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101.
基于野外采样、定点观测和室内实验,研究青海湟水河流域不同退耕还林模式水文效应,结果表明:不同林分类型枯落物有效持水性大小顺序为云杉桦树混交〉桦树〉云杉〉沙棘,其林下土壤持水性大小顺序为云杉桦树混交〉沙棘〉桦树〉云杉〉农田;森林土壤是森林生态系统水文效应的主体,枯落物和土壤总持水性大小顺序为云杉桦树混交〉沙棘〉桦树〉云杉〉农田。不同林分类型枯落物持水量决定于枯落物蓄积量和自然含水率,其林下土壤持水量决定于土壤非毛细管孔隙度。  相似文献   
102.
梁冠威 《广东园林》2012,34(4):11-14
生态护岸是结合植物与土木工程对河道坡面进行防护的一种新形式。生态护岸集防洪效应、生态效应、景观效应和自净效应于一体,是生态文明时代河道护岸技术的发展方向。文章概述了目前国内生态河道护坡构建技术的发展现状,并对KEYSTONE生态河道护坡砖在广州东濠涌综合整治工程中的应用进行了探讨研究。  相似文献   
103.
Giant river prawn (Macrobrachium rosenbergii) farming plays an important role in the economy of Bangladesh. Presently, it is cultured in around 50 000 ha area with total annual production of 23 240 t. Traditional extensive prawn farming has been expanding over the last three decades through the introduction and adoption of improved culture systems, such as culture of prawn‐carps, prawn‐shrimp‐fish and prawn‐fish‐rice as concurrent and rotational systems. Efforts for the development of improved techniques on broodstock management, seed production and rearing and grow‐out of prawn have been made over the last decade. The outcomes are low‐cost feed for broodstock, production of post‐larvae in net cages (hapa), all‐male prawn culture, periphyton based prawn‐tilapia culture, C/N based prawn culture, organic prawn farming, prawn‐mola culture and prawn‐carp‐mola polyculture. Despite the development of culture technologies, a number of challenges for sustainable development of prawn farming need to be overcome to realize the potentials of this promising sector. Good aquaculture practises at all levels and application of measures for quality control and food safety would ensure sustainable development of prawn farming in Bangladesh.  相似文献   
104.
澧水常德段水环境质量现状分析与评价   总被引:1,自引:0,他引:1  
比照《地表水环境质量标准》(GB3838—2002),运用综合评价指数法,对2007年度澧水常德段石门县三江口、津市市窑坡渡、安乡县沙河口3个监测断面的水质现状进行分析与评价。结果表明:澧水常德段水质总体上达到地表水Ⅲ类标准,水质良好,其中石门县三江口和安乡县沙河口所有监测项目均处于标准值范围,津市市窑坡渡存在粪大肠菌群超标现象。今后应加强水环境监测能力建设,重视水资源合理开发利用,统筹安排生产、生活用水,严格控制排污量,为地方经济社会发展提供可持续的水利保障。  相似文献   
105.
Abstract Weekly exploitation rates of Atlantic salmon, Salmo salar L., in the River Utsjoki, Finland, were estimated from catch reports during the 2003, 2004, 2006 and 2007 seasons, and recordings of all Atlantic salmon ascending the river using a submerged video camera array. In all years, mean weekly fishing mortality rates were significantly higher in June than July to August, with a falling trend throughout the fishing season. Owing to overlap in size between one‐sea‐winter (1SW) and multi‐sea‐winter (MSW) salmon, the estimated fishing mortality rates were based on all sea‐age categories combined. By the second week in June, 18.3–34.7% of large salmon (only MSW) had ascended, compared with 2.2–6.4% of small salmon (1SW and some MSW). Indirectly, the earlier start of ascent of large salmon to River Utsjoki indicated that in‐river fishing mortality of MSW salmon is higher than for 1SW salmon. A later opening of the fishing season may be used to reduce the in‐river fishing mortality, especially for the MSW component.  相似文献   
106.
