Treesearch

Garry oak or Oregon white oak (Quercus garryana) is the dominant vegetation on the Whetstone Savanna in Jackson County, Oregon. The site is located on the western edge of the Agate Desert, an alluvial fan capped with shallow clay loam over a cemented hardpan. The landform exhibits patterned ground with mounds and vernal pools. The oaks are associated with buck brush (Ceanothus cuneatus) and with native and exotic grasses. In preparation for a study of the biocomplexity of common mycorrhizal networks among oaks and grasses, we examined the mycorrhizal morphotypes on Garry oak. We sampled...

Spring-fed wetlands are small, highly productive, patchy ecosystems nested within the oak woodland/annual grassland matrix of the Sierra Nevada foothills. In an effort to place these wetlands in a landscape context, we described seasonal variation (1999-2000 growing season) in nitrogen cycling parameters at 6 spring-fed wetland sites of the Sierra Nevada foothill oak woodlands. Ammonium and nitrate pool sizes covaried inversely with nitrate dominance (about 3 μg N g dry soil-1) in autumn/winter during plant dormancy and ammonium dominance (about 6 μg N gds-1) in spring/summer when wetland...

The objectives of this study were to compare soil-surface bulk density between rangeland pastures not grazed since 1935, 1975, and 1995 to grazed areas with a 15-year record of light (>1,000 lbs ac-1 RDM), moderate (600-800 lbs ac-1 RDM), and heavy (

As human and natural forces continue to alter the hardwood landscape, resource agencies, county planners and local interest groups find it increasingly important to monitor and assess these alterations. The California Land Cover Mapping and Monitoring Program (LCMMP), a cooperative program between the USDA Forest Service and the California Department of Forestry and Fire Protection, is addressing statewide long-term monitoring strategies using Landsat Thematic Mapper (TM) satellite imagery. The LCMMP creates seamless vegetation and monitoring data across California's landscape for regional...

The widening use of sediment surrogate measurements such as turbidity necessitates consideration of new methods for estimating sediment flux. Generally, existing methods can be simply be used in new ways. The effectiveness of a method varies according to the quality of the surrogate data and its relation to suspended sediment concentration (SSC). For this discussion, it is assumed that for each estimated period the surrogate data are accompanied by corresponding SSC data. If they are not, then the suspended sediment flux (i.e. yield or load) estimates are likely to be very poor. The...

Abstract - Estimates of erosion and sediment delivery have often relied on measurements from locations that were selected to be representative of particular terrain types. Such judgement samples are likely to overestimate or underestimate the mean of the quantity of interest. Probability sampling can eliminate the bias due to sample selection, and it permits the explicit expression of uncertainty with estimates of variance and confidence intervals. In this case study of the Van Duzen River Basin of northwestern California,erosion and sediment delivery originating after 1955 were estimated...

Abstract - Motivated by a particular interest in the distribution of the nonindigenous, piscivorous Sacramento pikeminnow, Ptychocheilus grandis, we examined fish-habitat relationships in small tributaries (draining 20-200 km 2 )in the Eel River drainage of northwestern California.We sampled juvenile and adult fish in 15 tributaries in both the summer and fall of 1995 and attempted to relate the densities of the most abundant species to physical variables. To determine which species used small tributaries for spawning,we also collected drifting larval fish during the spring of 1996 and 1997.

Social trust, the willingness to rely on those with formal responsibility to develop policies and make decisions, facilitates effective management of environmental issues, including wildlife management. National polls suggest that the public trusts government agencies to solve environmental problems, yet such trust is low (or non-existent) in areas of controversy, such as the protection of threatened and endangered species. This study explored the role of social trust in understanding views of threatened and endangered species management in the National Forests of southern California. The...

Dead trees, both snags (standing dead trees) and logs (downed dead trees), are critical elements of healthy and productive forests. The “Symposium on the Ecology and Management of Dead Wood in Western Forests” was convened to bring together forest researchers and managers to share the current state of knowledge relative to the values and interactions of dead wood to and in a functioning forest. Topics covered include the value of dead wood organisms in both terrestrial and aquatic habitats, the dynamics of dead wood, and ecological, industrial, and State and Federal land management agency...