Effects of Population Density on the Vegetative Growth of Leafy Reduced-stature Maize in Short-season Areas     

S. H. Begna  R. I. Hamilton  L. M. Dwyer  D. W. Stewart  D. L. Smith 《Journal of Agronomy and Crop Science》1999,182(1):49-55

Maize hybrids which produce more leaves above the ear, with leaf area indices similar to conventional hybrids, which require fewer corn heat units to flowering and maturity, and tolerate higher population densities, should be better adapted for production in short season areas than currently available hybrids. Leafy reduced-stature maize hybrids, which have only recently been developed, have traits which address these criteria. The objective of this study was to evaluate the effects of different population densities (50 000, 100 000, 150 000, and 200 000 plants.ha⁻¹) on the vegetative growth of one leafy reduced-stature (LRS), one non-leafy reduced-stature (NLRS), and two conventional control hybrids (Pioneer 3979, < 2500 CHU, and Pioneer 3902, 2600–2700 CHU) at two locations. There were no differences among population densities for leaf number above the ear; however leaf area index increased as population density increased for all hybrids. The LRS hybrid had a greater average leaf number above the ear (2.7 and 2.0 more leaves than NLRS and the control hybrids, respectively). As a result the leaf area index value of LRS was much greater than the NLRS and similar to the conventional hybrids, but LRS matured substantially before the conventional hybrids. The LRS hybrid required fewer corn heat units to reach flowering and maturity and had more time for grain filling than the conventional hybrids. Therefore, LRS hybrids show promise for production in short season areas where maize cultivation is not economical due to shortness of growing season.  相似文献   

Benefits of repeated stocking with adult,hatchery‐reared brown trout,Salmo trutta,to recreational fisheries?   总被引：1，自引：1，他引：0  

J. BAER  K. BLASEL  & M. DIEKMANN 《Fisheries Management and Ecology》2007,14(1):51-59

Abstract  Recaptures of adult, hatchery-reared, brown trout, Salmo trutta L., and fishing time from anglers were used to evaluate the benefits of stocking programmes with repeated releases of adult brown trout. The recapture rate varied between 17% and 29%. The time between stocking and capture (referred to as residence time) varied between 1 and 160 days (median 3–49 days). Between 67% and 84% of trout caught in the river were recently released fish. Fishing effort increased after stocking, thereby increasing the impact of angling on wild stocks. Stocking with adult brown trout decreases the impact of angling on wild trout only if the time spent fishing by all anglers is kept stable. Furthermore, because of the short residence time of stocked trout, long-term impacts through competition for space and food, or genetic impact through introgression, are limited.  相似文献   

简易原木装车装置     

方世杰  宁宁 《森林工程》1997,13(3):44-46

原木生产和运输所占比例愈来愈大、已达30～50%、但森林资源分散、装车点原木量不大.设置专门装车机械设备不经济.必需由人力使用简易原木装车装置进行装车.文中提出原木装车要求.分析了简易原木装车装置的类型及特点,并确定装车生产率计算公式.  相似文献   

试论森林可持续经营单元的时空尺度   总被引：5，自引：1，他引：5  

谢剑斌  查轩 《林业科学》2005,41(3):164-170

尺度选择是科学研究的重要环节。本文评析传统森林经营单元的时空尺度选择特征及其局限性,指出为了实现森林可持续经营与发展,应该引进新的尺度观念,扩展森林经营单元的基本时空尺度。在简析景观管理与一般可持续发展研究关系基础上,从镶嵌体稳定和动态整体优化、对生物多样性保护工作的融合、生态服务功能表现的尺度依赖特征、采伐等行业实践的景观尺度影响、与其他景观尺度土地可持续管理工作的协调等角度重点论证景观尺度对于设计、管理以及度量森林可持续经营的独特价值;同时提出并初步讨论流域生态区、生态周期以及与景观相对应的世代尺度等时间尺度在森林可持续经营与发展中的应用。  相似文献   

基于宗地代码的不动产统一代码编制规则研究   总被引：1，自引：0，他引：1  

张鸿儒  胡志超 《林业调查规划》2015,40(1):15-18

《不动产登记暂行条例》的出台,标志着不动产登记将进入全新的阶段,不动产登记数据库也将进入全面整合阶段。文章对不动产数据库建设的其中一个技术关键点—登记单元的编码规则进行研究探讨,通过对比分析现行土地、房屋、林地登记中登记单元的特点及编码方式,结合不动产统一登记中登记单元的特点,整合各部门编码规则,提出了适用于不动产登记的统一代码编制规则建议方案,客观总结方案存在的局限性,为后续研究及应用提供参考。  相似文献   

国产电驱离心压缩机组在天然气管道的应用     

刘建臣  刘攀 《油气储运》2021,(2):131-137,165

近年来,电驱离心压缩机组在天然气管道压气站中被大量采用,国产电驱机组虽然起步较晚,但发展较快。回顾了国产电驱离心压缩机组在天然气管道的应用现状及发展概况,系统归纳了机组主要单元的组合方式、成套方式、电动机、变频调速装置、控制系统的主要技术特点。通过运行数据分析、典型故障分析及与进口机组对比分析等方法,归纳总结了国产电驱机组相对进口压缩机组的优势与不足,并在设计、运行、管理及售后方面提出建议。从20 MW以上国产电驱机组研制、国产电驱机组推广、变频高速异步电动机应用、集成式压缩机的研制以及磁浮轴承在国产分体式电驱机组上的研制与应用等方面进行了展望,认为国产电驱机组必将成为未来中国天然气管道输送的核心动力装备,也更加安全、环保、可靠、经济。  相似文献   

