滇池高等沉水植物50年变迁状况对生态修复的启示

跟踪滇池50年来高等沉水植物的演变状况,不但可以更为客观和综合地评判滇池水生态状况及其变化动向,还可以为沉水植物的修复提供科学依据。研究表明,1957—2010年间,滇池共出现高等沉水植物22种,其中1957—1963年19种,1975—1977年11种,1981—1983年13种,1995—1997年和2001年均10种,2008年8种,2010年7种,总体呈现出明显的减少趋势。根据各时段出现的频率,确定穗状狐尾藻(Myriophyllum spicatum)、马来眼子菜(Potamogeton malaianus)和篦齿眼子菜(Potamogeton pectinatus)3种沉水植物可作为滇池生态修复先锋物种;黑藻(Hydrilla verticillata)、菹草(Potamogeton crispus)、苦草(Vanllisneria natans)和金鱼藻(Ceratophyllum demersum)4种植物可作为较早恢复和种植的对象。微齿眼子菜(Potamogeton maackianus)、穿叶眼子菜(Potamogeton perfoliatus)和大茨藻(Najas marina)可在滇池沉水植物生态恢复中期工程中使用。     

Ecosystem Management Along Ephemeral Rivers: Trading Off Socio‐Economic Water Supply and Vegetation Conservation under Flood Regime Uncertainty

In ecosystems driven by water availability, plant community dynamics depend on complex interactions between vegetation, hydrology, and human water resources use. Along ephemeral rivers—where water availability is erratic—vegetation and people are particularly vulnerable to changes in each other's water use. Sensible management requires that water supply be maintained for people, while preserving ecosystem health. Meeting such requirements is challenging because of the unpredictable water availability. We applied information gap decision theory to an ecohydrological system model of the Kuiseb River environment in Namibia. Our aim was to identify the robustness of ecosystem and water management strategies to uncertainties in future flood regimes along ephemeral rivers. We evaluated the trade‐offs between alternative performance criteria and their robustness to uncertainty to account for both (i) human demands for water supply and (ii) reducing the risk of species extinction caused by water mining. Increasing uncertainty of flood regime parameters reduced the performance under both objectives. Remarkably, the ecological objective (species coexistence) was more sensitive to uncertainty than the water supply objective. However, within each objective, the relative performance of different management strategies was insensitive to uncertainty. The ‘best’ management strategy was one that is tuned to the competitive species interactions in the Kuiseb environment. It regulates the biomass of the strongest competitor and, thus, at the same time decreases transpiration, thereby increasing groundwater storage and reducing pressure on less dominant species. This robust mutually acceptable strategy enables species persistence without markedly reducing the water supply for humans. This study emphasises the utility of ecohydrological models for resource management of water‐controlled ecosystems. Although trade‐offs were identified between alternative performance criteria and their robustness to uncertain future flood regimes, management strategies were identified that help to secure an ecologically sustainable water supply. Copyright © 2014 John Wiley & Sons, Ltd.     

Fish Assemblage Structure and Habitat Associations in a Large Western River System

Longitudinal gradients of fish assemblage and habitat structure were investigated in the Kootenai River of northern Idaho. A total of 43 500‐m river reaches was sampled repeatedly with several techniques (boat‐mounted electrofishing, hoop nets and benthic trawls) in the summers of 2012 and 2013. Differences in habitat and fish assemblage structure were apparent along the longitudinal gradient of the Kootenai River. Habitat characteristics (e.g. depth, substrate composition and water velocity) were related to fish assemblage structure in three different geomorphic river sections. Upper river sections were characterized by native salmonids (e.g. mountain whitefish Prosopium williamsoni), whereas native cyprinids (peamouth Mylocheilus caurinus, northern pikeminnow Ptychocheilus oregonensis) and non‐native fishes (pumpkinseed Lepomis gibbosus, yellow perch Perca flavescens) were common in the downstream section. Overall, a general pattern of species addition from upstream to downstream sections was discovered and is likely related to increased habitat complexity and additions of non‐native species in downstream sections. Assemblage structure of the upper sections were similar, but were both dissimilar to the lower section of the Kootenai River. Species‐specific hurdle regressions indicated the relationships among habitat characteristics and the predicted probability of occurrence and relative abundance varied by species. Understanding fish assemblage structure in relation to habitat could improve conservation efforts of rare fishes and improve management of coldwater river systems. Copyright © 2015 John Wiley & Sons, Ltd.     

