河流与开放空间耦合的城市绿地生态网络构建

随着我国城市化进程的加快,城市生态环境面临着越来越严峻的考验,为了促进城市的可持续发展,构建城市绿地生态网络、维护城市生态系统的稳定性成为众多领域研究的重点。河流作为城市绿地生态网络的核心空间结构,开放空间作为绿地生态网络的基础,二者关系的研究对构建城市绿地生态网络具有重要意义。在研究河流与开放空间耦合关系的基础上,结合对城市绿地生态网络含义、功能机制、评价指标的分析,以南阳市为例,提出河流与开放空间耦合的城市绿地生态网络构建方法。     

Extending the Encounter–Norm–Crowding Generalization to Angler Evaluations of Other Social and Resource Indicators

Recreationists who encounter more people than their normative tolerance for seeing others usually feel more crowded than those encountering fewer than their norm. This research note extends this observation–norm–evaluation relationship (e.g., encounter–norm–crowding) to other evaluations and indicators. Data were from a survey of anglers on the Gulkana National Wild River in Alaska (n = 288). Respondents who encountered more people than their norm felt more crowded than those encountering fewer than their norm. When impacts from other social indicators (e.g., camping within sight or sound of other groups, fishing area competition) exceeded user norms, crowding was higher and satisfaction with overall trip quality was lower than for those experiencing less than their norms. When impacts from resource indicators (e.g., litter, impacted campsites) exceeded norms, satisfaction with both environmental quality and trip quality were lower than for those experiencing less than their norms. The encounter–norm– crowding generalization, therefore, extended to other indicators and evaluations.     

Blue sucker stock characteristics in the upper Yazoo River basin, Mississippi, USA

Blue sucker Cycleptus elongatus (L.) in the upper Yazoo River basin, Mississippi, USA was studied using overnight hoop net sets (n = 4093) during 1988 and 1990–1998 to determine the influence of channel dredging. There were 264 blue suckers captured, ranging from 3 to 11 years of age. Length ranged from 265 to 700 mm and weight from 120 to 4700 g. Concurrent studies with smaller mesh hoop nets failed to capture any juvenile blue suckers. Catch‐per‐unit‐effort (CPUE: fish net^?1) declined throughout the study in the Yalobusha River, a river subjected to channel dredging during 1988 and 1994. With the exception of limited hydraulic dredging in the Tallahatchie River, there was no dredging in the other Yazoo River tributaries, nor were there declines in blue sucker catch rates in these rivers. Throughout the upper Yazoo River basin, blue sucker stocks were dominated by adult fish, and there was little evidence of reproduction or recruitment. Conservation of the blue sucker in the upper Yazoo River basin should include actions that ensure the functional integrity of this floodplain river ecosystem and elimination of channel dredging throughout the basin.     

Lethal effects caused by suspended particles and sediment load on zoospores and gametophytes of the brown alga <Emphasis Type="Italic">Eisenia bicyclis</Emphasis>

ABSTRACT:   The effects caused by suspended particles in seawater and sediment cover of the substrate on the attachment to the substrate of zoospores, and on the subsequent growth and survival of gametophytes of the brown alga Eisenia bicyclis were examined in the laboratory. The attachment rate to the substrate of the zoospores was remarkably reduced by the sediment cover on the substrate, and it decreased to 3.8% of the no-sediment control by a slight sediment cover of 3.0 mg/cm² (0.048 mm in thickness). The growth of gametophytes was not inhibited at 10 mg/cm² or less of sediment cover, though it was stopped at 30 mg/cm². The survival rate of gametophytes became 39.4% at 5 mg/cm² on the substrate, and gametophytes were all blighted at 30 mg/cm². The ratio of male to female of the surviving gametophytes became 81.5:18.5, when the sediment cover was 10 mg/cm². The rate of total loss ( TL [%]) of zoospores and gametophytes of Eisenia bicyclis was obtained from the following equation: TL  = 100 (1 − exp[−0.0339  C ] exp[−1.24  Q ]), where, C (mg/L) and Q (mg/cm²) indicate the concentration of suspended particles in seawater and the sediment on the substrate, respectively.     

嫩江中游讷河江段瓦氏雅罗鱼生物学研究

2005年4月对江段瓦氏雅罗鱼2只船渔获物234尾进行渔业生物学研究。捕捞群体平均体长16.6 cm(15～29.5 cm),平均体重151.4 g(50～300 g),年龄由1~ ～5~ 龄组成,2~ 占36%；绝对生殖力为8050～12448粒/g,平均为3700粒/g；相对生殖力9. 04～100.6粒/g,平均为34.3粒/g；肥满度系数雌性为0.9436～2.0547%,平均为1.999%。雄性为1.4577～2.054%,平均为1.6262%。捕捞数量2005年春汛6.75 t。嫩江中游讷河江段瓦氏雅罗鱼资源呈现小型化、低龄化趋势；渔业资源呈下降趋势,亟待采取限定捕捞规格的保护措施。     

