油桐北缘产区优树选择及其主要性状描述

为推进油桐产业的快速和规模化发展,解决北缘地区油桐良种缺乏的问题,2011年以来,在对安徽大别山区的桐城和金寨等地的油桐种质资源调查的基础上,开展油桐优良单株选择工作,经初选、复选和决选,最终选择出5株油桐优良单株。所选5个优株雌雄花比例均在1:10以内,属于典型的少花花序类型;丛果性除"金寨2号"稍弱外,其他4株丛果性均较强,果大皮薄,光滑整齐,粒饱仁满,种仁含油率均在50%以上,2年的年均鲜果产量在1.25 kg·m-2以上,各项指标均达到了我国油桐优树的选择标准。以上油桐优树的选出为北缘地带发展油桐提供了良种培育的基础。     

青藏高原东缘3种次生林优势种的种群结构与数量动态

【目的】以青藏高原东缘甘肃南部3种主要次生林为研究对象,探讨其优势种种群结构和数量动态。【方法】选择具有代表性的辽东栎、红桦和糙皮桦种群,各设置8块40 m×40 m的样地,对样地内所有树木进行每木检尺,以测定的胸径数据为基础,以径级代替龄级,将胸径＜3 cm作为Ⅰ龄级,其后以4 cm为标准进行龄级划分,统计各龄级个体数量并进行相关整理后,分析各种群的龄级结构,编制包括死亡率（q_x）、消失率（K_x）和平均期望寿命值（e_x）等参数在内的种群静态生命表,绘制存活曲线,计算考虑外部干扰时的种群数量变化动态指数（Ｖ_pi）、不考虑外部干扰时的种群数量变化动态指数（V′_pi）和对外界干扰所承担的风险概率指数极大值（P_max）,最后对未来经过2,4,6,8个龄级后各种群的数量动态进行时间序列预测,以揭示青藏高原东缘甘肃南部3种次生林优势种的种群现状、种群结构及预测种群未来发展趋势。【结果】① 辽东栎、红桦和糙皮桦3种次生林种群Ⅰ龄级幼苗数量不足,均以Ⅱ龄级幼苗数量最多,分别占种群个体总数的43.62%,30.07%和43.30%;其后随着龄级的增大,种群个体平稳下降,虽然群落为稳定型,但是林木径级较小,各龄级个体数分布不合理。② 辽东栎、红桦、糙皮桦种群的q_x和K_x在Ⅰ龄级最大,q_x分别为78.0%,72.0%和76.2%,K_x依次为151.3%,127.3%和143.5%,且随着龄级的增加,q_x和K_x均逐渐减小;各种群e_x随着龄级增加先增大后减小,辽东栎和红桦均在Ⅵ龄级最大,糙皮桦在Ⅴ龄级最大;种群结构均呈增长型,且存活曲线趋近于Deevery-Ⅲ型。③ 3种次生林种群结构的V_pi大于V′_pi且均大于0,P_max也均大于0,说明 3种次生林均属于对外界干扰敏感的增长型种群。④ 时间序列预测结果表明,未来经过2,4,6,8个龄级后,各种群个体发展呈增长趋势,但辽东栎和红桦种群在发展过程中存在波动性,表现出前期略减、后期稳定的特征。【结论】3种次生林种群结构和发展趋势均呈稳定增长型,但是Ⅰ龄级幼苗数量不足,应采取禁牧、禁采等措施,保护幼苗成活,保证种群的更新发展。     

沿江双季稻北缘区机插早稻的超高产群体特征

【目的】研究安徽沿江双季稻北缘区不同机插高产早稻品种产量差异及超高产品种的群体共性特征,为品种选育与精确定量栽培提供参考。【方法】试验于2018—2019年在安徽庐江进行,采用前期筛选获得的9个高产早稻品种为供试材料,分析不同品种的产量及构成、干物质积累、叶面积指数、有效光截获和利用率的差异。【结果】不同高产品种的产量间存在显著差异,通过聚类分析可进一步分为超高产（9.1—9.5 t·hm ^-2）、更高产（8.1—8.6 t·hm ^-2）和高产（7.6—7.8 t·hm ^-2）3种类型。超高产类型品种较更高产和高产类型品种显著提高了每穗粒数、颖花量和千粒重。超高产类型品种的平均日产量为82.4 kg·hm ^-2·d ^-1,分别较更高产和高产类型品种提高10.2%和19.8%。干物质积累量是不同类型品种产量差异的主要原因,与更高产和高产类型品种相比,超高产类型品种显著提高水稻中后期的阶段干物质积累量18.3%—21.4%。超高产类型品种具有更高的中后期有效光截获量和光截获利用效率,分别与其高的叶面积指数和库容量有关。相关性分析表明,穗分化期和抽穗期群体有效光截获量分别与每穗粒数和千粒重呈显著正相关,且超高产类型品种具有更高的响应效率。另外,与更高产和高产类型品种相比,超高产类型品种显著提高抽穗期总粒重/叶4.1%—11.3%,这与其高的中后期光截获利用率密切相关。【结论】沿江双季稻北缘区机插早稻品种适宜选用叶面积指数高（穗分化期5.6—6.0、抽穗期7.1—7.3）、穗粒数多（124—132）、千粒重高（25.8—27.0 g）,且日产量为80.8—83.7 kg·hm ^-2·d ^-1的品种,可获得超高产水平（>9.0 t·hm ^-2）。     

