美国食用菌产业发展报告

通过利用美国农业部、农业统计局及相关行业网站发布的产业数据、新闻报道和研究报告,对美国食用菌产业的变化趋势及其原因进行梳理.结果发现,随着生产效率的提高美国食用菌产量和产值逐年提高,但通过不断的兼并收购,食用菌生产者的数量明显下降.在政府组织和行业自发的行业组织和协调下,美国食用菌行业竞争有序,食用菌价格稳定,食用菌产...     

Foliar nematode,Litylenchus crenatae ssp. mccannii,population dynamics in leaves and buds of beech leaf disease‐affected trees in Canada and the US

A foliar nematode, Litylenchus crenatae ssp. mccannii, is associated with beech leaf disease (BLD) symptoms. Information about the types of tissues parasitized and how nematode populations fluctuate in these tissues over time is needed to improve surveys as well as understand the nematodes role in BLD. During this study, the nematode was detected throughout the known range of BLD by researchers at both Canadian and US institutions using a modified pan method to extract nematodes. Monthly collections of symptomatic and asymptomatic leaves during the growing season (May–October), and leaves and buds between growing seasons (November–March), revealed that nematodes were present in all tissue types. Progressively larger numbers of nematodes were detected in symptomatic leaves from Ohio and Ontario, with the greatest detections at the end of the growing season. Smaller numbers of nematodes were detected in asymptomatic leaves from BLD‐infected trees, typically at the end of the growing season. The nematode was detected overwintering in buds and detached leaves. The discovery of small numbers of nematodes in detached leaves at one location before BLD was detected indicates that nematodes may have been present before disease symptoms were expressed. Other nematodes, Plectus and Aphelenchoides spp., were infrequently detected in small numbers. Our findings support the involvement of the nematode in BLD and indicate that symptoms develop only when certain requirements, such as infection of buds, are met. We also found that the nematode can be reliably detected in buds and leaves using the modified pan extraction method.     

欧美国家针叶树容器苗生产与启示

针叶树是芬兰、瑞典、挪威、美国、加拿大等欧美国家主要的商品林树种。容器苗是针叶树重要的育苗类型。与裸根苗比较,容器苗具有育苗周期更短、造林季节可延长、苗木适应性更广、苗木质量更一致的优点。因此,容器育苗成为精准林业发展的必然趋势。为了借鉴欧美容器育苗的技术方法,提高我国容器苗的质量,为我国针叶树容器苗发展提供参考,文中主要从4个方面综述了欧美国家检测与提高苗木质量的方法,即列举了针叶树常用的苗木质量检测指标,总结了育苗容器与育苗基质的改良进展,介绍了养分、水分、光照与温度等培养条件的优化手段,简要概述了容器苗病虫害防控的进展,提出了我国相关树种容器苗生产的启示与借鉴。     

F·Scott菲茨杰拉德与其经典短篇小说之美国梦研究

F· Scott 菲茨杰拉德对美国梦的探讨突出地表现在其长篇又系统地反映在其短篇.美国梦的实现,理论上标志着精神财富与物质财富并驾齐驱.由此产生的神秘色彩使人们对它向往已久,进而夸大其在社会发展过程中的动力作用.通过大量阅读和详尽分析,揭示出美国梦在菲小说中自起源至破灭的各个阶段,力图在肯定其积极作用的同时认识其具有西方文化特点的实质.     

适应山区发展的美国布朗李的引种栽培

美国布郎李的两个品种－紫琥珀和黑宝石从１９９２年引入金华以来，表现出来的丰产稳产状，适应性强，品质佳等特点深当地群众喜爱，概述了这两个品种的生态生产物学特性及引种几个来的生长结果状况后，进而对它们的引种栽培技术作了介绍。     

美国黑莓的主要品种与栽培技术

本文重点介绍美国黑莓的主要栽培品种、栽培及加工利用技术并探讨黑莓的市场前景以指导我国黑莓的引种栽培。     

美国黑核桃实生苗、嫁接苗培育技术

美国黑核桃繁育与推广,关键在于优质苗木的培育。研究掌握黑核桃实生苗和嫁接苗的培育技术,能极大地提高苗木质量和生产效率,降低生产成本。实生苗培育方法和方块芽接技术的研究与具体应用,为黑核桃优质苗木的生产及黑核桃在甘肃省的普遍推广创出了一条行之有效的途径。     

Changes in root growth and relationships between plant organs and root hydraulic traits in American elm (Ulmus americana L.) and red oak (Quercus rubra L.) seedlings due to elevated CO2 level

The relationships between plant organs and root hydrological traits are not well known and the question arises whether elevated CO2 changes these relationships. This study attempted to answer this question. A pseudo-replicated experiment was conducted with two times 24 American elm (Ulmus americana L.) and 23 and 24 red oak (Quercus rubra L.) seedlings growing in ambient CO2 (around 360 μmol·L–1) and 540 ± 7.95 μmol·L–1 CO₂ in a greenhouse. After 71 days of treatment for American elm and 77 days for red oak, 14 American elm and 12 red oak seedlings from each of the two CO2 levels were randomly selected in order to examine the flow rate of root xylem sap, root hydraulic conductance, total root hydraulic conductivity, fine root and coarse root hydraulic conductivity. All seedlings were harvested to investigate total plant biomass, stem biomass and leaf biomass, leaf area, height, basal diameter, total root biomass, coarse root biomass and fine root biomass. The following conclusions are reached: 1) plant organs respond to the elevated CO2 level earlier than hydraulic traits of roots and may gradually lead to changes in hydraulic traits; 2) plant organs have different relationships with hydraulic traits of roots and elevated CO2 changes these relationships; the changes may be of importance for plants as means to acclimatize to changing environments; 3) biomass of coarse roots increased rather more than that of fine roots; 4) Lorentzian and Caussian models are better in estimating the biomass of seedlings than single-variable models.     

鹅掌楸属树种种源试验研究

以木兰科鹅掌楸属的2个种，即中国鹅掌楸和北美鹅掌楸的17个种源试验林为材料，分析了各种源12a生时的生长量。结果表明：生长量在两个种间差异明显，北美鹅掌楸明显优于中国鹅掌楸；同时，生长量在种内不同种源间也存在显著差异，而种源内个体间差异不显著。对中国鹅掌楸12个种源的生长量与地理、气候因子的相关分析结果表明中国鹅掌楸的生长量有从南至北逐渐增加的趋势，呈现出渐变群的地理变异模式；而生长量与气候因子相关不大。通过聚类分析，可将中国鹅掌楸12个种源分为两大类。     

Integrating traditional and local ecological knowledge into forest biodiversity conservation in the Pacific Northwest

The potential for traditional and local ecological knowledge to contribute to biodiversity conservation has been widely recognized, but the actual application of this knowledge to biodiversity conservation is not easy. This paper synthesizes literature about traditional and local ecological knowledge and forest management in the Pacific Northwest to evaluate what is needed to accomplish this goal. We address three topics: (1) views and values people have relating to biodiversity; (2) the resource use and management practices of local forest users, and their effects on biodiversity; (3) models for integrating traditional and local ecological knowledge into biodiversity conservation on public and private lands. We focus on the ecological knowledge of forest users belonging to three groups who inhabit the region: American Indians, family forest owners, and commercial nontimber forest product harvesters.