Treesearch

Prescribed fire was returned into over-stocked ponderosa pine stands on the Mogollon Rim of Arizona for the purpose of restoring fire into the ecosystem and removing fuel buildups. Prescribed fires have been ignited at intervals of 1, 2, 4, 6, 8, and 10 years to determine the best fire return interval for Southwest ponderosa pine ecosystems. Two sites were treated; one on volcanic-derived soils, and the other on sedimentary-derived soils near Flagstaff, Arizona, starting in 1976 and 1977, respectively. Samples from upper 5 cm of the A horizons were analyzed for total carbon and nitrogen...

Traditional land classification techniques for large areas that use Landsat Thematic Mapper (TM) imagery are typically limited to the fixed spatial resolution of the sensors (30m). However, the study of some ecological processes requires land cover classifications at finer spatial resolutions. We model forest vegetation types on the Kaibab National Forest (KNF) in northern Arizona to a 10-m spatial resolution with field data, using topographical information and Landsat TM imagery as auxiliary variables. Vegetation types were identified by clustering the field variables total basal area and...

Between 1975 and 2000, 4,525 sightings of wintering bald eagles (Haliaeetus leucocephalus) were recorded at Mormon Lake in northern Arizona. Numbers of wintering eagles fluctuated little in the 20 years from 1975 through 1994 (5.5 ± 3.0 mean sightings per day). However, during the winters of 1995 through 1997 local record highs of 59 to 118 eagles increased mean sightings per day to 22.4 ± 9.6. This dramatic population increase led to a major change in social behavior favoring consistent communal roosting; maximum roost counts of 2 to 8 eagles scattered among 11 roosts in prior years...

Finite population sampling theory is useful in estimating total population size (abundance) from abundance estimates of each sampled unit (quadrat). We develop estimators that allow correlated quadrat abundance estimates, even for quadrats in different sampling strata. Correlated quadrat abundance estimates based on mark–recapture or distance sampling methods occur when data are pooled across quadrats to estimate, for example, capture probability parameters or sighting functions. When only minimal information is available from each quadrat, pooling of data across quadrats may be necessary...

As part of a set of studies evaluating home-range size and habitat use of radio-marked Mexican spotted owls (Strix occidentalis lucida), we sampled structural characteristics of forest stands within owl home ranges on two study areas in Arizona and New Mexico. Study areas were dominated by ponderosa pine (Pinus ponderosa)-Gambel oak (Quercus gambelii) forest (Arizona) or mixed-conifer forest (New Mexico). We describe structural characteristics of forest stands used by spotted owls for both foraging and roosting, in terms of central tendencies and variability in structural characteristics...

Autumn willow, Salix serissima (Bailey) Fern., is an obligate wetland shrub that occurs in fens and bogs in the northeastern United States and eastern Canada. Disjunct populations of autumn willow occur in the Black Hills of South Dakota. Only two populations occur on Black Hills National Forest lands: a large population at McIntosh Fen and a small population on Middle Boxelder Creek. Both populations occur in association with specific geologic and hydrologic conditions that have resulted in an elevated water table, fen-like habitats and saturated organic substrates. These habitats are...

Great-spurred violet (Viola selkirkii Pursh ex Goldie; Violaceae) is an early spring flowering herb that occurs in the boreal and Rocky Mountain regions of North America, and cool temperate regions of Eurasia, eastern China and Japan. In the Black Hills, the species is restricted to spruce-dominated forests in cold, shady ravines from 5,400 to 7,000 ft (1,645 to 2,135 m) elevation on soils derived from granitic parent material. There are currently 17 known occurrences of great-spurred violet in the Black Hills: ten on Black Hills National Forest land, including eight sites in the Black Elk...

Chemical analyses of water emanating from Fossil Springs in Central Arizona were conducted to predict changes in travertine deposition related to changes in stream discharge caused by diversion for hydroelectric power generation. During spring of 1996, water was sampled at 15 locations during normal seepage flow in a 6.7 km reach below Fossil Springs and at full baseflow during turbine maintenance. Analyses resulted in a rate of 11,923 kg d-1 of CaCO3 precipitated from 1218 l s-1 of water emanating from the springs, while flows of 5.61 s-1 that seep past a diversion dam produced 46 kg d-1...

The management of natural fire and fuels in wilderness areas of the United States presents a significant dilemma to federal land managers.Wilderness fire management requires balancing mandates to both preserve natural conditions and minimize the impacts of human activities.It also requires consideration of ecological and social values both within and outside of wilderness. In many wilderness and similarlyprotected areas, decades of fire exclusion have resulted in conditions of unnatural vegetation and fuel accumulation. Resulting fires areincreasingly of sizes and intensities unprecedented...

Fire is a natural grassland disturbance that affects a variety of ecosystem factors including nutrient cycling, species diversity, and population and community dynamics. Caution is warranted when interpreting the effects of fire on grasslands due to the variety of fire types (e.g. wildfire vs prescribed burn), season of occurrence, weather conditions, grassland uses (e.g. grazing), fire history, and fuel conditions in which a burn can occur. The length of time between fire and post-fire data collection (e.g. months vs years) will also greatly influence perceptions about fire effects (Ford...