河西内陆河流域生态问题及其保护对策   总被引:3,自引:0,他引:3  
杨建红  刘建泉 《现代农业科技》2010,(10):298-300,303
概述了近代河西内陆河流域生态研究成果、流域构成特点和河西地区环境状况,分析了河西内陆河流域存在的生态问题,并从节水农业和水权制度改革、城镇化建设、植被保护、生态用水管理、环境污染的治理等5个方面提出了生态保护对策。  相似文献   
107.
Abstract – The morphologies of sympatric juvenile Atlantic salmon Salmo salar parr and brown trout Salmo trutta parr were compared between Irish rivers with contrasting hydraulic environments – a high‐gradient and a low‐gradient tributary from the River Barrow catchment, south‐east Ireland and a high‐gradient river from the Burrishoole catchment, west of Ireland. The two catchments differ markedly in mean annual precipitation (849.0 mm year?1 and 1370.3 mm year?1 for the Barrow and Burrishoole catchments, respectively). Parr of both species demonstrated morphological variation between and within catchments. Changes in metrics such as pectoral fin length, body depth and body length between and within catchments suggest that hydraulic forces were a major determinant of morphological variation. Both species from the Burrishoole catchment had relatively larger pectoral fins, longer heads, larger eyes and shallower bodies than conspecifics from the Barrow catchment. In rivers subject to frequent rainfall‐driven high discharges, such as those in the Burrishoole catchment, a more fusiform body and head shape coupled with larger pectoral fins may reduce the energetic cost of maintaining position in the water column, as well as increase stability and manoeuvrability. The larger eyes in both parr species in the Burrishoole catchment could further be a response to the lower visibility of the more turbid and peat‐stained waters or to the reduced prey availability. The results of this study demonstrate that local adaptation to flow conditions can yield morphologically distinct populations and that multiple species can exhibit parallel phenotypic responses to changing environmental conditions.  相似文献   
108.
成都市府南河工程草坪建植与管理的研究   总被引:5,自引:1,他引:4  
白史且  张友金 《四川草原》1999,(1):20-22,27
成都市府南河改造工程是以环保绿化为中心的全面市政改造工程,绿地以草坪为主。根据成都的自然条件和对草坪的质量要求,选择改良的高羊茅(FestucaarundinaceaSchreb.)为建群种,草地早熟禾(PoapratensisL.)为伴生种,混播建植。注重修剪、除杂、防病虫、施肥等日常管理,并提出了加强管理的几点建议。  相似文献   
109.
长江具备丰富的水资源和电力资源,近年来河网闸坝、水电等水利设施被大量建设,导致了连通性下降,从而带来一系列的生态环境问题,评估长江流域河-库连通性具有重要意义。本研究选择长江流域高坝大库(金沙江下游)、低坝枢纽(汉江中下游)和山区小水电(景谷)三种河-库连通类型进行研究。首先概化典型研究区河-库连通的水文网络模型,并将水电站、过渡区、河流汇聚点、闸坝作为重要的网络节点。然后基于网络的水文连通功能、生态环境功能和社会贡献功能构建水文网络连通评估指标体系,利用熵权模糊综合评估方法对典型河-库进行分析。结果表明,高坝大库和低坝枢纽连通性为四级(差),山区小水电连通性为五级(极差)。并基于评估结果,对不同类型的河-库系统给出改善连通性的针对性建议。  相似文献   
110.
Abstract – Factors associated with the spatial and temporal variation of the lower Guadiana basin (southern Iberia) fish community were determined using data from 20 sites sampled during the summer of 1994 (dry year following a period of low discharge, total discharge from 1992 to 1994=1.45×109 m3) and again during the summer of 1996 (wet year following a period of higher discharge, total discharge from January 1995 to August 1996=6.18×109 m3). From the 17 explanatory variables initially considered six were retained for analysis by a forward selection procedure: maximum depth, altitude, channel width, substrate coarseness, SALT (a dummy variable identifying sampling locations belonging to tributaries that discharge to the brackish Guadiana) and YEAR (a dummy variable identifying the sampling year). Further, we partitioned the total variability in the Guadiana fish community into that accounted uniquely by selected environmental variables (34.9%), uniquely by sampling year (4.1%), by both sampling year and environmental variables (0.3%), and unexplained (60.7%). NOTE  相似文献   
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