Treesearch

Field experiments were conducted to determine whether the frequency of Ceratocystis fagacearum and Ophiostoma quercus propagule acquisition by nitidulids visiting oak wilt fungal mats is affected by the presence of O. quercus on the mats. Augmentation sprays with O. quercus were used to achieve different levels of mat colonization by that fungus. The extent of colonization by O. quercus 7 to 14 days after spraying was greatest for postmature mats with open cracks (>0.5 cm) observed on the spray date (P < 0.02). specifically, all six subsamples assayed per mat for 16 of 18 open, O. quercus-s...

We measured the photosynthetic capacity (Pmax) of plantation-grown red spruce (Picea rubens Sarg.) during two winter seasons (1993-94 and 1994-95) and monitored field photosynthesis of these trees during one winter (1993-94). We also measured Pmax for mature montane trees from January through May 1995. Changes in Pmax and field photosynthesis closely paralleled seasonal changes in outdoor air temperature. However, during thaw periods, field photosynthesis was closely correlated with multiple-day temperature regimes, whereas Pmax was closely correlated with single-day fluctuations in...

Urban vegetation can directly and indirectly affect local and regional air quality by altering the urban atmospheric environment. Trees affect local air temperature by transpiring water through their leaves, by blocking solar radiation (tree shade), which reduces radiation absorption and heat storage by various anthropogenic surfaces (e.g., buildings, roads), and by altering wind characteristics that affect air dispersion.

The destruction of natural habitats has motivated scientists and environmentalists to collect, measure, and--one hopes--ultimately preserve as much of this planet's diverse biota as possible. Simultaneously, growing human populations have impelled research into how components of this biota can be manipulated to avert a crisis in human food, shelter, and health. Increasingly, collections of germplasm furnish the material basis for applied microbiology (Jong 1997). In addition, living collections also strongly contribute to the basic sciences, including systematics. Botanical herbaria,...

As the emphasis of forest stand management shifts towards implementing ecosystem management, managers are examining alternative methods to harvesting stands in order to accomplish multiple objectives by using techniques such as shelterwood harvests, thinnings, and group selection methods, thus leaving more residual trees to improve the visual quality of the harvested land. Contemporary harvesting practices require the creative use of existing cable and ground-based technology. Silvicultural operations such as group selection methods, shelterwood harvests, partial cuts and thinnings require...

Cultural practices can be applied in even-age stands to reallocate site resources to selected crop trees. Precommercial thinning in sapling stands can increase diameter growth and improve species composition of trees in the main canopy. Commercial thinning in sawtimber stands also increases diameter growth of crop trees, improves residual stand quality, and removes trees that would die absent thinning. Silviculturists need quantitative information on the response of particular species to thinning treatments to meet specific management objectives. In this study, 7- to 80-year-old northern...

Partial cutting to develop two-age stands is a relatively new practice in the central Appalachian region, and forest managers need quantitative information in order to evaluate how well it meets management objectives. Typically, this practice leaves a residual overstory of 10 to 40 ft2 per ac of basal area and leads to regeneration of desirable shade-intolerant species which comprise the second age class. 1n this study we evaluated residual tree quality and regeneration 2 to 5 yr after cutting in 20 stands on the Monongahela National Forest in West Virginia. Tree grades were not significant...

In 1992, the National Park Service initiated a project to galvanize local interest in the conservation and use of the Chicago Waterway System. The purpose of this project was to promote local stewardship of the waterway system through the integration of economic development, recreation, and environmental conservation. As a result, the ChicagoRivers Demonstration Project was initiated to include government resource agencies and private interests. These entities included the National Park Service, the USDA Forest Service, U.S. Fish and Wildlife Service, U.S. Army Corps of Engineers, MWRDGC,...

We investigated the daily exchange of C02 between undisturbed Larix gmelinii (Rupr.) Rupr forest and the atmosphere at a remote Siberian site during July and August of 1993. Our goal was to measure and partition total C02 exchanges into aboveground and belowground components by measuring forest and understory eddy and storage fluxes and then to determine the relationships between the environmental factors and the observations of ecosystem metabolism.