区财政收入大比例较少,农民对国家的补贴依赖性强,一旦停止钱粮补助,农民将失去生活来源,很可能导致毁林复耕。多数农户强烈表达了希望延长粮食补助的愿望,本研究认为经济补偿机制的关键应该放在如何调动农民调整产业结构和发展后续产业的积极性上,否则再长时间的连续补偿也无济于事。对已经大面积退耕的区域,加紧发展后续产业和产业结构调整势在必行,对正在计划退耕的地区,应该将退耕还林作为一个系统工程考虑,退耕还林应该是一个长期的、逐步实施的过程,必须综合各种原则和因素、分清楚轻重缓急,一步步实施,相应的经济补偿机制也需要调整。     

阿尔泰山采金矿区植被恢复效果初探

以阿尔泰山两河源采金废弃矿区为研究对象,设置不同恢复实验,监测恢复样地内的土壤与植被变化。结果表明:(1)采金活动后,严重破坏了当地的自然景观,形成了一个与周围环境极不协调的外观;(2)从植被恢复的角度,采取恢复措施后,地上生物量的恢复效果显著,较废弃矿区提高了223.2倍,覆土和人工补种措施恢复效果好;(3)从土壤含量(土石比)的角度,土石比值较废弃矿区最高提高了21.5倍,覆土和河水漫溢措施恢复效果好;(4)各恢复措施样方内土石比与地上生物量两者关系满足线性方程y=413.24x-36.76(R2=0.8905,P0.05),即地上生物量随着土石比的增大而增加;(5)初步推算出采取覆土措施后,土壤含量(土石比)和地上生物量恢复到原始草地水平的理论年限分别是7.3年、8.4年。     

三江源区草地荒漠化对局地气候影响的数值模拟

利用美国NCAR中尺度非静力平衡模式MM5V36模拟分析了三江源区草地荒漠化对局地气候的影响。模拟结果表明:草地荒漠化后,源区地表温度白天升高晚上降低,昼夜温差增大;空气湿度减小;感热通量增加,潜热通量减小;边界层高度白天增加晚上减小,昼夜差增大,边界层内能量损失增加。综合分析说明草地荒漠化后源区气候变的更加干燥,不利于植被生长和水土保持,环境变的更加恶劣。