Relative effectiveness of Scolytus scolytus,S. multistriatus and S. kirschi as vectors of Dutch elm disease

Three scolytid species consistently associated with Dutch elm disease were assessed and compared for their effectiveness as vectors of Ophiostoma ulmi. Assessments were based on the number of beetles within a sample carrying any detectable O. ulmi, the number of O. ulmi spores carried by individual beetles and the number of discrete gallery systems colonised by O. ulmi.     

Dr. Kurt Hubert,M. S., 65 Jahre!

Ohne Zusammenfassung     

珍稀濒危植物——双蕊兰

双蕊兰是兰科植物中最原始的孑遗植物,是老秃顶子独有物种,被列为国家二级保护植物.双蕊兰腐生小草本,生长期8月中旬至9月初,分布在以椴树和柞树为主的天然次生林内.文中描述了双蕊兰的形态特征、生态学和生物学特征及地理分布,并提出了保护建议.     

加拿大回应美国对其木材征收20％关税

加拿大自然资源部部长吉姆·卡尔(Jim Carr)和加拿大外交部长弗雷兰德(Chrystia Freeland)在美国商务部对美国进口某些加拿大针叶锯材产品征收20％税率之后发表了以下声明: “加拿大森林工业在全国各地维系着数十万个良好的中产阶级工作.森林工业是我们经济中最具创新精神的部门之一,开发新产品,扩大海外市场,同时确保我们的环境得到保护.”     

蒜头果种质资源及其研究利用现状

蒜头果(Malania oleifera Chun et S.Lee ex S.Lee)为中国特有的单种属极小种群稀有濒危植物,仅桂、滇少数县市有分布,其作为木本油料树种开发应用价值极高。文中对当前蒜头果的资源分布及数量、开发利用价值、育苗及造林情况和濒危原因等进行了简要的概述和分析,并从资源保存和育种的角度,提出了一些研究思路,以期为蒜头果种质资源保存和良种选育提供参考。     

Inorganic Sediment Budget for the North Inlet Salt Marsh,South Carolina,U.S.A.

Most salt marshes along the east coast of North America appear to accumulate sediment at a rate sufficient to keep pace with the rise in eustatic sea level and local subsidence. Thus, these marshes must be importing sediment from the coastal ocean and/or the adjacent estuaries. The sediment accumulating in the North Inlet salt marsh, South Carolina, is 80% inorganic, and, based on ²¹⁰Pb dating, is accreting at a rate of 0.098 g cm^–2 yr^–1, equal to a 2.7 mm yr^–1 vertical sedimentation rate. Tide gauge records show a relative sea level rise of 2.2 to 3.4 mm yr^–1, indicating this marsh is maintaining its elevation relative to mean sea level rise. The North Inlet salt marsh has two avenues of sediment exchange: (1) through the tidal inlet to the ocean and (2) through Winyah Bay, the adjoining estuary. Long-term inorganic suspended sediment flux through the inlet is calculated to be a net import of 1.35 kg s^–1, based on application of a tidal hypsometric flow model to seven years of daily suspended sediment concentrations. However, the import required to balance relative sea level rise is only 0.80 kg s^–1, implying an excess net import of 0.55 kg s^–1. The difference between import and accumulation is explained by the progradation of the marsh toward Winyah Bay, a conclusion which is supported by the geomorphology and stratigraphy of the marsh-estuary border. Thus, the North Inlet marsh imports sediment on the average through the tidal inlet, at a rate which allows for both vertical accumulation at a rate approximately equal to the relative sea level rise and also lateral expansion of the marsh.     

Disintegration of the U. S. Industrial Forest Estate: Dynamics,Trajectories, and Questions

In the past decade ownership of the corporate forestry sector in the USA has undergone remarkable transformation. Corporate consolidation, separation of processing capacity ownership from timberland ownership, and disinvestment from timberland ownership altogether have occurred rapidly and on a global scale. Vertically-integrated forest products companies, once the standard model for publically-traded corporations, have all but disappeared. A new class of timberland investors now dominates the timberland estate. These new owners can be viewed as the most recent manifestation of capital from the core seeking rent in the distant periphery. While in this respect they resemble their industrial forestry predecessors, they differ markedly with regard to landholding objectives, time horizons, management capacities and other characteristics. This transformation has created new challenges and opportunities for other forest owners and for rural communities. Many timber processing mills have closed, restricting markets for smallholder wood. While much former industrial timberland remains in industrial-style timber management, some has been subdivided for ‘highest and best use,’ and conservation buyers have assumed control of a few large blocks. Further fragmentation of the industrial forest estate is anticipated, presenting both challenges and opportunities to small-scale forest owners and rural communities. This paper outlines the dynamics of forest ownership restructuring, posits alternative future scenarios for small-scale forestry, and points to potentially useful future research.     

Spread of European mistletoe (Viscum album) in California,U.S.A.

Viscum album was introduced in about 1900 into an area north of San Francisco, California. By 1984, the gross area covered by the parasite had spread to about 114 sq. km. The average distance of spread from the point of introduction was 5.8 km. Viscum occurs on at least 22 hosts in California, the most common are Acer saccharinum, Malus sylvestris, Robinia pseudoacacia, Alnus rubra, Populus fremontii, and Salix lasiandra.     

Pathogenic variability of various isolates of Seiridium cardinale,S. cupressi and S. unicorne inoculated on selected Cupressus clones and seedlings

Comparative studies of the pathogenicity of eight isolates of three Seiridium species were carried out by stem inoculations on Cupressus sempervirens and C. glabra seedlings and clones. Seiridium cardinale and S. cupressi caused bigger and more severe cankers than all strains of S. unicorne. During the first nine months after inoculation, the canker length of S. cardinale was larger than the cankers of S. cupressi. However, during the second year after inoculation, S. cupressi cankers were larger and more severe than those of 5. cardinale.     

美国林业近况

美国森林资源丰富,不仅是当今世界林产品生产和消费大国,而且还是林产品的主要出口国,其在国际林产品市场中发挥着重要作用。美国森林特别是私有林在经营上,国家采取政策扶持、技术支持等一系列优惠政策,鼓励林业主和林业企业发展私有林。目前,从中央到地方,全国已建立了一个完善的林业管理体系,保障林业的健康发展。