覆盖对果园土壤真菌数量年变化的影响

试验结果表明，在整个果树生长期内，覆盖可明显增加各土层中真菌的数量，０ ～２０ｃｍ 土层中，年平均真菌数量增加７９ ．３９％ ，２０ ～４０ｃｍ 土层中增加２８ ．２４ ％ ，４０ ～６０ｃｍ 土层中增加８５ ．０５ ％ 。无论覆盖与对照，不同土层真菌数量年变化均呈单峰曲线变化，高峰出现在８ 月份。     

钻孔灌注桩施工中岩层漏浆故障处理

本文通过对某大桥钻孔灌注桩施工情况分析。阐述了钻孔灌注桩施工中岩层漏浆故障的原因。同时介绍了几种处理方法。如补浆法、封堵法、内护筒法。     

关于单层刨花板热压机设计中的几个要点

本文论述了热压机在刨花板生产过程中的重要地位 ,分析了单层热压机的优缺点 ,从热压机框架结构、液压系统、热压板、油缸分布等几方面进行了详尽的论述 ,并分析了设计要点。     

Tree identity surpasses tree diversity in affecting the community structure of oribatid mites (Oribatida) of deciduous temperate forests

The role of tree diversity and identity as determinants of soil animal community structure is little understood. In a mature deciduous forest dominated by beech we identified clusters of one, two and three tree species of beech, ash and lime allowing to investigate the role of tree species diversity and identity on the density and community structure of oribatid mites. To relate oribatid mite community structure to environmental factors we measured leaf litter input, fine root biomass, mass of organic layers, topsoil pH and C and N content. We expected oribatid mite density to increase with increasing tree diversity, but we expected the effects of tree species identity to override effects of tree diversity. Further, we hypothesized the density of oribatid mites to be reduced by the presence of beech but increased by the presence of lime and ash. As expected tree diversity little affected oribatid mite communities, whereas tree species identity strongly altered density and community structure of oribatid mites. However, in contrast to our expectations the density of oribatid mites was highest in presence of beech indicating that many oribatid mite species benefit from the presence of recalcitrant litter forming thick organic layers. Especially Oppioidea benefited from the presence of beech presumably due to an increased availability of food resources such as fungi and nematodes. Lower density of oribatid mites in monospecific clusters of lime and ash suggests that oribatid mites did not benefit from high quality litter of these species. Notably, large and strongly sclerotized oribatid mite species, such as Steganacarus magnus and Chamobates voigtsi, benefited from the presence of ash and lime. Presumably, these large species better resist harsh microclimatic conditions in shallow organic layers.     

依普黄酮对骨质疏松症笼养蛋鸡OPG和RANKL表达的影响

选用200只24周龄健康海兰褐蛋鸡,随机分为4组:对照组(基础日粮中含钙3.55％)、低钙组(日粮合钙1.27％)、试验Ⅰ组(依普黄酮8 mg/kg,低钙日粮)和试验Ⅱ组(依普黄酮20 mg/kg,低钙日粮),观察依普黄酮对骨质疏松症笼养蛋鸡血清及骨骼骨保护素(Osteo protegerin,OPG)/核因子-相受体活化因子配体(Receptor activatorof NF-κB ligand,RANKL)表达的影响.结果显示:与低钙组相比,30 d时,试验Ⅰ组和Ⅱ组血清OPG分别显著升高33.12％和60.19％(P＜0.05)；60 d时,试验Ⅰ组和Ⅱ组血清OPG分别显著升高35.89％和61.59％ (P＜0.05)；30 d时,试验Ⅰ组和Ⅱ组血清RANKL分别极显著降低63.85％和70.87％(P＜0.01)；60 d时,试验Ⅰ组和Ⅱ组血清RANKL分别极显著降低69.98％和72.85％ (P＜0.01).与低钙组相比,试验Ⅰ组和Ⅱ组骨组织OPG平均光密度分别显著(P＜0.05)和极显著(P＜0.01)升高,试验Ⅰ组和Ⅱ组蛋鸡骨组织RANKL平均光密度极显著低于低钙组蛋鸡(P＜o.01).试验Ⅰ组和Ⅱ组OPG/RANKL值高于低钙组.结果表明,低钙日粮中添加依普黄酮对蛋鸡骨质疏松症可起到一定改善作用,这可能与OPG上调,RANKL下调,影响RANKL信号通路,使其骨量增加,骨结构改善密切相关.     

