Treesearch

Includes color photos of 44 species of fishes, many published for the first time. Text describes aquatic systems in the mountains and deserts of the Southwest, the unique fishes they support, and habitats the fishes need.

Models were developed to describe genetic variation among 201 seedling populations of Pinus ponderosa var. ponderosa in the Inland Northwest of the United States. Common-garden studies provided three variables Jhat reflected growth and development in field environments and three principal components of six variables that reflected patterns of shoot elongation. Regression models were developed for describing genetic variation across the landscape. Using functions of latitude, longitude, and elevation as descriptors, these models produced values of R2 that were as large as 0.66, while...

Numbers of suckers produced following burning of aspen stands varied greatly between areas but followed similar trends over a 6-year period: a relative abundance the first year, followed by an abrupt decline by the third year and a gradual decline thereafter. First-year sucker numbers that ranged from 34,000 to 147,000/ha suffered mortality between 54 and 93 percent by the sixth year. Only 40 percent of the variability between sites in number of suckers the second postburn year, and only 44 percent of the variability the sixth year, could be accounted for by season of burn and preburn site...

Our objective was to model the radial growth response of individual ponderosa pines to prescribed burning in northern Arizona. We sampled 188 trees from two study areas, which were burned in 1976. Within each study area, control and burned trees were of similar age, vigor, height, and competition index. At Chimney Spring, trees were older, less vigorous, and taller and had a higher competition index than at Brannigan. For each tree, periodic basal area increment (PBA1) was calculated for the years 1974-1984. To determine which variable would best model growth, post-fire growth (1977-1984)...

I examined timing of reproduction and productivity in box-nesting House Wrens (Troglodytes aedon) inhabiting three riverbank woodlands subjected to different levels of flooding. In years when the North Platte River flooded its banks submerging ground foraging substrates, dates of nest initiation and egg laying in two wren populations were delayed and nonsynchronized. In contrast, timing of breeding was unrelated to annual variations in water levels or spring weather in wrens occupying a riparian area buffered from flooding. Rates of nest predation were unlikely to influence timing of...

Bird count data were used to characterize patterns of abundance and distribution among 20 bird species occupying streamside habitats of the central Rocky Mountains. Cluster analysis classified bird assemblages from 10 study plots into three elevational zones that varied in bird species diversity. Monotonic declines in total bird densities over the elevational gradient corresponded to spatial fluctuations in population levels of a few numerically dominant species. Of 190 correlations in counts of species pairs, 48 were significant, a much greater proportion than that expected by chance....

The regeneration period is a crucial time in the life of a stand because it determines species composition and tree density for the new stand. Silviculturists prescribe treatments to favor adequate and timely conifer regeneration of economically important species that grow well. This paper presents research results that will help silviculturists identify factors favoring natural regeneration of interior Douglas-fir. The data were obtained from retrospective examination of randomly chosen, conventionally harvested stands 3-20 years old in Idaho and Montana. The information covers the...

The Food and Agricultural Organization (FAO) of the United Nations is conducting a global assessment of tropical forest resources, which will be accomplished by mid-1992. This assessment requires, in part, estimates of the total area of tropical forest cover in 1990, and the rate of change in forest cover between 1980 and 1990. This paper describes: (1) the strategic process used to select the statistical and remote sensing methods that accomplish this objective, (2) general details and expected precision of the selected method, and (3) recommendations for monitoring and assessment actions...

This report describes the current status of 67 threatened, endangered, and vulnerable wildlife species in the Rocky Mountain Region of the U.S. Forest Service. Known or potential reasons for population declines and species susceptibility are identified; and distributions, habitats, specialized needs, and perceived threats of individual species are discusses.

This report was prepared in support of the National Fish and Wildlife Foundation's Neotropical Migratory Bird Conservation Program and the USDA Forest Service's role in the program. Recent analyses of data on forest-dwelling species, many of which are neotropical migrants, show population declines in many North American areas. The literature review summarizes current information on population trends of neotropical migratory birds and the factors affecting migrant populations on the breeding and wintering grounds. Opportunities for research, monitoring, and conservation of these migrants on...