Integration of soil, crop and weed management in low-external-input farming systems

Greater adoption and refinement of low-external-input (LEI) farming systems have been proposed as ways to ameliorate economic, environmental and health problems associated with conventional farming systems. Organic soil amendments and crop diversification are basic components of LEI systems. Weed scientists can improve the use of these practices for weed management by improving knowledge of four relevant ecological mechanisms. First, multispecies crop rotations, intercrops and cover crops may reduce opportunities for weed growth and regeneration through resource competition and niche disruption. Secondly, weed species appear to be more susceptible to phytotoxic effects of crop residues and other organic soil amendments than crop species, possibly because of differences in seed mass. Thirdly, delayed patterns of N availability in LEI systems may favour large-seeded crops over small-seeded weeds. Finally, additions of organic materials can change the incidence and severity of soil-borne diseases affecting weeds and crops. Our research on LEI sweetcorn and potato production systems in central and northern Maine (USA) suggests that these mechanisms can reduce weed density and growth while maintaining crop yields. Low-external-input farming systems will advance most quickly through the application of interdisciplinary research focused on these and other ecological mechanisms.     

Reconciling poverty alleviation with reduction in fisheries capacity: boat aid in post-tsunami Aceh, Indonesia

Abstract  The tremendous loss of life and assets resulting from the 2004 tsunami dealt a devastating blow to the coastal communities of Aceh Province, Indonesia. An assessment of the fishing fleet structure pre- and post-tsunami, including associated pattern in boat aid, in 15 coastal communities was conducted and compared with data on boat relief efforts over 17 districts of the Province. Aid was found to be not proportionally allocated to losses incurred by communities and was in many cases below what could be seen as a trend toward overcapacity. The distribution of aid appeared to be done without consideration of the former structure of the fleet, which changed significantly over time (pre- and post-tsunami), and resulted in a new fleet of reduced diversity with a strong focus on the smaller boat categories. If this situation perpetuates after the initial post-disaster period, it may further exacerbate the pre-existing economic and geographic marginalisation of some remote communities, and reduce the capacities of the fleets to diversify and develop multi-species harvesting strategies; thus, increasing the risk of ecologically unsustainable exploitation in near shore areas.     

Cropping systems modify soil biota effects on wheat (Triticum aestivum) growth and competitive ability

Plants alter soil biota which subsequently modifies plant growth, plant–plant interactions and plant community dynamics. While much research has been conducted on the magnitude and importance of soil biota effects (SBEs) in natural systems, little is known in agro‐ecosystems. We investigated whether agricultural management systems could affect SBEs impacts on crop growth and crop–weed competition. Utilising soil collected from eight paired farms, we evaluated the extent to which SBEs differed between conventional and organic farming systems. Soils were conditioned by growing two common annual weeds: Amaranthus retroflexus (redroot pigweed) or Avena fatua (wild oat). Soil biota effects were measured in wheat (Triticum aestivum) growth and crop–weed competition, with SBEs calculated as the natural log of plant biomass in pots inoculated with living soil divided by the plant biomass in pots inoculated with sterilised soil. SBEs were generally more positive when soil inoculum was collected from organic farms compared with conventional farms, suggesting that cropping systems modify the relative abundance of mutualistic and pathogenic organisms responsible for the observed SBEs. Also, as feedbacks became more positive, crop–weed competition decreased and facilitation increased. In annual cropping systems, SBEs can alter plant growth and crop–weed competition. By identifying the management practices that promote positive SBEs, producers can minimise the impacts of crop–weed competition and decrease their reliance on off‐farm chemical and mechanical inputs to control weeds, enhancing agroecosystem sustainability.     

西方经济学多元化教学改革模式初探

随着社会改革和经济社会转型的不断深入,普通高校中西方经济学的教学工作正面临着一个重要的历史命题———如何对教学工作和教学模式进行改革,使其适应时代发展的需要,为社会提供适合社会要求的智力资源。本文以此为契机,对西方经济学多元化教学模式的改革问题进行了研究。旨在通过本文的工作,为西方经济学的教学工作提供一定的思想借鉴。     

日本农业女性参与农业及农村发展的现状与分析

日本农业就业人口的半数以上是女性,女性在担负着操持家务、育儿和赡养老人的同时,在农业经营以及农村第二、第三产业方面发挥着重要的作用。而且近年来涌现在农产品加工、销售、流通、观光农园、农家饭庄等与"食"文化相关领域的农村女性呈增长态势,对区域农业的多元化发展和农村的活化方面做出了积极的贡献。中国应该借鉴日本的经验,有意识地创造有利于发挥和释放女性能力的就业环境,不断拓展女性在农业、农村的活动领域,促进当地农业、农村经济的发展。     

中国上市公司多元化经营绩效的实证分析

通过随机抽样,计算我国57家上市公司1998年-2002年的平均盈利指标和风险指标,根据各公司多元化熵值的大小对样本总体进行分组,分析多元化程度对企业绩效的影响.研究发现1.多元化程度越高,公司的平均净资产收益率越高;2.多元化经营降低了公司收益率的波动水平;3.资产规模越小的公司越倾向于选择多元化经营.     