Relation of Seed Structures to Soybean Cultivar Difference in Pre-germination Flooding Tolerance

Abstract

Flooding during germination inhibits the sprouting and emergence of soybean [Glycine max (L.) Merr.], reducing subsequent growth and yield. Previous studies revealed that cultivars tolerant to pre-germination flooding have a mechanism of reducing water absorption speed (WAS) during the initial stage of inundation; however, seed structures involved in WAS have not been fully clarified to date. The objectives of this study were to identify possible seed structures responsible for cultivar difference in WAS and pre-germination flooding tolerance. WAS of two tolerant cultivars (Peking and Williams) and two susceptible cultivars (Nakasennari and Enrei), which were identified in our previous study, was compared in relation to seed structures. In Peking, WAS was markedly lower than that of the other cultivars, either in intact seed or seed with the seed coat removed, suggesting that both the seed coat and the embryo have a mechanism of reducing WAS in this cultivar. WAS of the hilum side tended to be higher than that of the back side, and sealing of the micropyle significantly lowered WAS, showing that the micropyle rather than the hilum appeared to be responsible for the higher WAS of the hilum side regardless of cultivar. A comparison of cross section area of the hilum revealed that the tolerant cultivars tended to have a larger area than the susceptible cultivars, suggesting that an inner space of the hilum can act as a reservoir at the initial stage of inundation, thereby reducing WAS in tolerant cultivars.     

极端干旱区大气边界层厚度时间演变及其与地表能量平衡的关系

主要采用ECMWF的地表和大气产品分析了中国西北极端干旱区大气边界层厚度与地表能量通量的时间变化特征,同时,结合探空加强观测分析了大气边界层演变的可能因素.得出:西北极端干旱区大气边界层厚度呈现出季节性的年际和年代际变化,夏季大气边界层厚度呈下降趋势,春、秋季节呈现出先增加后降低的趋势,冬季以阶段性降低趋势为主,20世纪80年代是大气边界层厚度的转折时期；感热通量是极端干旱区大气边界层发展的主要热力因素；由于夏季净辐射量、地气温差、粗糙度以及风速等因子随时间演变而呈降低趋势,潜热通量呈增加趋势,导致了边界层高度形成的热力作用减弱,边界层厚度降低；同时,粗糙度和风速也是大气边界层发展的主要动力因素,由于边界层粗糙度和风速降低,促使垂直风切变减小,湍流动力作用减弱,也会导致边界层厚度降低.     

日粮添加蚂蚁粉对鸡蛋品质影响的研究

试验选用360只55周龄农大3号矮小蛋鸡,随机分为4组,每组3个重复,每个重复30只,三层阶梯式笼养.对照组饲喂基础日粮,试验组分别添加1%、2%、3%的蚂蚁粉.预饲期5 d,正饲期28 d,试验结束时进行蛋品质测定以及品尝试验,研究蚂蚁粉对蛋品质以及品尝者感官评价的影响.结果表明:蛋品质试验中,3%试验组比对照组蛋黄色泽高7.08%(P＜0.01),蛋白高度高15.09%(P＜0.05),添加蚂蚁粉对蛋重、蛋黄重以及蛋黄比没有明显影响(P＞0.05),而蛋壳厚度、蛋壳强度、蛋壳重、料蛋比以及产蛋率也无明显变化.品尝试验中,品尝者对鸡蛋气味、蛋黄色泽和口感进行评价,认为4组间气味和口感无显著差异,虽然在蛋黄色泽上,1%试验组与对照组差异最大,但2%试验组的蛋黄色泽却更受品尝者欢迎.     

我国蛋鸡养殖成本收益及其影响因素分析

本文采用多元线性回归方法对2006～2008年中国小规模、中规模、大规模蛋鸡养殖者的成本收益进行了实证分析.研究发现:精饲料价格是影响蛋鸡养殖成本收益的关键,提高鸡蛋价格也是促进蛋农增收的重要因素,鸡蛋产量的稳定增长对蛋鸡成本收益的提高作用很大.