Geology Reports⌕ Search

SEARCH · Geology Reports

Results for “Yosemite”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources
USGS2012

Stable isotopes to detect food-conditioned bears and to evaluate human-bear management

We used genetic and stable isotope analysis of hair from free-ranging black bears (Ursus americanus) in Yosemite National Park, California, USA to: 1) identify bears that consume human food, 2) estimate the diets of these bears, and 3) evaluate the Yosemite human–bear management program. Specifically, we analyzed the isotopic composition of hair from bears known a priori to be food-conditioned or non-food-conditioned and used these data to predict whether bears with an unknown management status were food-conditioned (FC) or non-food-conditioned (NFC). We used a stable isotope mixing model to estimate the proportional contribution of natural foods (plants and animals) versus human food in the diets of FC bears. We then used results from both analyses to evaluate proactive (population-level) and reactive (individual-level) human–bear management, and discussed new metrics to evaluate the overall human–bear management program in Yosemite. Our results indicated that 19 out of 145 (13%) unknown bears sampled from 2005 to 2007 were food-conditioned. The proportion of human food in the diets of known FC bears likely declined from 2001–2003 to 2005–2007, suggesting proactive management was successful in reducing the amount of human food available to bears. In contrast, reactive management was not successful in changing the management status of known FC bears to NFC bears, or in reducing the contribution of human food to the diets of FC bears. Nine known FC bears were recaptured on 14 occasions from 2001 to 2007; all bears were classified as FC during subsequent recaptures, and human–bear management did not reduce the amount of human food in the diets of FC bears. Based on our results, we suggest Yosemite continue implementing proactive human–bear management, reevaluate reactive management, and consider removing problem bears (those involved in repeated bear incidents) from the population.

California↗
USGS2007

Surface temperature patterns in complex terrain: Daily variations and long-term change in the central Sierra Nevada, California

A realistic description of how temperatures vary with elevation is crucial for ecosystem studies and for models of basin-scale snowmelt and spring streamflow. This paper explores surface temperature variability using temperature data from an array of 37 sensors, called the Yosemite network, which traverses both slopes of the Sierra Nevada in the vicinity of Yosemite National Park, California. These data indicate that a simple lapse rate is often a poor description of the spatial temperature structure. Rather, the spatial pattern of temperature over the Yosemite network varies considerably with synoptic conditions. Empirical orthogonal functions (EOFs) were used to identify the dominant spatial temperature patterns and how they vary in time. Temporal variations of these surface temperature patterns were correlated with large-scale weather conditions, as described by National Centers for Environmental Prediction-National Center for Atmospheric Research Reanalysis data. Regression equations were used to downscale larger-scale weather parameters, such as Reanalysis winds and pressure, to the surface temperature structure over the Yosemite network. These relationships demonstrate that strong westerly winds are associated with relatively warmer temperatures on the east slope and cooler temperatures on the west slope of the Sierra, and weaker westerly winds are associated with the opposite pattern. Reanalysis data from 1948 to 2005 indicate weakening westerlies over this time period, a trend leading to relatively cooler temperatures on the east slope over decadal timescale's. This trend also appears in long-term observations and demonstrates the need to consider topographic effects when examining long-term changes in mountain regions. Copyright 2007 by the American Geophysical Union.

Journal of Geophysical Research D: Atmospheres↗
USGS2012

Mapped versus actual burned area within wildfire perimeters: Characterizing the unburned

For decades, wildfire studies have utilized fire occurrence as the primary data source for investigating the causes and effects of wildfire on the landscape. Fire occurrence data fall primarily into two categories: ignition points and perimeter polygons which are used to calculate a ‘burned area’ for a fire. However, understanding the relationships between climate and fire or between fire and its ecological effects requires an understanding of the burn heterogeneity across the landscape and the area within fire perimeters that remains unburned. This research characterizes unburned areas within fire perimeters, which provide ecological refugia and seed source for post-fire regeneration. We utilized differenced Normalized Burn Ratio (dNBR) data to examine the frequency, extent, and spatial patterns of unburned area in three national parks across the western US (Glacier, Yosemite, and Yukon-Charley Rivers). We characterized unburned area within fire perimeters by fire size and severity, characterized distance to an unburned area across the burned portion of the fire, and investigated patch dynamics of unburned patches within the fire perimeter. From 1984 through 2009, the total area within the fire perimeters that was classified as unburned from dNBR was 37% for Yosemite, 17% for Glacier, and 14% for Yukon-Charley. Variation in unburned area between fires was highest in Yosemite and lowest in Yukon-Charley. The unburned proportion significantly decreased with increasing fire size and severity across all three parks. Unburned patch size increased with size of fire perimeter, but patches decreased in density. There were no temporal trends in unburned area found. These results raise questions about the validity of relationships found between external forcing agents, such as climate, and ‘burned area’ values derived solely from polygon fire perimeters.

