活鸡价格和饲料价格的短期动态关系和长期均衡

为了了解活鸡价格和饲料价格的短期动态关系和长期均衡关系,在对活鸡价格与饲料价格关系分析的基础上,采集2010 年1 月—2014 年3 月中国活鸡、玉米以及豆粕市场定价的月度数据,利用ARDL-ECM模型对它们的短期动态关系与长期均衡关系展开了评定以及测验。研究结果表明,玉米的市场定价以及豆粕的市场定价对活鸡市场定价均存在一定程度的正向促进作用,并且其能够发挥的长期的影响效应均远远超过短期的影响效应,玉米市场定价对活鸡市场定价的长期以及短期影响效应均极大程度的高于豆粕市场定价对活鸡市场定价的长期和短期影响效应。政府可以通过这一结论,及时做出反应和调整,通过调控和监管,稳定市场的玉米、豆粕、活鸡定价。     

金华城区表层土壤剖面磁化率变化规律

以金华城区表层土壤剖面为研究对象,分析土壤剖面磁化率的分布特点。结果表明:19个土壤剖面的磁化率分布在11.22×10^-8～94.29×10^-8 m³/kg之间;19个剖面土壤磁化率在0—10 cm的垂向剖面上的变化有三种不同形式:一是先增大后减小且在3 cm左右出现极值,二是单调变化,又可细分为单增和单减,三是波动变化,也可细分为波动增加和波动减小;通过对比不同采样间隔下磁化率的变化情况,结合土壤磁化率垂向分布特征和统计结果,建议以1—3 cm作为采样深度可以更好地揭示人类活动对土壤磁化率的影响。     

Some Aspects of Ecology of Chrysichthys nigrodigitatus (Lacepede) in River Niger,Nigeria

A study on the food and feeding habit of Chrysichthys nigrodigitatus(Lacepede) was conducted in River Niger within the region of Oshimili local government area of Delta State Nigeria.A total of 90 specimens were collected with the help of fishermen using gill net,cast net and traps.The fish samples were immediately taken to the laboratory for analysis.Morphometric characteristics such as weight,length,condition factor,egg weight,Gonado Somatic Index(GSI) and sex ratio were determined.The stomach content was analyzed using numerical method to determine the food content.The total length of the fish sampled ranged from 14.40-44.60 cm,while the standard length varied from 11.00 cm to 47.00 cm and the fish body weight ranged between 19.00 g to 503.20 g.Sex ratio 1female to 1 male was observed.The mean condition factor for both male and female obtained was 1.67.Of all the 90 fishes sampled,none had empty gut representing 100%.The major food items were phytoplankton,plant part and Detritus.Out of 41 females sampled,only 17 had eggs and the eggs were matured at stage IV.     

基于EDEM的单粒式谷物水分仪采样机构仿真研究

建立了单粒电阻式谷物水分仪采样机构离散元模型,应用EDEM软件内Hertz-mindlin(no slip)和Hertz-mindlin with bonding两种接触模型对水稻颗粒在水分仪采样机构内的运动及碾压情况进行了仿真,并研究了3种不同的输送辊螺距对采样单粒性的影响,以及碾压辊表面不同的滚花对碾压充分性的影响。仿真结果表明:输送辊螺距越大,其采样效率越低,输送单粒性效果越差。碾压辊表面滚花为p1.2斜纹时碾压较为稳定,充分性最佳。同时,进行了实验验证,结果表明:仿真实验与对比实验结果一致,证明运用离散元法分析采样机构中物料的运动、碾压状态是可行的。     

Small-Scale Spatial Variability of Plant Nutrients and Soil Organic Matter: An Arable Cropping Case Study

Soil properties can vary spatially due to differences in topography, parent material, and land management practices. For site-specific management within the field, information on spatial variation of soil properties is essential. This case study was conducted to quantify the spatial variability of available plant nutrients and organic matter under arable cropping in New Zealand. Within a 10.4-ha paddock that had a long-term history of arable cropping, 91 samples (0–7.5 cm) were collected in a grid pattern for determination of mineral nitrogen (Min N), anaerobically mineralizable N (AMN), Olsen P, total carbon (TC), and total N (TN). The data were evaluated using geostatistical and classical statistical methods. Although the paddock had a flat topography and had been managed uniformly for many years, nutrient concentrations exhibited substantial variability. All measured variables except mineral N showed moderate positional dependence. Autocorrelation distances were 400 m for Olsen P, 293 m for AMN, and 347 m for TC. Soil C showed a strong, positive correlation with the amount of clay plus fine silt (<5 µm fraction) and a negative correlation with sand content. These results suggest that textural variation was a major factor influencing within-field variability in soil organic matter. Using the spatial data, zones with different plant nutrient requirements were identified (four for N; two for P). An application strategy that accounts for fertility differences between zones may improve fertilizer use efficiency and contribute to better environmental outcomes; P inputs could be reduced by 50% by avoiding application to the high Olsen P zone.     

