Treesearch

Soil respiration is a major pathway for carbon cycling in terrestrial ecosystems yet little is known about its response to natural and anthropogenic disturbances. This study examined soil respiration response to prescribed burning and thinning treatments in an old-growth, mixed-conifer forest on the western slope of the Sierra Nevada Mountains. Experimental treatments were applied in 2001 using a full factorial design consisting of two levels of burning and three levels of thinning, and included: unburned-unthinned (UN), unburned-overstory thinned (US), unburned-understory thinned (UC),...

Oak-dependent birds are expected to suffer severe population declines as a result of sudden oak death (SOD). We investigated how the disappearance of two highly SOD-sensitive tree species, tanoak (Lithocarpus densiflorus) and coast live oak (Quercus agrifolia), may in turn affect levels of bird species richness, diversity, and equitability in coastal oak habitats of California. Combining avian census data from Audubon Christmas Bird Counts and North American Breeding Bird Surveys with oak distributional data from the California Gap Analysis, we use the statistical relationships between...

Forest soil acidification and depletion of nutrient cations have been reported for several forested regions in North America, predominantly in the eastern United States, including the northeast and in the central Appalachians, but also in parts of southeastern Canada and the southern U.S. Continuing regional inputs of nitrogen and sulfur are of concern because of leaching of base cations, increased availability of soil Al, and the accumulation and ultimate transmission of acidity from forest soils to streams. Losses of calcium from forest soils and forested watersheds have now been...

The nutrient status of forest soils in the Mexico City Air Basin was evaluated by observing plant growth responses to fertilization with N, P or both nutrients combined. P deficiency was the most frequent condition for soil from two high pollution sites and N deficiency was greatest at a low N deposition site. Concentrations of Pb and Ni, and to a lesser extent Zn and Co, were higher at the high pollution sites. However, positive plant growth responses to P and sometimes to N, and results of wheat root elongation bioassays, suggest that heavy metal concentrations were not directly phytotoxi...

Fire is a critical ecosystem process in many landscapes and is particularly dominant in the chaparral shrublands of southern California which are also exposed to high levels of atmospheric N deposition. Few studies have addressed the combined effects of these two disturbance factors. In this study we evaluate the hydrologic and biogeochemical response of a control and a prescribed burn catchment over a 15-year period. Streamwater nitrate concentrations and export in the burned catchment were higher than those in the unburned catchment for 7-10 years after the burn and concentrations...

Ecosystem services is a term used to describe the benefits to people fiom natural areas (Millennium Ecosystem Assessment, 2005). Services to humans can range from food production to water purification to aesthetics. The Millennium Ecosystem Assessment (MEA) was initiated in 2001 to assess the consequences of ecosystem change for human well-being and the scientific basis for actions needed to enhance the conservation and sustainable use of those systems. The assessment involved more than 1,300 experts worldwide.

This paper reports results fiom the first in a series of studies evaluating perceptions of law enforcement officers (LEOs) in the US Forest Service (USFS). It is a follow-up to previous qualitative studies conducted to learn more about crime and violence in national forests and the impacts on recreation visitation and management, and test key characteristics of success in law enforcement, measure opinions about recreation visitor and public safety, and evaluate impacts to natural resources. Another incentive for conducting this study was to respond to a federal initiative for performance...

The fisher (Martes pennanti) is a forest-dwelling carnivore whose current distribution and association with late-seral forest conditions make it vulnerable to stand-altering human activities or natural disturbances. Fishers select a variety of structures for daily resting bouts. These habitat elements, together with foraging and reproductive (denning) habitat, constitute the habitat requirements of fishers. We develop a model capable of predicting the suitability of fisher resting habitat using standard forest vegetation inventory data. The inventory data were derived from Forest Inventory...

Recent studies have shown that Warbling Vireos (Vireo gilvus) are declining in California and that these trends are due to low reproductive success. Brood parasitism by Brown-headed Cowbirds (Molothrus ater) has been implicated in the low productivity. I explored two hypotheses related to population dynamics of Warbling Vireos along an elevational gradient: (1) potential source populations exist at high elevations where cowbirds are rare, and (2) potential source populations occur in the center of the elevational distribution with less productive populations at upper and lower elevations....

The Klamath-Siskiyou forests of northern California and southern Oregon are recognized as an area of globally outstanding biological distinctiveness. When evaluated at a national or global level, this region is often, necessarily, considered to be uniformly diverse. Due to large variation in biotic and abiotic variables throughout this region, however, it is unlikely that biological diversity is uniformly distributed. Furthermore, land management decisions nearly always occur at spatial scales smaller than this entire region. Therefore, we used field data from a random sampling design to...