Evaluating the merits of climate smart technologies under smallholder agriculture in Malawi

The merits of three climate smart agriculture (CSA) technologies implemented by farmers were assessed in Machinga district of Malawi with respect to their soil quality and maize yield effects. Data were collected from farms implementing the three CSA technologies, namely conservation agriculture (CA), maize–pigeonpea (Maize-PP) intercrops and a local organic and inorganic soil amendment known as Mbeya fertilization (Mbeya-fert), from 2018 to 2019. With respect to resilience and adaptation, particulate organic matter, soil organic carbon (SOC), N, P, K, Ca and Mg all significantly improved while bulk densities were lowered under the three CSA systems. Higher annual biomass inputs and improved water infiltration from the Maize-PP intercrops were observed. With respect to productivity, CA and Mbeya-fert improved maize yields by 51 and 19%, respectively, compared to conventional farmer practices. With regard to climate change mitigation, increases in measured SOC in the top 20 cm depth compared to the conventional farmer practices amounted to 6.5, 12 and 10.5 t C ha⁻¹ for CA, Mbeya-fert, and Maize-PP intercrops, respectively, over a period of 2–6 years. This suggests higher potential for carbon sequestration from CSA technologies. Furthermore, use of drought tolerant varieties, timely weeding and optimum plant populations, increased productivity. Improved gross margins from CSA practices were also apparent. Thus, employing these CSA technologies could enable farmers to be more resilient, productive and adapt better to climate change shocks leading to improved food security and livelihoods.     

黄土丘陵沟壑区沟沿线边缘植被特征初步研究

 通过对黄土丘陵沟壑区安塞纸坊沟沟沿线边缘植被特征的调查,共发现隶属26科的66个物种,其中豆科、禾本科和菊科物种分别占19.70%1、5.15%和13.64%;物种中出现最多的是多年生草本,其次依次是1年生草本、灌木、小灌木、乔木、藤本和小乔木,其中灌乔物种多为主要物种且多为当地优势灌木虎榛子和酸枣等,指示着研究区植被恢复的方向;调查植物种基本包含了陕北黄土高原森林草原带次生演替各个阶段的主要植物种,是研究区次生演替的一个缩影;从沟沿线边缘植被的分布看,灌木远多于草本,其中以灌木为主的沟沿线区段植被的宽度、盖度均比以草本为主的沟沿线区段大,沟沿线防蚀效益较好。     

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.     

基于参考机的单机等面积暂态稳定分析

提出了相对参考机的单机稳定裕度评估方法.研究了单一机组功角曲线的表达方式，将多机系统中单机功角曲线表达为本机相对参考机转子角度的函数，提出了基于泰勒级数的功角曲线预测拟合方法.提出了稳定裕度的预测评估方法与事后评估方法，比较了事后评估与预测评估所得稳定裕度的差异.SGEAC方法在判别系统是否稳定时没有任何假设，不需要进行动态二群的识别.实例验证了所提方法的有效性.     

Management of newly established field margins on nutrient-rich soil to reduce weed spread and seed rain into adjacent crops

We studied the effect of different ways to establish and to maintain unfertilised field margins on the development of potential weeds and seed dispersal into adjacent crops. Plant communities in field margins either developed spontaneously or were sown with different seed mixtures of grasses and forbs. Margins were mown twice a year and the cuttings were either removed or left in situ. Three years after establishment, the importance of the unsown rhizomatous species Elytrigia repens and Urtica dioica was significantly higher in the unsown community or when cuttings were not removed after mowing. Seed dispersal from the margin into adjacent crops was important in the unsown community during the first year after establishment. Between 82% and 99% of the seeds were disseminated within 4 m from the margin strip. Overall risk of contaminating the adjacent crop with weeds originating from the field margin strip was concentrated within a few metres of the crop edge. In order to minimise the dissemination of weed species and invasion by noxious vegetatively propagated weeds on nutrient‐rich land, it is recommended that field margins are established by sowing and cuttings removed after each cut.     

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.     

近期中国农产品贸易特点与展望

近期中国农产品贸易保持较快增长,进口增速反弹,出口基本平稳,贸易逆差扩大。谷物、油籽、乳制品等进口大幅增加,棉花、食糖、植物油等进口下降,但仍保持高位,水产品、蔬菜、水果等优势农产品出口小幅增加。进口大幅增加的主要原因是国内需求强劲增长和国内外农产品价差扩大。预计2014年中国大宗农产品进口将保持较高水平,需要妥善应对进口压力。