Treesearch

The greenback cutthroat trout (Oncorhynchus clarki stomias) is native to the mountain and foothill waters of the South Platte and Arkansas river basins in Colorado. This taxon declined rapidly beginning near the turn of the century and was listed under the Endangered Species Act in 1973. We assembled all available information from a variety of sources to document recovery efforts from 1957 to 1999. For each greenback cutthroat trout population, we noted (1) the characteristics of recovery waters and dates of population discovery or introduction; (2) fish abundance estimates; (3) analyses...

The mistletoes are a diverse group in the order Santales of shrubby, usually aerial, parasitic plants with fruits possessing a viscid layer (Kuijt 1968, 1969a). They are widely distributed geographically and as a group have a broad host range on conifers and other woody plants (Calder 1983). Many mistletoes are specially adapted for avian pollination and dispersal, and several avian species make extensive use of these resources (Kuijt 1969a, Watson 2001). The mistletoes are damaging pathogens of trees; and in many parts of the world are serious forest pests (Hawksworth 1983, Knutson 1983)....

We produced seven coarse-scale, 1-km2 resolution, spatial data layers for the conterminous United States to support national-level fire planning and risk assessments. Four of these layers were developed to evaluate ecological conditions and risk to ecosystem components: Potential Natural Vegetation Groups, a layer of climax vegetation types representing site characteristics such as soils, climate, and topography; Current Cover Type, a layer of current vegetation types; Historical Natural Fire Regimes, a layer of fire frequency and severity; and Fire Regime Current Condition Class, a layer...

We used regression quantiles to model potentially limiting relationships between the standing crop of cutthroat trout Oncorhynchus clarki and measures of stream channel morphology. Regression quantile models indicated that variation in fish density was inversely related to the width:depth ratio of streams but not to stream width or depth alone. The spatial and temporal stability of model predictions were examined across years and streams, respectively. Variation in fish density with width:depth ratio (10th–90th regression quantiles) modeled for streams sampled in 1993–1997 predicted the...

The channel head represents an important transition point from hillslope to fluvial processes. There is a nonlinear threshold transition across the channel head with sediment transport much larger in channels than on hillslopes. Deterministic specific catchment area, a, thresholds for channel initiation, sometimes dependent on slope, S, in the form of aSα ≥ C, have been suggested. In this paper the channel initiation problem is viewed probabilistically with a spatially variable probability of channel initiation that depends on slope, specific catchment area, and the probability distribution...

Large-bodied, migratory life history forms of bull charr, Salvelinus confluentus, were historically abundant in northwestern North America, but many remaining populations of this now-threatened species presently persist as small-bodied residents isolated in headwater streams.We examined whether the migratory form has been lost from headwater populations of bull charr and their potential for re-establishment. Upstream and downstream movement of bull charr and other salmonids from three tributary populations in the Bitterroot River drainage, Montana, was measured with weirs over a 17-month...

Many anadromous salmonid stocks in the Pacific Northwest are at their lowest recorded levels, which has raised questions regarding their long-term persistence under current conditions. There are a number of factors, such as freshwater spawning and rearing habitat, that could potentially influence their numbers. Therefore, we used the latest advances in information-theoretic methods in a two-stage modeling process to investigate relationships between landscape-level habitat attributes and maximum recruitment of 25 index stocks of chinook salmon (Onocorhynchus tshawytscha) in the Columbia...

We examined the use of snag stands by seven species of cavity-nesting birds from 1994-1998. Selection of snags was studied in logged and unlogged burned forests at two spatial scales: microhabitat (local vegetation characteristics) and landscape (composition and patterning of surrounding vegetation types). We modeled nest occurrence at the landscape scale by using Landsat Thematic Mapper imagery. At both spatial scales, we observed a continuum in habitat use with the extremes represented by black-backed and Lewis’s woodpeckers. A range of habitat conditions characteristic of black-backed...

The Western Division of the American Fisheries Society was requested to develop protocols for determining presence/absence and potential habitat suitability for bull trout. The general approach adopted is similar to the process for the marbled murrelet, whereby interim guidelines are initially used, and the protocols are subsequently refined as data are collected. Current data were considered inadequate to precisely identify suitable habitat but could be useful in stratifying sampling units for presence/absence surveys. The presence/absence protocol builds on previous approaches (Hillman...

The role of the Policy Analysis Center for Western Public Lands is to provide integrated social, economic and ecological analyses of public land policies that affect communities in the West. Its mission is to help rural communities, policy makers, resource managers, resource users and others understand, analyze and engage effectively in the public-land policy process. Our general objective is to identify a set of short-run (three to five years) policy alternatives that are based on a synthesis of empirical research into the needs of the greater sage-grouse (Centrocercus urophasianus) and...