Alaska, Montana, Wyoming↗
USGS1990

The late Cenozoic evolution of the Tuolumne River, central Sierra Nevada, California

Erosional remnants of volcanic rock deposited in a lO-m.y.-old channel of the Tuolumne River permit its partial reconstruction. Projection of the reconstructed channel west to the Central Valley and east to the range crest, together with several assumptions about the position of the hinge line and changes in channel gradient, allows estimates of the amount of uplift at the range crest during the past 10 m.y. At Tioga Pass, this amounts to as much as 1,830 m, as compared to the 2,150 m estimated in an earlier study for Deadman Pass at the San Joaquin River 30 km to the south. Comparison of the geometry of these river systems leads to the conclusion that 10 m.y. ago an ancestral range of hills occupied the present site of the Sierran crest, and, although of relatively moderate relief, it was a barrier to westward drainage even before late Cenozoic uplift. At that time, the San Joaquin River was apparently the only river flowing westward across the range from well south of Mount Whitney north to Sonora Pass. The Tuolumne River evidently never extended east of this range. Comparison of the ancient channel with the modern channel of the Tuolumne River permits analysis of the later evolution of the river system and the development of Hetch Hetchy Valley and the Grand Canyon of the Tuolumne. At Rancheria Mountain, where the volcanic "dam" in the ancient channel was highest, the river was forced to shift laterally southward around the dam and adjacent to the volcanic infilling, and start its new channel in granitic bedrock. Near Rancheria Mountain, as much as 1,525 m of new channel incision has taken place in the past 10 m.y., and the modern channel is about 915 m lower than the abandoned channel. An undetermined amount of this downcutting was from glacial erosion. The Tuolumne river system provides no direct evidence for timing the onset of uplift, but the shape of the lO-m.y.-old channel at Rancheria Mountain suggests that uplift had been underway for some time before the volcanic infilling. This timing is compatible with evidence from the upper San Joaquin River. Hetch Hetchy Valley on the Tuolumne is a much "fresher" glaciated valley than is Yosemite Valley. Hetch Hetchy was filled to the brim with glacial ice as recently as 15,000-20,000 yr ago (Tioga glaciation), whereas Yosemite Valley probably has not been filled for 750,000 yr or more (Sherwin glaciation). Thus the upper reaches of Yosemite Valley cliffs have been shaped by spalling rather than by glacial scour and are much more irregular than those in Hetch Hetchy.

California↗
USGS2020

Whitebark pine in the national parks of the Pacific states: An assessment of population vulnerability

Whitebark pine ( Pinus albicaulis ) is a long-lived tree found in high-elevation forests of western North America that is declining due to the non-native white pine blister rust ( Cronartium ribicola ) and climate-driven outbreaks of mountain pine beetle ( Dendroctonus ponderosae ; MPB). The National Park Service established a monitoring program for whitebark pine in seven parks, including Sequoia & Kings Canyon, Yosemite, Lassen Volcanic, Crater Lake, Mount Rainier, Olympic, and North Cascades National Parks. Using these data, we summarized stand structure, presence of blister rust, and MPB prevalence to provide a baseline for future monitoring. Next, we used a stochastic, size-structured population model to speculate on future trends in the seven national park populations under conditions of increased MPB activity and ongoing blister rust infection observed in Crater Lake. We found that blister rust infected 29 to 54% of whitebark pine in all the parks except the two southernmost, Sequoia & Kings Canyon and Yosemite, where infections rates were 0.3% and 0.2%, respectively. The proportion of dead trees in Sequoia & Kings Canyon and Yosemite was low (0 to 1%), while they ranged from 10 to 43% in the other parks. Model projections suggested an average population decline of 25% in the parks over the next century using Crater Lake conditions, declines which are possible if blister rust continues to spread and climate change results in a significant increase in the frequency or severity of MPB outbreaks. Overall, our study describes conditions at seven western parks and illustrates potential rates of whitebark pine decline if pest outbreaks and/or blister rust infections worsen.

