Treesearch

Models of habitat selection commonly asume that higher-quality source habitats will be occupied at higher densities than sink habitats. We examined an apparent sink habitat for California Towhees (Pipilo crissalis) in which densities are greater than in nearby source habitats. We estimated territory density using spot-mapping and monitored nests of towhees in grazed and ungrazed oak-pine woodland habitat. Breeding density of California Towhees was higher in ungrazed oak-pine woodlands than in grazed areas, yet birds in the ungrazed site experienced lower reproductive success. Predation...

As forested watersheds become more intensively managed, it is increaseingly important to understand the range of hydrologic impacts in order to maintain the biodiversity and sustainability of these forested systems. Paired-watershed studies are often used to evaluate effects of timber harvest on watershed processes.

Streamflow in a rain-dominated, 473-ha watershed bearing second-growth redwood forest was monitored at 13 locations before and after 50% of the watershed was logged, primarily by clearcutting. Three gauged subwatersheds were maintained as unlogged controls through-out the 11-year study period. The analysis included 526 observations of peak flow from 59 storm events.

Abstract - A one-dimensional, finite difference model of saturated subsurface flow within a hillslope was developed. The model uses rainfall, elevation data, a hydraulic conductivity, and a storage coefficient to predict the saturated thickness in time and space. The model was tested against piezometric data collected in a swale located in the headwaters of the North Fork Caspar Creek Experimental Watershed near Fort Bragg, California. The model was limited in its ability to reproduce historical piezometric responses.

Abstract - The presence of small steelhead (Oncorhynchus mykiss; averaging 55 mm fork length) influenced the growth of larger juvenile steelhead (90 mm fork length) during a 6-week experiment conducted in North Fork Caspar Creek, California, in summer 1994. In fenced replicate deep stream sections in this small stream, growth of the larger steelhead was greater in treatments in which small steelhead constituted half of the total biomass of fish than in treatments with an equal biomass comprised entirely of larger fish. In shallow habitats, growth of larger fish was lower in the presence of...

Data supporting reductions in cooling load and related demand for electric power possible from increasing building surface albedo are limited. Electrical use of wall-mounted air conditioners, roof temperatures, and related environmental factors were monitored during the summer of 1990 on three initially identical 1/4-scale model buildings situated in rock mulch landscapes in Tucson, Arizona. Model thermodynamic properties were scaled to approximate thermodynamic similarity with full-size buildings. With ceiling insulation of Rvalue 5.28 m2K W−1(R-30) installed, increasing roof albedo of...

Taxodium distichum var.distichum) subjected to flooding with saline water were evaluated in this study. Ten of the families were from coastal sites in Louisiana and Alabama, USA that have elevated levels of soil-water salinity. The other five families were from inland, freshwater sites in Louisiana. Seedlings from all families tolerated flooding with water of low (2 g 1−1) salinity. Differences in biomass among families became most apparent at the highest salinity levels (6 and 8 g 1−1). Overall, increasing salinity reduced leaf biomass more than root biomass, which in turn was reduced...