Treesearch

A study of mean wind speeds and directions has been completed in the Snowy Range of Southern Wyoming, U.S.A. It was conducted in a subalpine ecosystem at an altitude of 3 200 m to 3 400 m above sea level during the summers of 1988 and 1989. Indexes of deformation and axes of asymmetry due to wind shaping of Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) are related to wind speeds and directions on a 100 m x 100 m grid spacing over the 300 ha research site. Isotach and airflow patterns are drawn to represent climatological near-ground-level winds.

Studies were conducted on 27 species of alpine plants to test the hypothesis that structural characteristics of leaves have a predictable influence on the amount of moisture retained by a plant crown following a simulated rain event. The retention of precipitation in crowns has been previously demonstrated as one factor potentially contributing to the direct effects of acid rain on alpine plants. The results of this study demonstrate that a significant share of the amount of water retained could be explained by general structural features of leaves and flowers common to all the diverse...

Proper management of the valuable data from remeasured (or permanent) forest growth plots with data base management systems (DBMS) can greatly add to their utility. Twelve desired features for such a system (activities that facilitate the storage, accuracy, and use of the data for analysis) are described and used to evaluate the 36 systems found by a survey conducted in 1988. Most of the systems hag some positive characteristics, but none fully implemented all of the desired features. Additional DBMS features, which respondents of the survey noted would be desirable, are also summarized.

In the fall of 1990, a major program for the conservation of migratory landbirds that breed in North America and winter in Latin America and the Caribbean Basin was initiated. Numerous federal, state. and private organizations in the United States endorsed the initiative by signing an official agreement to cooperatively conserve populations of neotropical migratory birds. These include the U.S. Fish and Wildlife Service, the U.S. Forest Service, Bureau of Land Management, National Park Service, Agency for International Development, Department of Defense, National Audubon Society, The...

Mas de 250 especies de aves terrestres migran a Norte America durante la epoca reproductiva para aprovechar los sistemas templados. No obstante, las aves migratorias neotropicales pasan la mayor parte de su ciclo de vida en los habitat tropicales y subtropicales de paises latinoamericanos y caribefios donde viven en una asociacion cercana con las aves residentes. Para su supervivencia, muchas especies migratorias dependen de los ecosistemas tropicales. Aunque existe informacion sobre la biologia reproductiva de las aves migratorias, hay poca informacion disponible sobre la distribucion,...

Includes 19 papers documenting presentations at the 1991 Forest Service National Silviculture Workshop. Discussions focus on the role of silviculture in New Perspectives (ecosystem management), new approaches to the practice of silviculture, and examples of successful integration of practices into multi resource management.

In addition to thematic maps, remote sensing provides estimates of area in different thematic categories. Areal estimates are frequently used for resource inventories, management planning, and assessment analyses. Misclassification causes bias in these statistical areal estimates. For example, if a small percentage of a common cover type is misclassified as a rare cover type, then the area occupied by the rare type can be severely overestimated. Many categories are rare in detailed classification systems. I present an informal method to anticipate the approximate magnitude of this bias in...

Classifications of remotely sensed data contain misclassification errors that bias areal estimates. Monte Carlo techniques were used to compare two statistical methods that correct or calibrate remotely sensed areal estimates for misclassification bias using reference data from an error matrix. The inverse calibration estimator was consistently superior to the classical estimator using a simple random sample of reference plots. The effects of sample size of reference plots, detail of the classification system, and classification accuracy on the precision of the inverse estimator are...

The 1988 Gates Park Fire, along the North Fork of the Sun River in the Bob Marshall Wilderness, provided an opportunity to explore fire effects on wilderness visitor choices. Recreation visitors along the North and South Fork drainages were interviewed to assess the effects of 1988 fires on their 1989 visits. The Gates Park fire had relatively little impact on the choice to visit the North Fork or the South Fork. Visitors placed more importance on remoteness and naturalness in selecting trails and campsites than on the effects of the fires. The fire effects apparently are not seen as an...

The overall trend in condition on established campsites was one of slight deterioration, with the most deterioration occurring in campsite area, mineral soil exposure, and tree damage. Impacts to ground cover vegetation were relatively stable. Differences in amount of impact between high-use and low-use sites generally increased over time.