Treesearch

Mountain yellow-legged frogs (Rana muscosa) at high elevations of the Sierra Nevada must obtain enough food during summer to survive 7–9 winter months when their aquatic habitats are frozen and food is presumably unavailable. Adults of R. muscosa prey on a variety of organisms, including aquatic and terrestrial invertebrates and anuran larvae. To determine if anuran larvae influence the condition, distribution, and survival of adults of R. muscosa, we assessed body condition (variation from the expected mass for given length) and distribution of R. muscosa in relation to abundance and...

Throughout their geographic distribution, American martens (Martes americana) are closely associated with late-successional mesic coniferous forests having complex physical structure at or near the ground (Bissonette et al. 1989, Buskirk and Ruggiero 1994). Recently, Zielinski et al. (2000b) documented a substantial decline in the distribution of a recognized subspecies, M. a. humboldtensis, endemic to the coastal forests of northwestern California (Grinnell and Dixon 1926). Currently there is only one known population occupying less than 5% of the historical range. There have been no...

Regional amphibian distribution patterns can vary greatly depending on species and the spatial scale of inquiry (e.g., landscape to microenvironment). These differences appear to be related both to habitat selection among species as well as availability of suitable habitats across scales. We sampled amphibians in 39 second- and third-order streams in the conifer-hardwood forests of northwestern California and southwestern Oregon, USA (the Klamath-Siskiyou Region) during 1984 and 1985. We concurrently measured spatial, structural, compositional, and climatic attributes of the forest and...

Oxidant air pollution symptoms were first reported in bioindicator plants in the Mexico City Air Basin (MCAB) in 1971 (de Bauer 1972). Classic injury symptoms on well-known bioindicator plants strongly supported the presumption that symptoms were caused by photochemical oxidants, of which ozone (O3) is the primary pollutant. Symptoms in indicator plants characteristic of injury caused by peroxyacetyl nitrate (PAN), ethylene, and sulfur dioxide (SO2) were also reported (de Bauer 1972; de Bauer and Hernández-Tejeda 1986). These discoveries were followed in 1976 by the observation of O3...

Bat detectors are widely used to compare bat activity among habitats. We placed 8 Anabat II detectors at 2 heights. 3 directions and 2 angles with respect to horizontal to evaluate the effect of detector orientation on the number of bat detections received. The orientation receiving the maximum number of detections had 70% more detections than the mean of the 7 other orientation on the same night. We found that detectors on 1.4-m stands received 30% more detections than detectors placed directly on the ground. Detectors oriented toward the direction with the fewest trees received 24-44%...

The Kings River Sustainable Forest Ecosystems Project was initiated on the Kings River Ranger District of the Sierra National Forest, California, in 1993, with fieldwork beginning in 1994. Knowledge of the ecology of the fisher (Martes pennanti) in the Project area, and in the Sierra Nevada of California in general, is insufficient to develop empirically based management strategies or to respond to the challenge of sustaining viable local populations concurrent with projected human population growth in the Sierra. Using a combination of track-plate surveys, snowtrack searches, and live-trap...