玉米收获机低损变径脱粒滚筒设计与试验   总被引：1，自引：0，他引：1  

王镇东  崔涛  张东兴  杨丽  和贤桃  张泽鹏 《农业机械学报》2021,52(8):98-105

针对华北地区玉米收获时籽粒含水率较高、籽粒直收破碎率较高的问题,设计了一种变径脱粒滚筒。滚筒前端直径渐变增大直至与脱粒分离段等径,通过提高滚筒变径段果穗容纳能力,增强果穗之间柔性接触,有效“松散”籽粒之间及籽粒-芯轴之间作用力,使果穗更易于脱粒,从而实现籽粒与芯轴的快速分离,有效提高了脱粒速度,降低了籽粒破碎率。对果穗与脱粒元件受力进行分析,研究变径段锥度对果穗受力的影响。基于动力学仿真试验,分析了果穗与脱粒元件之间的接触力以及果穗-果穗和果穗-脱粒装置之间的接触频次,结果表明,变径滚筒提高了果穗之间的接触频次,降低了脱粒元件与果穗的直接接触,即变径滚筒中果穗之间接触揉搓作用更强。以滚筒转速、凹板间隙及籽粒含水率为试验因素进行了三因素四水平正交试验,确定最优组合为籽粒含水率26%、滚筒转速350 r/min、凹板间隙50 mm,此时籽粒破碎率为4.13%、籽粒未脱净率为0.34%。在籽粒含水率为27%时与等径滚筒进行了对比脱粒试验,按籽粒的完整性将破损籽粒分为全碎籽粒、裂纹籽粒、破皮籽粒及顶部破碎籽粒,结果表明,变径滚筒的籽粒总破碎率为4.64%,比等径滚筒的总破碎率降低19.16%,破损籽粒中全碎籽粒、裂纹籽粒及破碎籽粒所占比例均明显降低;变径滚筒未脱净率为0.42%,比等径滚筒的未脱净率降低51.72%,证明变径滚筒能够有效降低籽粒破碎率及未脱净率。  相似文献   

莱州湾落网开发试验   总被引：1，自引：0，他引：1  

王克洪  温彩玲 《齐鲁渔业》1994,11(1):36-38

莱州湾落网根据莱州湾水浅，流小特点设计而成，通过放大网目，在增端增设导鱼装置，改进固定装置，使网具结构更合理而有创新，９１年专家鉴定认为，本研究成果填补了莱州湾落网作业空白，达到省内先进水平。  相似文献   

上海奉贤区定置张网渔船产值变动分析   总被引：3，自引：0，他引：3  

王淼  洪波  张玉平  孙振中 《上海海洋大学学报》2014,23(2):313-319

为研究上海奉贤区渔民收入水平及变化,利用曲线回归、聚类分析等方法对2009年5月-2012年10月奉贤区定置张网渔船年产值及单位投网数产值(VPUE)等监测数据进行分析。结果显示:渔船产值逐年升高,2009年产值为20.57万元,2012年提高到31.35万元,增幅达到52.4%;VPUE呈现逐年增高之势,2009年为44.59元/网,2012年提升到61.98元/网,增幅接近40%。利用曲线回归估计法对产量与VPUE的相关性进行分析,发现两者无显著相关性(P=0.5010.05),而产值与VPUE具有显著相关性(P=0.0080.05),其关系可以用公式y=33.812lnx+5.3808表达。VPUE季节变化中,春季与夏、秋季均无显著性差异(P=0.0930.05,P=0.1650.05),而夏季与秋季存在显著性差异(P=0.0080.05)。研究表明,渔民不能盲目地以提高总产量为目标来寻求经济效益最大化,而是应该提高渔获物中经济鱼类所占比例和产量,这不仅能够促进渔民增产增收,而且对于保护幼鱼资源,促进渔业资源的合理恢复也具有重要意义。  相似文献   

Filtering method for obtaining stock indices by shark species from species-combined logbook data in tuna longline fisheries     

Hideki Nakano  Shelley Clarke 《Fisheries Science》2006,72(2):322-332

ABSTRACT:   A method of filtering logbook data to obtain estimates of catch per unit effort (CPUE) for sharks has been proposed which simultaneously addresses the issues of under-reporting and the lack of species-specific catch records in historical data. Logbook catch data from vessels with high shark reporting rates are used to represent catch rates for the abundant blue shark Prionace glauca and low reporting vessels' data are used for the main commercially valuable species, the shortfin mako Isurus oxyrinchus . Logbook reporting rate filter (RRF) levels are evaluated through analytical and model-based comparisons to species-specific logbook records available since 1994 and shipboard observer data. At the high reporting rates, the ≥ 80% filter avoids large numbers of false zeros and provides the best fit to observer data for blue shark. At the low reporting rates, the ≤ 40% filter best matches the observer data for makos, but this filter level includes large numbers of false zeros and sharks of other species. The ≤ 20% filter produces a dataset that is better targeted to mako catches but considerably under-estimates CPUE relative to observer records. For these reasons, other means of estimating mako catch rates are suggested for further research.  相似文献