蝶形花科植物叶绿体基因组研究进展

被子植物叶绿体基因组比较保守,但豆科植物中蝶形花科叶绿体基因组却表现出高度分化的特征.通过综述蝶形花科叶绿体基因组在进化过程中多个基因/内含子丢失、倒置的发生对基因排列顺序变化的影响,不同物种间或同一物种中不同基因间进化速率的差异等特征,推测重复序列的存在可能是其出现高度分化的一个重要原因.目前已测序的蝶形花科植物叶绿体基因组的数量有限,叶绿体基因组高度分化的内部机制尚不完全清楚.随着越来越多的蝶形花科植物叶绿体基因组测序的完成,可以深入探讨叶绿体基因丢失的机制及影响;通过开发高变的叶绿体基因标记,可对蝶形花科进行近缘物种的系统学研究.     

从无梁楼盖到植物景观——探求植物的空间设计

以建筑的空间概念指导室外植物种植,并从宏观的空间概念、微观的空间特质以及空间的变化等方面对植物塑造空间的手法进行了探讨。     

The origin,evolution, cultivation,dissemination, and diversification of Asian and African rices

Summary Available evidences drawn from biosystematics, evolutionary biology, biogeography, archaeology, history, anthropology, paleo-geology and paleo-meteorology are pooled to reconstruct the series of events that led to the cosmopolitan cultivation of the Asian cultivated rice (O. sativa) and the regionalized planting of the African cultigen (O. glaberrima) in West Africa. The genus Oryza originated in the Gondwanaland continents and, following the fracture of the supercontinent, became widely distributed in the humid tropics of Africa, South America, South and Southeast Asia, and Oceania. The two cultivated species have had a common progenitor in the distant past. Parallel and independent evolutionary processes occurred in Africa and in Asia, following the sequence of: wild perennialwild annualcultivated annual. The weed races also contributed to the differentiation of the cultivated annuals. The corresponding members of the above series are O. longistaminata Chev. et Roehr., O. barthii A. Chev., O. glaberrima Steud., and the stapfii forms of O. glaberrima in Africa; O. rufipogon Griff., O. nivara Sharma et Shastry, O. sativa L., and the spontanea forms of O. sativa in Asia.The differentiation and diversification of the annuals in South Asia were accelerated by marked climatic changes following the last glacial age, dispersal of plants over latitude or altitude, human selection, and manipulation of the cultural environment.Cultivation of rice began in many parts of South and Southeast Asia, probably first in Ancient India. Cultural techniques such as puddling and transplanting were first developed in north and central China and later transmitted to Southeast Asia. Wetland culture preceded dryland culture in China, but in hilly areas of Southeast Asia, dryland cultivation is older than lowland culture. The planting method progressed from shifting cultivation to direct sowing in permanent fields, then to transplanting in bunded fields.Widespread dispersal of the Asian cultigen led to the formation of three eco-geographic races (Indica. Sinica or Japonica, and Javanica) and distinct cultural types in monsoon Asia (upland, lowland, and deep water). Varietal types changed readily within the span of a millenium, largely due to cultivators' preferences, socio-religious traditions, and population pressure. Genetic differentiation developed parallel to the ecologic diversification process.The African cultigen developed later than the Asian cultigen and has undergone less diversification. The wild races in South America and Oceania retain their primitive features mainly due to lack of cultivation pressure or dispersal.Both the African and Asian rices are still undergoing evolutionary changes at habitats where the wild, weed, and cultivated races co-exist.     

台湾中原大学建筑系研究生教育——赴台湾交流学习浅谈

台湾中原大学建筑系隶属于设计学院．从1960年代建系至今,根据其教学特点的演变其发展历程大致可以分为四个阶段。首创了以中国传统建筑为主耍研究内容钓支资纽,形成了独特的研究生建筑教育模式,并且发展了多元化的建筑教育理念。