准格尔盆地西北缘一次寒潮天气特征分析

通过分析2011年2月下旬准格尔盆地西北缘发生的一场寒潮天气,总结了形成这次天气的环流背景、中低层温度场及冷平流垂直变化特征.结果表明,欧洲脊主体稳定,脊顶缓慢东南垮,西伯利亚槽逆转南压西伸,槽前形成强盛的西南急流,使天气前期区域气温快速上升.槽后西北风带风速不断加强,输送高纬冷空气南下堆积,冷平流快速进入中低层大气,强冷空气在近地面猛烈暴发,是形成此次寒潮天气的主要成因.     

2014年大豆市场形势分析与2015年展望

预计2014年国内大豆种植面积继续下降,但黑龙江由于春涝在连续5年下降后首次增加。由于黄淮海流域部分地区大幅减产,预计全国产量比上年略减。2014年,国内大豆价格先降后升,国际大豆价格先涨后跌,价差创历史最高纪录。大豆进口继续增加,进口量有望接近7 000万t,再创纪录已成定局。展望2015年,全球大豆供给充裕,国际大豆价格难掀波澜,国内大豆价格易跌难涨。     

Vegetation development of sown grass margins in arable fields under a countrywide agri-environment scheme

Farmers were paid to establish 6 m wide sown grass strips in arable field margins under the Countryside Stewardship Scheme in England, UK. One hundred and sixteen sites in eight regions were surveyed to determine if grass margins had been established successfully and the extent to which they were colonised by forbs. Sown margins had more grass and fewer weed species than naturally regenerated sites. Grass margins contrasted with normally cropped sites, having greater species richness of grasses, forbs and perennials and more bird, butterfly larva and bumblebee foodplants. Mesotrophic grassland forbs were scarce in margins established from basic grass seed mixtures but significantly more abundant if included in the seed mixture. Annuals were more prevalent in sites up to 2 years old but species composition was not related to age in sites over 2 years old. Variation partitioning showed that overall species composition was related to seed mixture type, region and soil properties but there was little overlap in the variation explained by these environmental variable sets. Habitat context and management practices did not explain any variation in species composition. Perennial grassy vegetation was established successfully using basic grass seed mixes but only competitive species colonised subsequently. Diverse seed mixtures containing mesotrophic grassland forbs merit support in agri-environment schemes because they do enhance the botanical diversity of sown grass margins.     

The prospects of reduced tillage in tef (Eragrostis tef Zucca) in Gare Arera, West Shawa Zone of Oromiya, Ethiopia

Soils in Ethiopia are traditionally ploughed repeatedly with an oxen-drawn plough before sowing. The oxen ploughing system exposes the soil to erosion and is expensive for farmers without oxen. This study was undertaken to assess agronomic and economic impacts of alternative, reduced tillage methods. Field experiments were carried out on a Vertisol and a Nitisol for 2 years to study the effect of zero tillage, minimum tillage, conventional tillage, and broad bed furrows (BBF) on the yield of tef (Eragrostis tef Zucca). No significant differences in tef biomass and grain yields were observed between the treatments on both soils in the first year. In Nitisol in the second year, yield was lower in the zero tillage treatment as compared to the other treatments. No difference in yield was observed between single plough, conventional, and BBF. On Vertisol, the yields were higher in BBF as compared to the other treatments. The yields on Vertisol were 1368, 1520, 1560 and 1768 kg ha⁻¹ for the zero tillage, minimum tillage, conventional tillage and BBF treatments respectively. More than twice as much grass weed was observed on zero tillage treatment as compared to the BBF treatment on both soils. Zero tillage gave the lowest gross margin on both soils whereas BBF gave the highest gross margin. The gross margin on Nitisols for the zero tillage and BBF treatments were −108 and 1504 Birr/ha respectively and corresponding numbers for the Vertisol were 520 and 1924 Birr ha⁻¹. On Vertisol there were no significant difference in gross margin between minimum tillage and conventional tillage. Minimum tillage is an interesting option on Vertisols, particularly for female-headed households as it reduces the tillage cost. It may also improve overall productivity of the farming system because it allows partial replacement of oxen with cows and reduces soil erosion.     

