黑土长期定位试验原状土搬迁对土壤真菌群落多样性的影响

采用PCR-DGGE及其特异性条带克隆测序的方法,研究黑土长期定位试验原状土整体搬迁对土壤真菌群落结构多样性的影响。对同为小麦茬的搬迁前(2010年)和搬迁后(2013年)土壤真菌群落结构的研究表明:DGGE图谱中搬迁前后2个土层不同处理的样品间条带的数量和亮度存在部分变化;对DGGE图谱进行聚类分析可得,真菌群落结构在2个土层各处理中搬迁前后有部分变化,其中MNPK处理的变化较为显著;对DGGE图谱主成分分析结果可得,在0~20 cm土层中各处理虽然搬迁前和搬迁后产生分异,但搬迁前后的3年中处理间的分布规律相似,在20~40 cm土层中搬迁前和搬迁后MNPK和CK处理的分布规律发生了变化。搬迁前和搬迁后土壤真菌群落结构受到搬迁扰动的影响远小于耕作方式、植被类型、土壤肥力等的影响。     

Use of satellite data to identify critical periods for early life survival of northern shrimp in the Gulf of Maine

The northern shrimp Pandalus borealis is at its southern limit in the Gulf of Maine (GOM), and recruitment success is higher in years with relatively cool water temperature. However, the mechanisms for the temperature effect are not clear. We used rolling window analysis of daily satellite data to identify critical periods for early life survival of the 1998–2012 northern shrimp year‐classes and to investigate the importance of the phenology of the hatch and bloom. Survival was negatively correlated with sea surface temperature (SST) during a 6‐week period around the time of larval emergence (late winter) and during a 4‐week period in late summer when SST and stratification reached annual maxima. Survival was negatively correlated with chlorophyll‐a concentration (chl‐a) during two 5‐week periods centered approximately a month before the hatch midpoint and around the time of settlement to the benthos. A small‐magnitude winter bloom occurred around the time of the hatch in many years, but our results did not reveal a link between survival and bloom‐hatch phenology. The timing of winter and spring blooms were correlated with SST during the preceding 10 months. A survival model including SST and chl‐a during the critical periods explained 73% of the variance in survival. Summer SST increased significantly during the study period; the other critical variables showed no trend. The rolling windows approach revealed sensitive periods in early life history that may not have otherwise been hypothesized, providing a foundation for research towards a greater understanding of processes affecting recruitment.     

珙桐迁地保护现状及技术策略探讨

笔者对珙桐资源的分布状况、国内外引种栽培情况作了较全面的介绍,对珙桐濒危原因、迁地保护的影响因素进行分析,对迁地保护技术和方法进行探讨。     

福建省延平区笋竹加工企业积极应对金融危机

面对蔓延全球的经济危机,从科技发展、营销、节约成本和确保资金运行等方面阐述了福建省延平区笋竹加工企业积极应对当前金融危机所采取的措施。     

枣与冬小麦间作巷道内的光环境特征

为了探明枣与冬小麦间作系统中间作巷道内与冬小麦生长发育需求相适应的光环境变化特征,为枣与冬小麦间作系统的栽培管理提供科学依据,以株行距1.0 m×4.5 m、1.0 m×2.5 m、0.5 m×4.5 m的枣与冬小麦间作系统为研究对象,使用Li-6400XT便携式光合作用测定仪和LAI-2000植物冠层分析仪及配备的LI-191线状量子传感器测定冬小麦不同生育期光合生理参数和间作巷道内的光合有效辐射,通过光合有效辐射时空窗法计算出了不同生育时期冬小麦冠层饱和光合有效辐射时空窗的大小。结果表明：冬小麦不同生育时期的光补偿点(LCP)表现为成熟期＞灌浆期,光饱和点(LSP)表现为灌浆期＞成熟期;不同株行距枣与冬小麦间作系统中,灌浆期和成熟期冬小麦冠层饱和PAR时空窗的大小1.0m×4.5 m＞0.5 m×4.5 m＞1.0 m×2.5 m。从满足间作巷道内的冬小麦光合需求考虑,目前新疆南疆盆地枣与冬小麦间作主要采用的几种株行距中,1.0 m×4.5 m的株行距为最佳的枣与冬小麦间作模式。     

