Determination of Effective Degree-Day for Supporting Chemical Control Against Cutworms （Lep. Noctuinae） in the Sugar Beet     

Magdalena Jakubowska  Felicyta Walczak  JerzyJzefatLipa 《农业科学与技术》2012,(3):314-326

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Census and effective population sizes of white‐spotted charr (Salvelinus leucomaenis) in a fragmented landscape          下载免费PDF全文

Shoichiro Yamamoto  Hitoshi Kubota  Koh Hasegawa  Tomoyuki Nakamura 《Ecology of Freshwater Fish》2016,25(4):612-621

Several habitat models have been proposed to predict population size for stream fishes and to guide habitat assessment and monitoring techniques. However, most models do not incorporate the potential advantage of molecular genetic markers. We conducted a field survey and microsatellite DNA analyses to quantify the relationships among genetic diversity, census/effective population size and habitat variables in fragmented populations of white‐spotted charr (Salvelinus leucomaenis). The census population size significantly increased with the stream length, the number of pools and a pool‐riffle sequence index, a proxy for channel‐unit habitat type complexity within reaches. Population density was correlated with the pool‐riffle sequence index only. Genetic diversity and effective population size were not correlated with the habitat variables or census population size. There was a lack of isolation‐by‐distance population structure in the studied populations. Our results suggest that stream length and the number of pools within reaches associated with habitat complexity are the habitat variables that explain the majority of variation in population size of white‐spotted charr. Our findings provide further evidence that census population size per se is a poor indicator of the inclusive genetic diversity within populations in a fragmented landscape.  相似文献   

大中型轴流式潜水电泵开发应用的若干问题探讨     

李志鹏  胡贵敏 《中国农村水利水电》2000,(11):39-41

介绍了大中型轴流潜水泵的基本结构、特点。对该型泵的设计、安装、运行等问题进行了讨论，论述了用该型泵替代目前应用的轴流泵具有的各种优越性。  相似文献   

温度对萝卜蚜生物学特征的影响   总被引：2，自引：1，他引：2  

赵惠燕  汪世泽  张文军  肖文宽 《植物保护学报》1990,17(3):223-227

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Breed risk of pyometra in insured dogs in Sweden   总被引：1，自引：0，他引：1  

Egenvall A  Hagman R  Bonnett BN  Hedhammar A  Olson P  Lagerstedt AS 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》2001,15(6):530-538

An animal insurance database containing data on over 200,000 dogs was used to study the occurrence of pyometra with respect to breed and age during 1995 and 1996 in Swedish bitches <10 years of age. A total of 1,803 females in 1995 and 1,754 females in 1996 had claims submitted because of pyometra. Thirty breeds with at least 800 bitches insured each year were studied using univariate and multivariate methods. The crude 12-month risk of pyometra for females <10 years of age was 2.0% (95% confidence interval = 1.9-2.1%) in 1995 and 1.9% (1.8-2.0%) in 1996. The occurrence of pyometra differed with age, breed, and geographic location. The risk of developing pyometra was increased (identified using multivariate models) in rough Collies, Rottweilers, Cavalier King Charles Spaniels, Golden Retrievers, Bernese Mountain Dogs, and English Cocker Spaniels compared with baseline (all other breeds, including mixed breed dogs). Breeds with a low risk of developing the disease were Drevers, German Shepherd Dogs, Miniature Dachshunds, Dachshunds (normal size), and Swedish Hounds. Survival rates indicate that on average 23-24% of the bitches in the databases will have experienced pyometra by 10 years of age. In the studied breeds, this proportion ranged between 10 and 54%. Pyometra is a clinically relevant problem in intact bitches, and differences related to breed and age should be taken into account in studies of this disease.  相似文献   

柽柳有效天敌昆虫筛选标准的建立   总被引：1，自引：1，他引：1  

孟玲  李保平 《中国生物防治》2005,21(3):192-195

参照前人对杂草天敌筛选标准、植物与昆虫互作理论和近年来对柽柳原产地主要天敌生物学特性的研究结果，制定出柽柳天敌遴选量化标准，共计10项特征，满分为47分。并以此对取食柽柳的12种天敌进行了筛选。柽柳条叶甲得分最高（43分），其次是斯氏伞锥象（41分），推荐这2种天敌昆虫作为首选天敌引入美国做进一步评价。  相似文献   

小麦生产的生态定位及发展策略   总被引：4，自引：1，他引：3  

卫云宗  刘新月  张久刚  张定一 《农业现代化研究》2003,24(5):392-395

本文运用生态学及系统工程学的基本原理,分析了山西省小麦生产发展现状,确立了加入WTO后小麦生产的生态地位,即小麦是自然资源利用效率高、生态效益大的生态型作物。提出了小麦生产可持续发展的策略是：稳定面积,提高单产,改进品质。提高资源利用率。保护和优化生态环境。同时指出小麦生产是社会效益高、生态效益大,而本身经济效益低的弱质产业。应该从社会效益、生态效益和经济效益三者协调发展的角度出发。把小麦生产的巨大生态效益放在突出地位。  相似文献   

奶牛的有机锌应用效果研究进展     

梁建光 《乳业科学与技术》2007,29(6):274-277

就有机锌对奶牛的营养作用效果、影响有机锌作用效果的因素进行综述。认为添加有机锌可提高奶牛的产奶性能、免疫机能、繁殖性能,改善体健康。同时影响有机锌作用效果的因素有:有机锌的产品质量、添加量和添加时期、饲料营养水平、参照物类型和评价指标等。  相似文献   

接种高效根瘤菌对紫花苜蓿—禾本科混播组合生产性能的影响     

曾昭海  胡跃高  陈文新  隋新华  陈丹明 《干旱地区农业研究》2006,24(5):55-58

利用筛选的高效根瘤菌接种紫花苜蓿,分别与高羊茅、无芒雀麦及1年生黑麦草混播。与对照相比,接种高效根瘤菌后,紫花苜蓿-高羊茅混播组合中苜蓿干草增产17.0%,高羊茅增产15.1%,总计增产16.3%;紫花苜蓿-无芒雀麦混播组合中紫花苜蓿增产14.0%,无芒雀麦增产51%,总生物量增产20.5%;紫花苜蓿-1年生黑麦草混播组合中,紫花苜蓿增产7.6%,1年生黑麦草干草产量比对照增产4.8%,总生物量增产6.8%。从LER(Land equivalent ratio)和CR(Competitive ratio)变化看,接种高效根瘤菌有利于提高LER值和禾本科作物的CR值。  相似文献   

甘肃省年有效降水次数的异常特征分析   总被引：4，自引：5，他引：4  

杨金虎  王润元  姚玉璧  吴胜安 《干旱区研究》2006,23(1):109-114

利用1958-2001年甘肃省45个气象站的逐日降水资料,统计出年有效降水次数,通过经验正交展开(EOF)和旋转经验正交展开(REOF),研究其异常的空间结构及时间演变规律,同时利用墨西哥帽子波变换技术,对甘肃省年有效降水次数进行多时间尺度分析.结果表明:大范围区域一致性异常是甘肃省年有效降水次数的首要特征;甘肃省年有效降水次数异常区域大致分为4个关键区;从总体上看(较大时间尺度),甘肃省年有效降水次数是增加的,而从较小时间尺度看,则表现为增中有减,减中有增的复杂变化.  相似文献