矿区沉陷地复垦与生态重建研究

合理调控和稳定边缘带是干旱区绿洲生态系统可持续发展的重要途径.针对部善绿洲边缘带天然植被衰退、生态功能下降等问题,采用实地调查和收集相关调研成果相结合的方法,在初步查明天然植被现状及存在问题、分析退化原因的基础上,探讨了鄯善绿洲边缘带天然植被的保育途径,认为主要应从加强现有植被的保护,加强人工林的培育,采用必要的经济手段等方面来实施.     

中国木质家具出口的二元边际及其影响因素分析

木质家具出口在中国木质林产品出口贸易中占据重要地位。对1996-2015年中国与15个主要木质林产品贸易伙伴的木质家具出口数据进行二元边际分解并对其影响因素进行分析,结果表明:中国木质家具出口贸易的增加几乎完全来自集约边际的贡献;集约边际与目的地市场规模和多边阻力呈正相关,与可变贸易成本和相对劳动生产率负相关;加入世贸组织对集约边际的提升有促进作用。文中结合实证分析结果和木质家具贸易面临的新形势提出了具有针对性的对策和建议。     

网络时代期刊出版标识应标准化和规范化

通过对期刊的封面、条形码和页眉3个出版标识不规范现象的调查,建议网络时代的期刊出版标识应该实现标准化和规范化。     

Promoting the use of home-mixed supplements as alternatives to commercial supplements in smallholder beef production systems in the subhumid region of Zimbabwe

The economic and performance effect of supplementing smallholder cattle by substituting commercial feed with iso-nitrogenous and iso-energetic diets based on alternative protein sources was investigated in two trials. In trial 1, three diets (commercial concentrate, commercial concentrate partially substituted with mucuna, and commercial concentrate partially substituted with lablab–cowpea) compared with veld grass were allocated to 12 cattle in a complete randomised block design. In trial 2, a double complete randomised block design with 40 cattle assigned to four forage legume-based diets, a poultry-based diet and a commercial beef concentrate was carried out. Diets were offered at 1.5% of body weight daily over 56 d. Average daily weight gain (ADWG) was measured weekly in trial 1 and fortnightly in trial 2. In trial 1, ADWG was significantly (p < 0.05) higher for animals on supplements compared with non-supplemented cattle. In trial 2, ADWG was significantly highest on the groundnut stover-based diet and least on the poultry litter diet. Supplementation had a positive effect on ADWG and economic performance of smallholder beef cattle. Substitution of commercial concentrates with alternative protein sources reduced diet costs and significantly improved gross margins.     

Comparative Morphology and Morphometry of Six Biotypes of Bemisia tabaci （Hemiptera： Aleyrodidae） from China

Morphology and morphometry of six biotypes(B,Q,Cv,ZHJ-1,ZHJ-2 and ZHJ-3) of Bemisia tabaci(Gennadius) from China on cotton plants were studied by using microscopes.Nymphal body sizes and characters were measured and observed,especially on the 4th instar(pupal case),including the vasiform orifice,operculum,lingula,length and thickness of anterior and posterior wax margins,width of thoracic tracheal combs.Adult characters of both sexes were investigated including the body size,compound eyes,antennal segments,vasiform orifice,hind tarsi and genitals.The results indicated that differences of some morphological characters or morphometrics were significant among the six biotypes of B.tabaci in China:(1) Pupal sizes of the exotic biotypes(B and Q) were significantly larger than the indigenous biotypes with the following order as B>Q>ZHJ-1>Cv>ZHJ-3>ZHJ-2;(2) for both male and female adults,sizes of all characters investigated in the invading biotypes(B and Q),especially B,were much larger than those of the indigenous ones.