Impact of Incision of Gravel‐bed Rivers on Ground Beetle Assemblages

The impact of river incision induced by channelization and gravel mining on the structure of ground beetle assemblages in riparian habitats was investigated on three montane rivers in southern Poland. Ground beetles were collected on three benches of different elevation in 11 incised and 14 vertically stable cross sections of the rivers. In total, 5821 individuals representing 106 species were collected. The effect of river incision on the diversity and abundance of ground beetles depended on bench height. Only on the lowest bench, inundated about once per year on average, species richness of the assemblages was significantly reduced in incised river cross sections. On this bench, the abundance of the specialists of exposed riverine sediments, i.e. small and medium‐sized predators with high dispersal power and spring breeding strategy, was highly negatively affected by river incision. On the highest bench, large, brachypterous species with spring and autumn breeding strategy, typical of undisturbed habitats, were more abundant in incised cross sections. As this bench is practically not subjected to flooding even in vertically stable cross sections, these species probably benefited from the occurrence of riparian forest along most incised river sections, whereas the riparian areas along vertically stable sections are subjected to higher agricultural pressure. This study shows that in the mountain region where high precipitation helps to maintain moisture of the riparian habitats, river incision has a negative impact only on the specialists of exposed riverine sediments. Copyright © 2016 John Wiley & Sons, Ltd.     

Etching of n-type silicon in (HF+oxidant) solutions: in situ characterisation of surface chemistry

The etching of n-type silicon in hydrofluoric acid solutions containing active oxidising agents has been studied. The effect of different parameters on the etch rate of silicon in these solutions has been examined. Based on electrochemical experiments coupled to in situ real-time measurements by infrared spectroscopy, the evolution of surface chemistry during etching of Si has been investigated. It has been found that dissolution of silicon may take place with and without oxide formation on the electrode surface, depending on the composition of etching solution. The transition between conditions giving rise to porous silicon generation and those leading to surface polishing was analysed, when the concentration of oxidising species is increased. In the polishing regime, oxide thickness was estimated from the intensity of the SiO absorption band.     

NJφ1 200mm绝热冷激式内件在联醇塔中的应用

介绍了NJφ1200mm复合冷激型联醇塔内件的设计思路、工艺及催化剂的装填情况。使用结果表明。此塔换热列管少.结构合理。自热效果好;催化剂筐有效容积大,装填均匀密实,催化剂还原彻底,利用率高。     

发动机悬置软垫的有限元分析

以动力总成后悬置软垫为研究对象．探讨了橡胶隔振器弹性特性的有限元分析方法。文中介绍了有限元分析的基本理论。论述了橡胶超弹性特性本构关系的建立。对轿车发动机悬置橡胶软垫在三个垂直方向的力／位移特性进行了有限元分析，并和试验结果进行了对比，有现实的生产指导意义。     

综合采煤机械化设备用系列橡胶密封件

介绍了综合采煤机械化设备用系列橡胶密封件胶料的配合与加工技术，研制的产品性能符合标准要求，已应用于工业生产。     

Chromatographic analysis of species specific odor profiles inMastomys natalensis andM. coucha (Rodentia: Muridae)

Whole-body volatiles from males of the cryptic multimammate mouse speciesMastomys natalensis andM. coucha were analyzed by dynamic solvent effect sampling and capillary gas chromatography. One compound, 3-nonene-2-one, was always present, sometimes as the major component, in volatiles fromM. coucha and absent, or present only at low levels, in volatiles fromM. natalensis. The mean ±SD of the 3-nonen-2-one peak area forM. coucha was 8599 ±9630 and forM. natalensis 148 ±486. Chromatographic analysis was more reliable in identifying a male's species than were a female's in a two-choice olfactorium.