美国森林健康状况

文章介绍了美国近年来的森林健康状况,指出2000～2002年是50年来美国森林火灾最严重的时期。同时,昆虫和病原体非自然传入也给美国造成了重大损失,乡虫害虫爆发生也是造成其森林危机的一个重要因素;南部阿巴拉契亚山脉的生态系统受到扰乱甚至由此出现了一个新的森林类型。尽管问题多多,但也取得了一定的成果。2002年布什总统签署了《健康森林执行规划》,与《国家森林防火规划》等形成一个森林恢复项目。     

The persistence of secondary forests on colonist farms in the BrazilianAmazon

While slash-and burn farmers convert forest to agriculture, they also regenerate significant areas of secondary fallow forests on their farms. Under what conditions does secondary forest cover persist on slash-and-burn farms? Survey data from Pará, Brazil show that secondary forests occupy 20% of farm area even after a century of settlement. In addition to restoring soil fertility, secondary forests contribute over 20% of farmers' income through products such as charcoal, fruit, game animals and firewood for on-farm processing. Econometric analysis shows that slow rates of population growth and increases in agricultural incomes through on-farm processing of agricultural products enable farmers to maintain long fallows and result in diversified systems compatible with secondary forest cover in the study area. On the other hand, declining agricultural productivity, subsidized credit, declines in the growth rate of secondary forests and policies favoring speculative land acquisition threaten secondary forest persistence. In older settlement areas, secondary forests are often the only forest resource available to the rural poor. Fallow areas should therefore be managed not only for agricultural productivity, but also for conserving forest resources.     

国内外绿豆农药最大残留限量标准对比研究

为了研究农药最大残留限量标准对中国绿豆对外贸易的影响,以中国、国际食品法典委员会(CAC)、欧盟、日本、美国、韩国和加拿大等国家绿豆农药最大残留限量标准为基础,从限量标准数量、限量大小和占比、限量宽松度等方面对比分析中国与贸易国之间的差异.结果发现,中国绿豆农药最大残留限量标准少,共83项,与日本的388项、欧盟的56...     

美国玉米科研生产实践对黑龙江玉米发展的启示

美国是世界上玉米种植面积及产量最多的国家,在玉米的生产、科研及推广等方面的研究都非常的先进和科学,学习借鉴他们的先进技术和经验,对指导中国玉米生产,特别是黑龙江玉米生产具有重要的现实意义。通过对美国中部大平原Iowa和Nebraska玉米的种植、科研和推广等方面的考察与交流,归纳出美国玉米生产情况是:美国玉米耕作与栽培体系更科学,农艺农机结合更紧密,应用综合抗性强的转基因玉米品种和科学合理的肥水管理等,同时,全面向智能化方向发展和提升。从中得出对我国农业及玉米种植的启示是:农机与农艺结合要切合实际,加大保护性耕作推广力度和中低产田改造,培肥地力增加土壤有机质,开展精准农业研究并运用于实践指导生产,加强转基因技术、节水增效技术研发与应用,推动黑龙江土地规模经营,加强农民培训以提高素质,加强对玉米增产潜力和实际产量差异影响因素研究。     

美国内部控制审计最新研究进展及启示

为贯彻《萨班斯·奥克斯利法案}404条款的执行,美国采用了PCAOB（公众公司会计监督委员会）制定的第2号审计准则——《与财务报表审计相整合的财务报告内部控制审计》。通过对第2号审计准则执行情况的反馈和评估,PCAOB于2006年12月提出新的审计准则提案以取代第2号审计准则。在对新准则提案重要条款探讨的基础上,指出了提案与第2号准则的差异,并结合我国实际情况,提出规范我国内部控制审计的系统建议。     

土壤多样性的概念、方法与研究进展

上世纪90年代开始的土壤多样性研究引起多方的兴趣,先后已经有西班牙、中国、美国等国家展开有关内容的研究。文章介绍了土壤多样性的基本概念、计量方法与数学模型及其在国内外的研究现状与最新发展,并对西班牙在爱琴海、美国全国范围以及中国海南岛和山东省的有关研究进展进行了初步评述。国内外研究表明,尽管作为新生事物有其不够完善的地方,土壤多样性研究可为土地利用及规划管理、环境保护、生物保护和自然保护区的设计、自然生态景观的维护和修复等方面提供服务,土壤多样性理论方法在土壤学及其他相关科学中仍具有良好的应用前景。     

Carbon cycling and sequestration opportunities in South America: the case of Brazil

Abstract. A carbon emission inventory of the Brazilian agricultural sector was used to compare greenhouse gas emissions with estimated carbon offsets promoted by two main changes in agricultural management: the replacement of conventional tillage by no-tillage and the cessation of annual burning in sugar cane production. Using the IPCC revised 1996 guidelines for national greenhouse gas inventories, we estimate that 12.65 Mt C are emitted annually from agricultural land in Brazil. Ongoing conversion of conventionally tilled land to no-tillage currently accumulates 9 Mt C yr⁻¹. Industrial by-products like alcohol and bagasse from sugar cane processing substitute fossil fuel for transportation and power generation offsetting 10 and 8 Mt C yr⁻¹, respectively. An additional opportunity for 0.53 Mt C yr⁻¹ sequestration is presented by avoiding burning before harvesting of sugar cane. These data show that there could be almost full compensation between sources and sinks/offsets in the agricultural carbon cycle. There is a great opportunity to achieve this mitigation benefit because the adoption of new technologies is increasing rapidly.     

The evidence for the extent of N.I. Vavilov's new world Andean centres of cultivated plant origins

Vavilov's ideas on New World centres of crop plant diversity are reviewed and the development of his ideas from 1926 to 1940 are described. More recent collecting work and taxonomic studies by the author confirm largely the delimitation of the American gene centres suggested by Vavilov, even in regard to details, e.g. within Bolivia.     

Sucrose avoidance by American robins (Turdus migratorius): Implications for control of bird damage in fruit crops

Altering the relative sugar content in fruit is a potential alternative to chemical, aural and visual repellents to control bird damage to cultivated fruit crops. Some frugivorous birds, such as the American robin (Turdus migratorius), lack the digestive enzyme sucrase, and therefore cannot digest sucrose. It was predicted that robins would avoid consumption of foods that contain sucrose. When offered sweetened agar cubes that contained glucose, fructose, sucrose, or a hexose mixture, total consumption was significantly lower and faecal sugar concentration higher in the sucrose tests. In tests involving two sugars, mean total consumption was reduced when sucrose was eaten. Development of high-sucrose fruits warrants further investigation as a means to mitigate bird damage to certain fruit crops.