北美温带玉米杂交种选系的遗传多样性研究

利用SSR标记对北美温带玉米杂交种选育的24个自交系和我国生产应用的10类骨干代表系进行遗传多样性评价。结果表明,54对SSR引物在48份玉米自交系间共检测到290个等位基因变异,每对引物检测出3~9个等位基因,平均为5.4个。每个位点的多态性信息量(PIC)变化于0.29~0.86之间,平均为0.70。标记索引系数(MI)变化范围0.86~7.45,平均为3.86。供试北美温带选系和其他类群的玉米种质均具有较丰富的遗传多样性。3个杂交种选系的遗传相似系数中3号选系最小(0.776),说明3号较其余两个杂交种选系的遗传差异大。根据SSR标记聚类分析、主坐标分析和遗传进化分析结果表明,北美温带选系和其他种质的48份玉米自交系划分为6大类群,分类结果与系谱来源基本一致。     

拉丁美洲和加勒比地区主要竹种资源与利用

拉丁美洲和加勒比地区是世界主要的竹资源分布区,以瓜多竹为代表的560多竹种资源占全球竹种的33%,其中巴西、哥伦比亚、秘鲁、厄瓜多尔、墨西哥等国竹林面积和竹种数量位居该地区前列。与亚洲相比,拉丁美洲和加勒比地区现代竹产业发展起步较晚,规模和效益有限。面向未来,该区竹资源主要分布国家的政府正在制定和实施相关政策和战略,助力竹区发展经济、缓解贫困和保护环境。     

Land Use – Land Cover Conversion, Regeneration and Degradation in the High Elevation Bolivian Andes

Regional land-cover change affects biodiversity, hydrology, and biogeochemical cycles at local, watershed, and landscape scales. Developing countries are experiencing rapid land cover change, but assessment is often restricted by limited financial resources, accessibility, and historical data. The assessment of regional land cover patterns is often the first step in developing conservation and management plans. This study used remotely sensed land cover and topographic data (Landsat and Shuttle Radar Topography Mission), supervised classification techniques, and spectral mixture analysis to characterize current landscape patterns and quantify land cover change from 1985 to 2003 in the Altiplano (2535–4671 m) and Intermediate Valley (Mountain) (1491–4623 m) physiographic zones in the Southeastern Bolivian Andes. Current land cover was mapped into six classes with an overall accuracy of 88% using traditional classification techniques and limited field data. The land cover change analysis showed that extensive deforestation, desertification, and agricultural expansion at a regional scale occurred in the last 20 years (17.3% of the Mountain Zone and 7.2% of the Altiplano). Spectral mixture analysis (SMA) indicated that communal rangeland degradation has also occurred, with increases in soil and non-photosynthetic vegetation fractions in most cover classes. SMA also identified local areas with intensive management activities that are changing differently from the overall region (e.g., localized areas of increased green vegetation). This indicates that actions of local communities, governments, and environmental managers can moderate the potentially severe future changes implied by the results of this study.     

美国西加云杉出国考察报告

简要介绍了西加云杉的生物生态学特性及其生境条件 ,并提出了该树种引种的研究方向。     

The potential of intercropping as an alternative land use system in temperate North America

The success of many intercropping systems in North America is attributable to the generation of a short term return from an agricultural crop during the early, unprofitable years of a longer term crop that is fruit, nuts or wood. This highly-efficient use of land and related profitability are important not only in the development of intercropping systems per se, but also in other applications which have tremendous potential independent of profitability. For example, intercropping can be effectively used during the establishment phases of hardwood plantations where it is essential to have a high level of weed control, the costs of which are often recovered with the agricultural production. Intercropping can also be used to grow trees rapidly and with a form that can be easily integrated into recreational or park situations, or urban fringe areas. In an urban context, intercropping can be used to grow trees in agricultural areas that are likely to be developed where traditional forestry options are not appropriate and the value of younger, thrifty trees may enhance property values far in excess of the cash value of the wood.     

Agroforestry systems in North America

Agroforestry systems in North America vary widely in terms of components (tree, forb, graminoid, and shrub species) and outputs. Most of the agroforestry systems used in North America have emphasized wood and livestock production. The objective of each system has been to produce annual and long term economic returns and sustainable yields. Inputs such as fossil fuels, fertilizers, herbicides and pesticides are relatively low compared to those used in conventional agriculture.Major agroforestry system types in each of eight North American regions are described. The major species used as vegetational components in each system are enumerated by region. The numerous variations in how these components are mixed have created an almost endless number of actual systems. Management problems and solutions, economic concerns, and system comparisons have also been addressed for each region.     

