Treesearch

Surface ozone (O3) was measured at the Devils Postpile National Monument (DEPO), eastern Sierra Nevada Mountains, California, during the 2007 (low-fire) and 2008 (high-fire) summer seasons. While mean and median values of O3 concentrations for the 2007 and 2008 summer seasons were similar, maximum O3 concentrations in June and August 2008 were higher than in any month of the 2007 summer season. This increase of maximum concentrations in the high-fire year is attributed to emissions of O3 precursors from wildland fires upwind of DEPO in addition to transport of polluted air from the...

The advent of GPS technology has made it possible to study human-wildlife interactions on large landscapes and quantify behavioral responses to recreation and other anthropogenic disturbances at increasingly fine scales. Of particular interest are the potential impacts on habitat use patterns, energetics, and cascading impacts on fecundity and other life history traits for key wildlife species that are exposed to human activities. Statistical models quantifying effects of human activity on animal movement on a heterogeneous landscape are essential for understanding these potential impacts....

This study integrates two existing computer programs, the Pest Vulnerability Matrix and i-Tree Streets, into a decision-support tool for assessing municipal forest stability and recommending strategies to mitigate risk of loss. A report card concept was developed to communicate levels of performance in terms that managers and the public easily understand. Grades were assigned to four aspects of a stable and resilient municipal forest: Species Dominance, Age Structure, Pest Threat and Potential Asset Loss. The data pool of 29 California municipal forest inventories contained information on...

Despite the abundance of rock glaciers in the Sierra Nevada of California, USA, few efforts have been made to measure their surface flow. Here we use the interferometric synthetic aperture radar (InSAR) technique to compile a~benchmark inventory describing the kinematic state of 59 active rock glaciers in this region. Statistically, these rock glaciers moved at speeds range from 15 cm yr-1 to 88 cm yr-1 with a mean value of 55 cm yr-1 in the late summer of 2007. We also find a spatial gradient: rock glaciers in the southern Sierra Nevada moved faster than the ones in the central Sierra...

To explore thermal regimes and hydrologic capacity of rock glaciers and related periglacial talus landforms, mini-thermochrons were deployed in and around potentially ice-embedded features of the Sierra Nevada. Results from pilot studies at 13 rock glaciers and 7 taluses indicate that outlet springs from these landforms generally do not desiccate but persist year-round as ice (frozen) in winter and flowing water in the warm season. Temperatures of water (liquid and ice) in rock-glacier outlet springs had an annual mean of -0.2 °C and mean of 0.6 °C during the warm season with very low...

Estimates of survival of nearctic-neotropic migrants have broadened our understanding of life-history variation across taxa and latitudes. Despite the importance of assessing migrants' survival through all phases of their life-cycle, data from their tropical winter ranges are few. In this study we used 14 years of data on captured birds to quantify the influence of mass on the annual survival of the Prothonotary Warbler (Protonotaria citrea) in northeastern Costa Rica and compared our results to survival estimates generated from the breeding grounds. Furthermore, from estimates of populatio...

Carnivores are important elements of biodiversity, not only because of their role in transferring energy and nutrients, but also because they influence the structure of the communities where they occur. The fisher Martes pennanti is amammalian carnivore that is associated with late-successional mixed forests in the Sierra Nevada in California, and is vulnerable to the effects of forest management. As a candidate for endangered species status, it is important to monitor its population to determine whether actions to conserve it are successful. We implemented a monitoring program to estimate...

A shout of gold, the groan of oxen, the whoosh of lumber down a flume, the shriek of a locomotive whistle, the laughter of children, and the distress of unemployment— all portray the people and their activities in and around Challenge Mills, a small lumber-mill town in the foothills of the northern Sierra Nevada. This report is about the people of Challenge Mills and their way of life around the turn of the 20th century. Native Americans and Chinese are included among its residents. All are inextricably linked to one dynamic individual, Andrew Martin Leach, whose strong business acumen,...

In this paper we explore whether the enhancement of urban ecosystem services through large-scale, metropolitan tree-planting initiatives is being planned and executed as a component of traditional municipal government or represents new, transdisciplinary strategies in environmental governance. Drawing on qualitative interviews with stakeholders in six major cities (n = 58) we further explore institutionalization of these initiatives and relationships. While much current discourse posits government cannot "go it alone" in providing preventative, "front&...

Many ecologists believe that there is a lack of foraging theory that works in community contexts, for populations of unique individuals each making trade-offs between food and risk that are subject to feedbacks from behavior of others. Such theory is necessary to reproduce the trait-mediated trophic interactions now recognized as widespread and strong. Game theory can address feedbacks but does not provide foraging theory for unique individuals in variable environments. ‘State and prediction-based theory’ (SPT) is a new approach that combines existing trade-off methods with routine...