轮面曲率半径对沙地刚性轮沉陷性能影响研究

轮面曲率半径对沙地刚性轮的沉陷性能影响至关重要。通过轮面承压试验、轮壤台架动态试验和离散元数值模拟分别对6种不同轮面曲率半径的平面、凹面和凸面沙地刚性轮在3种不同颗粒形状及粒径大小沙土上的沉陷性能进行分析。在轮面承压试验中,相比其他轮面曲率半径的车轮,平面轮在细径石英砂和粉尘状火山灰上的抗沉陷性能均最好。与其他沙土介质相比,粗径石英砂上所有轮面车轮的沉陷量最小。轮面承压模拟结果表明,平面轮下沙土颗粒的力场分布均匀,轮下颗粒溢出量小,有效说明平面轮沉陷量最小的原理。在细径石英砂轮壤台架动态试验中,凹面R80车轮在行驶初期(位移小于50 cm)沉陷量最小,行驶到稳定状态后(位移大于70 cm),凹面R60车轮的动态沉陷量最小;在粉尘状火山灰轮壤台架动态试验中,凹面R60车轮在整个运动范围内的沉陷量最小。因此,在细径石英砂和粉尘状火山灰上行驶过程中,轮面曲率半径较大的凹面轮的抗沉陷性能较好。此外,由车轮行驶在细径石英砂离散元模拟可知,凹面轮的受力区域集中在轮面两侧,轮面内凹结构可有效防止沙土侧向流动并减小对沙土的扰动。本文研究不仅为承压和行驶条件下不同曲率半径轮面的车轮在沙土介质上的沉陷性能判断提供参考依据,而且为沙漠或者深空探测车辆轮/胎的轮面结构设计提供重要理论依据。     

大型喷灌机变量灌溉技术研究进展

变量灌溉具有借助变量灌水方法、定位方法和控制系统在田块内改变灌水深度,应对特定的土壤、作物和其他条件的能力,是解决大型喷灌机较大单机控制面积内土壤、作物空间变异问题,提高灌溉水利用效率,充分挖掘整个田块作物生产潜力的水分管理方法。由于变量灌溉技术研究起步较晚,中国的研究刚处于起步阶段,尚缺乏成熟的变量灌溉管理理论与技术。该文在系统总结国内外研究成果的基础上,从变量灌溉内涵、大型喷灌机变量灌溉系统构建、变量灌溉管理分区、决策支持系统以及变量灌溉效益5个方面分析了大型喷灌机变量灌溉技术研究进展。结果表明,目前关于大型喷灌机变量灌溉系统组成方法的理论研究相对比较成熟,其主要由变量供水装置、定位系统、控制系统三部分组成,大型喷灌机变量灌溉系统软硬件开发尚存在较大的发展空间。基于作物生长指标的变量灌溉动态处方图、将变量灌溉技术与非充分灌溉原理相结合的水分管理决策方法,以及利用变量灌溉施肥系统进行喷灌水肥一体化研究,代表着集约化农田大型喷灌机水肥精准管理的重要发展方向。该文可为提高大型喷灌机水分管理水平,实现精准灌溉提供参考。     

一种屋脊大开窗玻璃温室开窗机构的设计

全面论述了屋脊大开窗玻璃温室的开窗机构原理及受力分析,提出开窗机构各结构参数与传动系统受力关系,为正确选择减速电机提供依据。     

厨房外挑窗式灶台设计

本文对厨房凸窗式灶台设计从构造、尺度、排烟等方面进行了浅析,其目的充分利用厨房的可 利用空间。     

Effects of short periods of frequent milking on the persistency of milk yield and SCS in Turkish Saanen goats

The major purpose of this study was to investigate if increasing milking frequency for a short period of 3 weeks had any effects on the persistency of milk yield and the persistency of the somatic cell score (SCS). The methyl green–pyronin method was used for the direct microscopic SCS, converted to SCS for the analyses. Two groups were formed (control, n = 14 and treatment, n = 14). The treatment group was milked four times a day for 3 weeks after weaning. Both groups were milked twice a day outside this 3‐week period, throughout lactation. For the milk yield, persistencies were higher in the treatment group when the distance between the test days was equal to or less than 3 months. The exact opposite was true for the SCS; that is, the treatment group had higher persistencies when the distance between the test days was more than 3 months. Overall, persistencies related to milk yield were higher than persistencies related to SCS. For fat corrected milk yield, treatment persistencies were always higher than the control group persistencies, regardless of the distance between the tests. The same was true for the fat content. Increasing milking frequency for a short period of time (3 weeks) after weaning may help to increase the persistency of the milk yield, fat corrected milk yield and fat content. A 3‐D plot of least squares means indicated that the milk yield tended to show a classical lactation curve in lower SCS values while forming an unstable curve in higher SCS values.