基于美国林务官制度对优化我国森林资源管理方式的思考

介绍了美国林务官制度, 包括林务官的选拔方式、岗位权责以及林务官制度在美国森林资源管理中发挥的作用; 针对我国森林资源管理中存在的-些问题, 指出美国林务官制度对优化我国森林资源管理方式的借鉴作用。     

南美洲和非洲的农业资源及其开发

随着我国经济的快速发展,城市化进程将更进一步,相应的耕地面积也将减少,如何保障我国粮食安全成为一个应长期关注的问题。通过分析南美洲和非洲的土地资源、人力资源、水资源及相关政策,提出了发展海外农业的新观点及建议。     

文化差异对家庭教育的影响——中美家庭教育比较

教育是一种文化现象。传统文化的差异孕育了不同的家庭教育,而不同的家庭教育反映着不同的社会文化内涵。家庭制度、价值取向、民族性格、思维方式是中美家庭教育文化差异的集中体现。借鉴美国家庭教育中的先进理念,转变我国的家庭教育观念,提升家长自身素质,培养儿童的自信心和创造力,营造平等民主的家庭教育氛围有着重要的现实意义。     

Nitrogen fertilization and aspects of fruit yield in a Missouri black walnut alley cropping practice

Increasing nut production through cultural practices is important to landowners for maximizing economic gain from agroforestry plantings. This project studied the effects of applying low rates of nitrogen (N) fertilizer during either the spring or late summer, on pistillate flowers formed, fruits retained, and fruit quality (percentage kernel) in black walnut (Juglans nigra L.) grown under alley cropping management. Treatments consisted of two forms of nitrogen fertilizers (NH₄NO₃ and NaNO₃) applied in mid-April, or mid-August of 1995 and 1996, and a nonfertilized control group. Pistillate flowers counted in May, 1996, showed that fertilized trees, regardless of timing or form of N applied, produced from 2.3 to 3.4 times the number of pistillate flowers as unfertilized control trees. Through the season, the fertilized trees had greater fruit retention, and ended with 2.9 to 4.8 times more walnuts (on a whole tree basis) than nonfertilized control trees. In addition, all fertilizer treatments resulted in increased nut yields from 1995 to 1996, while unfertilized control tree yields decreased approximately 70%. Summer application of fertilizer showed the greatest benefit to kernel weight. Average kernel weights of nuts from the summer-fertilized trees increased from 1995 to 1996, while kernel weight averages from spring-fertilized and nonfertilized trees remained unchanged or decreased. This revised version was published online in June 2006 with corrections to the Cover Date.     

A financial analysis of a small scale Gmelina arborea Roxb. improvement program in Costa Rica

A financial analysis of a small-scale Gmelina arborea improvement program in Hojancha, Guanacaste Province, Costa Rica is described. The program consisted of a clonal seed orchard, made up of ramets of plus-trees, and three progeny tests/seedling seed orchards. A 5% discount rate was used. The total discounted/compounded cost of the program was US$25423. The analysis demonstrated that this outlay would be justified at annual planting rates of between 31 ha per year (at 20% genetic gain in volume) to 125 ha per year (at 5% genetic gain) over the 20-year life of the orchard. These results demonstrate that the implementation of such small-scale, locally-based programs by community-based or locally-orientated organizations may often be justifiable.     

Polymerase chain reaction banding patterns of the 5S rDNA gene as a diagnostic tool for the discrimination of South American mullets of the genus Mugil

The mullets of the family Mugilidae, and in particular the species of the genus Mugil, are characterized by highly conserved morphological features, which hinder taxonomic classification considerably. Given this, the present study aimed to evaluate the efficiency of the 5S rDNA gene – a rapid and low cost genotyping marker – for the discrimination of Mugil species. Variations in the banding pattern permitted the reliable differentiation of four species –Mugil curema, Mugil incilis, Mugil sp. and Mugil hospes– although those of three others (Mugil liza, Mugil platanus and Mugil cephalus) were identical. This suggests that these three forms have diverged very recently, on a time scale that has limited changes in the length of the fragments of the 5S rDNA gene. The results of the study confirm the efficiency of this marker as a diagnostic tool for the identification of Mugil species, and its usefulness for population management and pisciculture, an important economic activity involving this group.     

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.     

美国和加拿大的林业非政府组织建设

介绍了美国、加拿大4个重要林业非政府组织的概况、运作模式和管理制度, 对促进我国林业非政府组织的发展提出了建议。     

北美栎树无性繁殖试验

对引种的北美栎树进行的扦插与嫁接繁殖试验结果表明:柳叶栎、纳塔栎和水栎1年生实生母树上的穗条,具有一定的扦插繁殖潜力。以200×10-6ABT6号处理纳塔栎插穗,生根率达52%;以100×10-6ABT6号处理水栎插穗,生根率达22.0%,以100×10-6ABT6号处理柳叶栎插穗,生根率达70%。但从6年生柳叶栎母树上采穗,并进行相同处理扦插后则不能生根,愈合率仅为7.2%。上述3种栎树的扦插生根能力顺序依次为柳叶栎>纳塔栎>水栎;全光喷雾设施的生根效果优于封闭式扦插。生根剂ABT6号处理优于NAA处理和NAA VB2处理。以麻栎为砧木,对纳塔栎、红栎和水栎等进行春季枝接后,60 d后的成活率分别为47.5%~61.2%,47.5%和13.3%~15.0%,且春季枝接的效果优于秋季芽接。