California, Oregon, Washington↗
USGS2011

Amphibian chytrid fungus (Batrachochytrium dendrobatidis) in coastal and montane California, USA Anurans

We found amphibian chytrid fungus (Bd = Batrachochytrium dendrobatidis) to be widespread within a coastalwatershed at Point Reyes National Seashore, California and within two high elevation watersheds at Yosemite NationalPark, California. Bd was associated with all six species that we sampled (Bufo boreas, B. canorus, Pseudacris regilla, Ranadraytonii, R. sierrae, and Lithobates catesbeianus). For those species sampled at 10 or more sites within a watershed, thepercentage of Bd-positive sites varied from a low of 20.7% for P. regilla at one Yosemite watershed to a high of 79.6% forP. regilla at the Olema watershed at Point Reyes. At Olema, the percent of Bd-positive water bodies declined each year ofour study (2005-2007). Because P. regilla was the only species found in all watersheds, we used that species to evaluatehabitat variables related to the sites where P. regilla was Bd-positive. At Olema, significant variables were year, length ofshoreline (perimeter), percentage cover of rooted vegetation, and water depth. At the two Yosemite watersheds, waterdepth, water temperature, and silt/mud were the most important covariates, though the importance of these three factorsdiffered between the two watersheds. The presence of Bd in species that are not declining suggests that some of theamphibians in our study were innately resistant to Bd, or had developed resistance after Bd became established.

California↗
USGS2022

Research to inform passage spacing for migratory amphibians and to evaluate efficacy and designs for open elevated road segment (ERS) passages

This is a multifaceted project that includes three main areas of research targeted to inform effective crossing systems for migratory amphibians, a large group of species which are at very high risk from negative impacts from roads within their habitats (Glista et al. 2008, Hamer and McDonnell 2008, Semlitsch 2008, Brehme et al. 2018). The three projects presented in this report are: 1) Movement distances along road barrier fencing and probabilities of reaching a passage: Case study with Yosemite toads in Sierra National Forest, CA. 2) Effectiveness of a novel elevated road segment (ERS) road passage system prototype in providing connectivity for amphibians, reptiles, and small mammals: Case study in Sierra National Forest, CA. 3) Concept designs and transportation engineering evaluation for the ERS on primary roads and highways. This research began in 2018 as part of a larger U.S. Geological Survey (USGS) research program in collaboration with the U.S. Forest Service (USFS), California Department of Transportation (Caltrans), and Western Transportation Institute (WTI; Montana State University) to inform best management practices for barrier and crossing systems for sensitive amphibians and reptiles in California (Langton and Clevenger 2021, Brehme and Fisher 2020). The funding from Department of Transportation (DOT) pooled fund partners (Parks Canada / Government of Canada, Federal Highway Administration (FHWA), U.S. State Departments of Transportation (AK, AZ, CA, CO, IA, MI, MN, NM, NV, OR, WA), Ontario Ministry of Transportation) and managed by the Nevada Department of Transportation (NDOT) supported 2021 field study efforts, analyses of fence movement distances for Yosemite toads, and analysis of the efficacy of a novel ERS passage system to Yosemite toads and other amphibians, reptiles and small mammals. Finally, this pooled fund project includes an assessment by transportation engineers in consultation with USGS and Caltrans to provide insight, guidance, and concept designs for similar crossing solutions that could be implemented on improved roads. This research is meant to inform the distances required between crossings to provide permeability for migratory amphibians (i.e., to allow movements necessary for population persistence across roads) as well as to assess the permeability of a new passage design for amphibians and other small animal species that may provide greater connectivity and offer an alternative to below grade tunnels. The results of these studies add to the current body of knowledge in road ecology and increase the choices of road passage designs for amphibians and other small wildlife species.

California↗