Treesearch

We compared breeding avian communities among 11 habitat types in north-central Michoacan, Mexico, to determine patterns of forest use by endemic and nonendemic resident species. Point counts of birds and vegetation measurements were conducted at 124 sampling localities from May through July, in 1994 and 1995. Six native forest types sampled were pine, pine-oak, oak-pine, oak, fir, and cloud forests; three habitat types were plantations of Eucalyptus, pine, and mixed species; and the remaining two habitats were shrublands and pastures. Pastures had lower bird-species richness and abundance...

The conservation of long-distance migratory songbirds is complicated by their life-history characteristics and the spatial scales that they traverse. Events during migratory stopovers may have significant consequences in determining the population status of migratory songbirds. Using Wilson's Warbler (Wilsonia pusilla) as a focal species, we investigated effects of age and sex on stopover parameters during spring and fall migration. Variation in stopover patterns was predominantly sex related in spring and age related in fall. In spring, males appeared at study sites earlier than females,...

Migration is a fundamental aspect of avian biology and one of the most astounding phenomena in the natural world. In North America alone there are approximately 350 species of land birds that migrate seasonally. Most of these species weigh considerably less than 50 g and travel thousands of kilometers twice annually. Migratory biology has attracted and, in no small measure, frustrated generations of ornithologists. Much of the frustration can be traced to a simple source - namely, it is very difficult to study an individual migrating bird for any appreciable time or distance. Traditional...

Disturbed areas within the Grand Fir Mosaic (GFM) ecosystem of northern Idaho show little to no natural conifer regeneration. Clear-cut sites are invaded quickly by bracken fern successional communities and seem to be in an arrested state of secondary succession. This study compared the soil solution composition of Andisols supporting bracken fern successional communities with undisturbed forest to determine the effects of shifts in vegetation communities. Treatment areas included undisturbed forest, a 30-year-old bracken fern glade (clear-cut in 1965), and a natural bracken fern glade...

Increasingly, natural resource management is seeing calls for new paradigms. These calls pose challenges that have implications not only for planning and management, but also for the practice of science. As a consequence, the profession needs to deepen its understanding of the nature of science by exploring recent advances in the philosophy of science. We believe that one of the problems inhibiting a better understanding of science is a strongly ingrained belief that science is about methodology. This perspective is reflected in Hetherington, Daniel, and Brown's (1994) recent criticism of...

This study was conducted to evaluate the dynamics of endemic populations of mountain pine beetle (Dendroctonus ponderosae Hopkins). In addition, we extended the geographical range of an existing data base recorded in Utah with similar data from Wyoming. This work was accomplished in lodgepole pine (Pinus contorta Dougl. Var. latifolia Engelm.) stands on the Medicine Bow National Forest in south-central Wyoming. Thirty-eight variable-radius paired plots (BAF 10) were measured during the summer of 1987. Host-tree condition and mountain pine beetle infestation characteristics were determined...

High-elevation ecosystems in the western United States typically have patchy, discontinuous areas of surficial soils surrounded by large areas of rock outcrop, talus, and scree. Snowmelt and precipitation that percolate through soil increase in alkalinity, principally by increasing base cation concentration through cation exchange, and by decreasing acid anion concentration by adsorption or uptake of sulfate and nitrate. While it is widely believed that changes in chemistry during runoff over rock outcrop and through saprolite contribute to increases in alkalinity, there have been few...

Several error structures for weighted regression equations used for predicting volume were examined for 2 large data sets of felled and standing loblolly pine trees (Pinus taeda L.). The generally accepted model with variance of error proportional to the value of the covariate squared ( D2H = diameter squared times height or D2 = diameter squared) remains the best. Although D2H is a better covariate than D2, we found no significant difference between them when testing model accuracy for felled trees, but there were significant differences for standing trees. When we predicted the total...

An interagency project demonstrated the feasibility of integrating Federal surveys of terrestrial natural resources and offers a vision for that integration. At locations selected from forest inventory and analysis, National forest system Region 6, and national resources inventory surveys in a six-county area in Northern Oregon, experienced teams interpreted and made measurements on aerial photographs and measured on-site a range of soil, vegetation and animal attributes. The project demonstrated the feasibility of conducting a combined FIA/NFS/NRI survey at the substate level and suggests...

The continuous geomorphologic changes in the Middle Rio Grande in New Mexico have been of interest for many governmental agencies involved with the management and operation of this river system. Due to sedimentation problems along this river, highly developed plans for sediment detention and flood control have been carried out. Cochiti Dam was built as a part of these plans to control floodflows and induce degradation along the main stem.