应用PCR-DGGE技术分析福州左海湖的细菌群落组成

应用PCR-DGGE技术对4个月份(2011年12月、2012年2月、4月、6月)的福州左海湖细菌群落组成和优势菌群进行分析,研究结果发现相同月份4个采样点的DGGE图谱差异性不大,细菌群落组成具有较高的相似性;而不同月份4个采样点的DGGE条带的数目和位置表现出明显差异,细菌群落组成差异明显。对20条不同位置的DGGE条带进行切胶回收、扩增和测序后,进行系统进化分析,结果显示这20条带归属于4个细菌类群,即变形菌门Proteobacteria、拟杆菌门Bacteroidetes、放线菌门Actinobacteria、蓝细菌门Cyanobacteria。20条序列中有11条鉴定为变形细菌门Proteobacteria、5条鉴定为拟杆菌门Bacteroidetes、2条鉴定为放线菌门Actinobacteria、其余2条属于蓝细菌门Cyanobacteria。研究结果表明,左海湖细菌群落组成包括了Proteobacteria、Bacteroidetes、Actinobacteria、Cyanobacteria,其中以Proteobacteria为优势菌群。     

Sampling method for estimating neutral allele frequency in a pedigreed population

The estimated allele frequency at neutral DNA marker loci is a fundamental parameter for establishing a conservation scheme for a set of livestock breeds. In this study, we propose a novel 'minimum distance (MD) method' for estimating neutral allele frequencies, which minimizes the error by the use of pedigree information. Using computer simulation and actual microsatellite data for a pedigreed cattle population, the performance of the proposed method was compared with that of conventional random sampling (RND). MD manifests a promising superiority to RND, irrespective of the sample size and the depth of pedigree. It is theoretically demonstrated that the error of the estimates depends on both the sample size and the distance of founder allele frequencies between the sampled and the non-sampled individuals. MD samples individuals so as to minimize the latter source of estimation error.     

一种从马鹿粪便中提取DNA的改进方法(英文)

[目的]介绍一个从马鹿粪便中提取DNA的改进方法。[方法]本实验采用的是,在传统的CTAB裂解法的基础下,根据马鹿粪便的特征摸索出来的改进方法。[结果]采用该方法从天山马鹿粪便中提取了高质量的粪便DNA并扩增了天山马鹿线粒体细胞色素b基因片段,通过测序检测,同时提取马鹿肌肉和皮毛样品的DNA作为对照,进一步证实了提取的可靠性。[结论]该方法提取过程中不需要用蛋白酶K;所提取的DNA不需要用DNA纯化试剂盒纯化,可直接用PCR扩增,因此,费用量很低。     

长期施肥对旱地土壤中氨氧化微生物丰度和分布的影响

采用基于氨单加氧酶基因(amoA)的荧光定量PCR技术,以黄土高原旱地土为材料,研究长期施肥对土壤氨氧化细菌和氨氧化古菌丰度的影响,并分析环境因素与氨氧化菌丰度的关系。以不施肥土壤为对照(CK),设置3个施肥处理,分别为单施磷肥(P),氮、磷共施(NP)和氮、磷、有机肥共施(NPM)3个处理。结果表明,不同处理氨氧化菌amoA基因拷贝数为1.326×106～1.886×106 g-1,各处理间氨氧化细菌丰度差异不显著;氨氧化古菌的arch-amoA基因拷贝数为1.329×106～4.510×106 g-1,表现为处理NPM>NP>CK>P,NPM处理为对照的3.314倍,二者呈现显著性差异。采用DCCA法对4个处理进行环境相似度分类,结果显示,P和NPM处理、CK和NP处理分别构成了2个相似类群;4个处理和12个环境因子的关联(CCA)分析表明,不同处理中的氨氧化微生物活跃度以及氨氧化过程强度表现为处理NMP>NP>CK>P;不同环境因子和不同施肥处理生境相似度分布存在不同的关系,其中反映氨氧化过程的硝态氮含量、氨氧化细菌和氨氧化古菌丰度,以及代表微生物生长主要环境因素的pH值、含水量、全氮和有机碳含量与不同施肥处理导致的生境相似度的分布关系最为紧密。     

甘肃狭啮卵在花椒园中的空间分布型及抽样技术

应用6种分布型指数法分析判定了甘肃狭啮Stenopsocus gansuensis卵在花椒园中的空间分布型,利用Taylor幂法则和Iwao回归方程分析聚集原因,结果表明,田间甘肃狭啮卵呈聚集分布,kc值为2.7934,符合负二项分布;其种群聚集原因是由本身行为习性所致。在此基础上,应用Iwao的理论抽样数模型建立了甘肃狭啮卵的田间理论抽样数公式：N=（t/D）2（1.7673）/m＋0.19887;根据Kuno新的序贯抽样法通式建立了该种群序贯抽样公式：Tn=1.7673/（D20-0.19887/n）。