Treesearch

Small mammals are important components of woodlands and forests. Since 1992, we have been studying several aspects of small mammal ecology in oak woodlands in western foothills of the southern Sierra Nevada. Assemblages of small, nocturnal mammal species are dominated by the brush mouse (Peromyscus boylii), California mouse (P. californicus), and dusky-footed woodrat (Neotoma fuscipes). Brush mice and California mice were found in highest numbers on sites with the densest vegetative cover. Populations of both species generally appeared to decline over the 4 years of study. Dusky-footed...

This study is investigating the abundance and productivity of birds breeding in four forest types over an elevational gradient in conifer forests of the southern Sierra Nevada of California to identify the most productive habitats for each species, and to examine elevational shifts in abundance, especially as they relate to temperature and precipitation. Species richness and abundance decreased with increasing elevation, although higher elevations were important for cavity-nesting species. Abundance and nest success varied across years and forest types. Dark-eyed juncos (Junco hyemalis)...

Although research on spotted owls (Strix occidentalis) has increased dramatically in the last decade, factors influencing owl reproduction still are poorly known. This ongoing study uses 9 years of demographic data to analyze associations between owl reproduction and weather, cone crop abundance, and nest-site structure. Initial results indicate no correlation between cone crop abundance and owl reproduction, but significant associations between owl reproductive success and spring weather conditions and nest-site structure.

Nine years (1990–1998) of demographic data on California spotted owls (Strix occidentalis occidentalis) in two study areas on the western slopes of the Sierra Nevada—one in the Sierra National Forest (SNF), the other in Sequoia/Kings Canyon National Parks (SNP)—are summarized. Numbers of territorial owls fluctuated from 85 to 50 in SNF and 80 to 58 in SNP over the period from 1990 to 1998, and demographic parameters indicate significantly declining populations in both study areas during the same period. Owl densities in conifer forests, reproductive performance, and survival rates did not...

Truffles are an important food source for many small mammals in forest ecosystems; however, we know little about the seasonality, abundance, or diversity of the truffle community in the Sierra Nevada. This study examined how truffle abundance and diversity varied between oak woodland, ponderosa pine (Pinus ponderosa), mixed-conifer, and red fir (Abies magnifica) forests. Species richness (number of species) and abundance of truffles were highest in ponderosa pine stands, but species evenness was greatest in mixed-conifer stands. Truffle biomass peaked in late spring and fall, tracking...

From May 1987 through October 1992 and from July through August 1998, we studied diets of California spotted owls (Strix occidentalis occidentalis). Regurgitated pellets were collected at roost and nest sites between 1,000 and 7,600 ft elevation in the Sierra National Forest and were examined for remnant bones, feathers, and insect exoskeletons. Remains of 2,038 individual prey were identified in 1,140 pellets. Woodrats (Neotoma spp.) were the predominant prey in low-elevation oak woodlands and riparian-deciduous forests, accounting for 74.3 percent of the biomass in diets during the...

Progress on two main studies on fungal ectomycorrhizal communities in the Sierra National Forest is discussed. One study examined the short-term effects of ground fire on the ectomycorrhizal community and the other examined the ectomycorrhizal associates of snow plant (Sarcodes sanguinea). In the ground-fire study we found that a large initial reduction in ectomycorrhizal biomass is caused primarily by combustion of the upper organic layers; prefire dominants in the Russulaceae and Thelephoraceae are dramatically reduced; and species at greater depths appear to survive the fire. We...

Watershed analyses and assessments for the Kings River Sustainable Forest Ecosystems Project were done on about 33,000 acres of the 45,500-acre Big Creek watershed and 32,000 acres of the 85,100-acre Dinkey Creek watershed. Following procedures developed for analysis of cumulative watershed effects (CWE) in the Pacific Northwest Region of the USDA Forest Service, the present project is comparing the Equivalent Roaded Area (ERA) method used widely in the Pacific Southwest Region of the Forest Service, a method that has several inherent weaknesses. Selected stream reaches have been described...

A critical question in the Sierra Nevada concerns how to use disturbance effectively to restore forest ecosystems after nearly a century of fire suppression. With increases in stem densities and ladder fuels, many forests require a combination of stand thinning and controlled burning to mimic natural fire intensity. In spite of their widespread use, the different effects of fire and thinning on fundamental ecological processes have never been studied in mixed-conifer forests of the Sierra Nevada. The Teakettle Ecosystem Experiment is designed to compare these effects in an old-growth,...

The prescribed fire program on the Sierra National Forest is in its infancy. Prescription burning was initiated in 1994 in two 32,000-acre watersheds in the Kings River District of the Sierra National Forest. Primary objectives are to return fire to a more historical role in forest ecosystems and to provide opportunities for scientists from the Pacific Southwest Research Station, and elsewhere to study various effects of these fires. Approximately 11,900 acres of prescription burns were completed by the end of 1999, and documents required by the National Environmental Policy Act have been...