Landowner perceptions and the adoption of agroforestry practices in southern Ontario,Canada

A mail-out survey questionnaire was developed by the Agroforestry group at the University of Guelph to determine the level of awareness and interest in the adoption of agroforestry systems by landusers from four townships in Wellington County, Ontario. The questionnaire investigated: (1) the current level of knowledge regarding windbreaks, woodlots and plantations, intereropping, riparian plantations and silvipasture, (2) the present level of participation in each of these systems on-farm, (3) the perceived benefits and/or drawbacks of each of these initiatives with respect to total farm income, income diversity, land rehabilitation, land value/equity, soil/water conservation, labour intensity, overhead and return on the term of investment.The majority of respondents were familiar with conventional agroforestry systems such as windbreaks and woodlots/plantations (80%, 62% respectively), therefore the level of interest in the adoption of these practices was significant (74%, 66% respectively). Response rates were lower for silvipasture, riparian plantations and intercropping, most likely as result of the low level of familiarity with these practices (20%, 32%, 4% respectively). Respondents commented that agroforestry systems would have a neutral effect on farm income, and would increase land stewardship. In some cases, interested landusers indicated a willingness to participate in agroforestry systems even though they anticipated increases in overhead and labour intensity; however, this was only true if they held land stewardship as a priority. Landusers were more concerned with the economic aspects of agroforestry, as a determinant to the future adoptability of particular practices. Age, gender, farm operation and farm size were not correlated with the adoption of agroforestry systems.The success of agroforestry programs on farms in the study area is largely dependent on the attitudes and willingness of landusers to participate in non-traditional agricultural systems.     

Mapping the territory: agroforestry awareness among Washington State land managers

There is growing interest in research to develop potential agroforestry models for temperate climates. In Washington State, recent studies and anecdotal information suggest that agroforestry is already employed by land managers, and if so, this experience should inform future research efforts. Because this population is not well defined, a mail survey was designed to: 1) Assess Washington land manager awareness of agroforestry, 2) assess perceptions of agroforestry as a land management tool, 3) assess the perceived potential opportunities or obstacles for land managers to practice agroforestry, and 4) identify landowner groups believed to be practicing agroforestry in Washington State.Three groups of land managers were surveyed: employees of the Soil Conservation Service (SCS), Washington State University Cooperative Extension Service (WSUCE) and OTHER, consisting of university faculty, private land managers, State and Federal land managers and owners of small natural resource businesses.Agroforestry was not a new concept for most (94%) respondents, further 55% of those familiar with agroforestry were practicing agroforestry or providing advice to landowners who were practicing agroforestry. Use in (government mandated) soil conservation plans on farmland (100% of all respondents) was the most frequently cited potential application for agroforestry in the state followed by range and pasture land and managing non-commercial forest land (both 84%), use on commercial forest plantation (83%) and fruit and nut orchards (61%).Diversifies land use (25%), enhanced productivity (18%), aesthetics (13%) and income diversity (13%) were the four most frequently cited potential advantages to practicing agroforestry. Lack of information (28%), lack of technical assistance (18%), establishment costs (14%) and not an established practice (14%) were the most frequently identified potential obstacles to practicing agroforestry. Respondents suggested there is great potential for application of agroforestry throughout the state, and non-industrial private forest land owners were selected for future study of this potential.     

West Nile virus in North America: perspectives on epidemiology and intervention

West Nile virus (WNV) invaded New York in 1999 and rapidly swept across the North American continent to the West Coast, north into southern Canada and south into Latin America, with minimal genetic change. Regional epidemics in equines and humans typically have included a year of viral introduction with minimal activity, successful overwintering, explosive amplification to epidemic levels the following year and then rapid subsidence. Overwintering possibly included long-term mosquito or avian infections, continued low-level transmission at southern latitudes and dispersal by south-north migrants. Explosive amplification has been associated with infections in several corvid species and other urban birds that produce elevated viremias capable of efficiently infecting even moderately susceptible mosquito species. Intervention has included mass vaccination of equines, and proactive and reactive mosquito control. Proactive mosquito control in areas with established infrastructure has been successful in reducing case incidence.     

美国高校学生宿舍管理及对我国的启示

学生宿舍管理是学生工作的重要组成部分,学生的学业表现在很大程度上受到其周围环境,特别是居住环境的影响,科学合理的组织管理构架、高素质的工作队伍、安全舒适的住宿环境、配套完善的基础设施,能有效提高学生的宿舍管理、教育、服务等整体功能,使其成为促进学生成长的重要场所,更好地做好学生宿舍管理、服务育人.