绥芬河污染对大麻哈鱼、滩头雅罗鱼及水生生物影响的调查监测

绥芬河为中俄共有河，是黑龙江省的产鱼区之一，本介绍了该河流水质常规分析，工厂污水分析、鱼体残毒分析、浮游动物、浮游植物、底栖生物、着生藻类定性、定量及鱼类急性致毒性试验结果，同时进行了水质评价。结果表明：该河流经环境治理，水质状况得以改善，属于寡污带河流，基本达到渔业水质标准，是我国少有的清洁河流，对该河流洄流的四种大麻哈鱼、两种滩头鱼和生存的其它水生生物不构成危害性影响。     

连江鱼类资源现状调查及资源衰退原因分析

于2005～2006年间对清远市筑坝后连江的鱼类种群结构状况进行了调查。在河流的上游、中游、下游三个江段采样,共采集到鱼类87种,分属于7目18科69属,优势种为亚科(占鲤科总数的29.4%)、鲌亚科(占鲤科总数的15.7%)鱼类。通过与历史资料比较发现,多种适应急流的鱼类、洄游或半洄游性鱼类和产飘浮性卵鱼类已在连江中上游消失,连江鱼类组成、结构和分布已发生了较大的变化。     

虾池沉积物中3类主要细菌的垂直分布特征

采用平板涂布法和MPN法测定了虾池底质下 0到 30cm深度范围内 3类主要细菌类群的垂直分布情况。结果表明 ,底泥中细菌主要集中于 0到 5cm的表层范围内 ,随深度增加 ,数量急剧减少 ,至 30cm深处所测到菌量已很少。底泥中的总菌量随养殖时间推移 ,逐渐增加 ,到养殖中后期 ,表层菌量增加至 10 6CFU/g ,表层以下 10～2 0cm的总异养菌量和硝酸盐还原菌数量也增加至 10 5CFU/ g以上。弧菌仍集中于表层。细菌的垂直分布主要受各层有机物和溶解氧含量的影响     

Assessing the opportunities for upstream migration of non-salmonid fishes in the weir-regulated River Vecht

The degree of obstruction posed by weirs to potential upstream movements of non-salmonid fish (predominantly cyprinids) in the River Vecht, the Netherlands, was assessed. This rain-fed river showed high variability in discharge, providing opportunities for passage at high discharge when weirs were free flowing. Daily recorded discharge and water levels between 1960 and 1984, and an analysis of swimming capacities and migratory behaviour, were used to assess whether hydraulic conditions each day and for each species were suitable for ascent. The assessment demonstrated that migratory opportunities along the six weirs were extremely limited. Only 10 of 32 species were able to ascend all weirs in 5–30% of the years. Opportunities were the greatest for large-sized species during November–March at the downstream-situated weirs, whereas small-sized species had no opportunities year-round. The approach used is widely applicable for barrier assessment in other rivers, because it requires only basic hydraulic measurements that are often available.     

Constructed shallow zones along navigation canals: vegetation establishment and change in relation to environmental characteristics

An Erratum has been published for this article in Aquatic Conservation: Marine and Freshwater Ecosystems 12(2), 2002, 251

• 1. In recent decades shallow zones have been constructed along navigation canals in the Netherlands which form a potential new habitat for aquatic macrophytes and helophytes absent from traditional canals.
• 2. The aim of this study was to examine the relationships between the aquatic plant vegetation that becomes established and the physical and chemical characteristics of water and sediment, in order to find the determinants of species composition and the changes therein. Data were collected in 1998 and 1999 from 80 plots in bank zones at varying stages of development since construction along two navigation canals.
• 3. Plots 3–5 years old were partly dominated by rooting submerged macrophytes such as Potamogeton pectinatus, Elodea nuttallii and Potamogeton pusillus; locally non‐rooting species occurred such as Ceratophyllum demersum, Lemna minor and Spirodela polyrhiza. Older plots contained Phragmites australis, locally mixed with free‐floating species. Hydrological isolation from the eutrophic canals was indicated by the presence of Chara vulgaris.
• 4. Characteristics of both water layer and sediment could explain the variation in vegetation composition. Rooting submerged macrophytes predominantly occurred in sites with a thin (<2 cm) layer of sediment with relatively low concentrations of organic matter; moreover, ammonium concentrations in the water layer and sediment pore water were relatively low. Stands of non‐rooting macrophytes and of Phragmites australis were characterized by a relatively thick sediment layer and high ammonium levels in the pore water. Light limitation in turbid water, associated with navigation and eutrophication, may also play a role.
• 5. Although submerged aquatic macrophytes persist for a relatively short time, shallow zones nevertheless function as a habitat for helophyte communities and contribute to a higher aquatic biodiversity than is associated with traditional banks along navigation canals.

Copyright © 2001 John Wiley & Sons, Ltd.