Treesearch

On eastern hemlock, we found two resident beetles preying on Adelges tsugae Annand. One is a coccinellid native to Europe, Scymnus suturalis Thunberg, that also feeds on Pineus sp. that attack pines. The other is a native derodontid beetle, Laricobius rubidus LeConte. The seasonal life history of these two species indicates that their effect on A. tsugae will be more complementary than competitive. The effectiveness of these species may be enhanced by the presence of alternative prey that attack other conifers. Among the many species imported for control of the balsam woolly adelgid, the...

Scymnus (Pullus) suturalis Thunberg is a Palearctic species that occurs on conifers, where it is reported to feed on aphids (I. Hodek. 1973. Biology of Coccinellidae. Academia, Czechoslovak Academy of Science. Prague). The occurrence of S. suturalis in North America was first reported by R.D. Gordon (1982. Proc. Entomol. Soc. Wash. 84:250-25 5) who distinguished specimens collected in New York and Pennsylvania from a similar western species, Scymnus (Pullus) coniferarum Crotch.

Stylet bundle insertion site, path traveled, and feeding site were examined for the hemlock woolly adelgid, Adelges tsugae Annand, on needles from current and previous years of eastern hemlock, Tsuga canadensis Carriere. The stylet bundle is composed of 4 individual stylets--2 outer mandibular stylets and 2 inner maxillary stylets. A. tsugae inserts its stylet bundle on the adaxial side of eastern hemlock needles, proximal to the twig with respect to the leaf abscission layer. Insertions are primarily intracellular through epidermal cells. Once inserted, the stylet bundle then follows a...

Measurement of tree seedlings and herbaceous vegetation from 499 sample locations across Pennsylvania revealed that advance tree-seedling regeneration is inadequate for new stand establishment across most of the State. The samples were located in stands from 40% to 75% stocked to focus on stands with ample light and growing space for establishment of abundant advance regeneration. A range of regeneration adequacy criteria was applied to the measurements. Using the least stringent criterion, a low density of stems of any tree species, resulted in 40% of the sample locations being adequately...

Procedures developed to assess available timber supplies from upland hardwood forest statistics reported by the USDA Forest Services' Forest Inventory and Analysis unit were modified to assess the feasibility and profitability of cable logging in southern upland hardwood forests. Depending on the harvest system and yarding distance used, cable logging can be profitable in as much as 14% of the area of upland hardwood forests on slopes that are 30% or greater. These slopes contain up to one-quarter of the board-foot volume in the 14-state area that was considered. The majority of the...

The purpose of this study was to determine the most important nonanthropogenic factors affecting understory (herbs, shrubs and low-growing vines) diversity in forested landscapes of southern Indiana. Fourteen environmental variables were measured for 46 sites. Multiple regression analysis showed significant positive correlation between understory diversity and tree seedling diversity and soil subgroup. Slope aspect, soil rooting depth and number of standing dead trees were significantly negatively correlated with understory diversity. Mesic sites were more diverse in common understory...

Global concern about increasing atmospheric concentrations of greenhouse gases, particularly carbon dioxide (CO2), and the possible consequences of future climate changes, has generated interest in understanding and quantifying the role of terrestrial ecosystems in the global carbon cycle. Recent efforts to quantify the global carbon budget have revealed an unknown carbon sink of 2.0-3.4 billion metric tons/yr, of which some may be accounted for by changes in northern temperate forests (Tans et al. 1990).

The formation of whole plants from cultured cells is interesting not only because of its applications for mass propagation but also as a prime example of the process of controlled development and differentiation in plants. Cultures capable of producing somatic embryos with high frequency provide ideal experimental systems to study and understand the biochemical basis of hormonal regulation of the developmental process. This knowledge should lead to the planning of media and various treatments that allow us to obtain whole plants from single cells in recalcitrant plant species.

During the next few decades, the world demand for wood products is expected to rise sharply. To meet this growing demand, there will be an increasing need for mass production of improved-quality planting stock of many tree species. The conventional methods of tree improvement and selection offer only limited possibility of meeting the growing demands. Therefore, new and innovative techniques for the creation of new hybrids, early selection and testing of desirable genotypes, rapid vegetative propagation of selected genotypes, and improvement through genetic engineering, etc., must be...

The aliphatic amines putrescine, spermidine, and spermine are present in all living organisms. Since the demonstration of "an essential nutritional function" for putrescine in the bacterium Hemophilus parainfluenzae (Herbst and Snell 1948), polyamines have attracted a great deal of attention from workers in diverse fields of the life sciences. The first reports of the existence of putrescine in plants date back to 1911 (see Smith 1991 for a historical summary).