Entity

Time filter

Source Type

Three Rivers, CA, United States

Meyer E.,Sequoia and Kings Canyon National Parks | Meyer E.,California State University, Fresno | Sparling D.,Southern Illinois University Carbondale | Blumenshine S.,California State University, Fresno
Environmental Toxicology and Chemistry | Year: 2013

The present study investigated the potential effects of cholinesterase (ChE)-inhibiting pesticides on western pond turtles (Emys marmorata) occupying streams in two regions of California, USA. The southern region was suspected of having increased exposure to atmospheric deposition of contaminants originating from Central Valley agriculture. The northern region represented reference ChE activities because this area was located outside of the prominent wind patterns that deposit pesticides into the southern region. Total ChE activity was measured in plasma from a total of 81 turtles from both regions. Cholinesterase activity of turtles was significantly depressed by 31% (p=0.005) in the southern region after accounting for additional sources of variation in ChE activity. Male turtles had significantly increased ChE activity compared with females (p=0.054). Cloaca temperature, length, mass, handling time, body condition, and lymph presence were not significant predictors of turtle ChE activity. In the southern region, 6.3% of the turtles were below the diagnostic threshold of two standard deviations less than the reference site mean ChE activity. Another diagnostic threshold determined that 75% of the turtles from the southern region had ChE activities depressed by 20% of the reference mean. The decrease in ChE activity in the southern region suggests sublethal effects of pesticide exposure, potentially altering neurotransmission, which can result in various deleterious behaviors. Environ. Toxicol. Chem. 2013;32:692-698. © 2012 SETAC Copyright © 2012 SETAC. Source


Mazur R.L.,Sequoia and Kings Canyon National Parks
Journal of Wildlife Management | Year: 2010

Aversive conditioning (AC) has the potential to temporarily reduce conflicts between humans and black bears (Ursus americanus). From 2002 to 2005, I evaluated the effectiveness of projectiles with varying impact intensities, pepper spray, and chasing on approximately 150 bears in Sequoia National Park. Aversive conditioning was successful in keeping bears that were not food-conditioned from becoming food-conditioned. For the bears that were already food-conditioned, 17 of 29 bears subjected to AC abandoned unwanted behaviors, 6 required continual treatments, and 6 were killed or relocated. Success with food-conditioned bears was highest when AC was applied soon after bears obtained human food. Aversive conditioning was less successful on yearlings than adults. Rubber slugs were slightly more effective than lower impact projectiles. © 2010 The Wildlife Society. Source


Holmquist J.G.,University of California White Mountain Research Station | Schmidt-Gengenbach J.,University of California White Mountain Research Station | Haultain S.A.,Sequoia and Kings Canyon National Parks
Wetlands | Year: 2010

Pack stock are often used in mountain environments and are grazed in uplands and wetlands, particularly subalpine wet meadows. Effects of pack stock on wetland invertebrates are unknown. Sequoia National Park, (Sierra Nevada, USA), was an ideal location for the study of lasting stock impacts on fauna, because a) there was an 18- year database of stock usage, b) there were meadows with little grazing that could be contrasted with grazed meadows, c) there is a long winter with no stock use, and d) the start of grazing for each meadow is controlled, so we could sample after greenup but just before stock arrived. We could thus address persistent conditions produced by many years of stock use in isolation from any potential short term impacts. We sampled terrestrial arthropods in paired "grazed" and "ungrazed" meadows across the Park and collected associated vegetation data. We found some negative effects of grazing on vegetation structure, but few lasting negative or positive effects of long-term stock grazing on arthropods in these wetlands. Although it appears that pack stock do not cause lasting damage to this arthropod assemblage, the extent of impact at the height of the grazing season remains unknown. © Society of Wetland Scientists 2010. Source


Schwilk D.W.,Texas Tech University | Caprio A.C.,Sequoia and Kings Canyon National Parks
Journal of Ecology | Year: 2011

1.Although species differ in flammability, identifying the traits that influence flammability and linking them to other axes of trait variation has yet to be accomplished. Leaf length may be a key trait influencing the flammability of leaf litter. 2.Differences in species composition across a landscape or changes in composition through time may alter fire behaviour. Forests in the Sierra Nevada of CA, USA, have experienced changes in species composition that have modified the distribution of leaf litter traits. 3.Across three independent data sets, at scales from a single watershed to multiple watersheds and elevations, we tested if mean community leaf length in patterns of fire severity. We used structural equation models to disentangle direct effects of site characteristics from the contribution of species composition. 4.Fire severity was greater at sites inhabited by species with longer leaves than at sites containing short-leaved species, probably as a result of lower litter density. The effect cannot be explained merely by the joint influence of site characteristics on both fire behaviour and species composition. 5.A significant portion of this pattern is driven by shifts in the abundance of Pinus species. In this system, pines are among the longest-leaved species and this makes it difficult to separate leaf-length effects from other possible flammability-enhancing characteristics of pines. Evidence from one data set, however, suggests that the pattern cannot be entirely explained by proportion of pines alone. 6.Synthesis. We demonstrate that a simple integration of a species trait predicts fire severity at landscape scales. This provides a link between the two scales at which most previous work has occurred: species-specific measurements of traits and landscape-level characterisation of fuel loads. Investigations of trait effects on fire behaviour are important because climate change may lead to novel climates and no-analogue species assemblages. In this ecosystem, shorter-leaved species, which have increased in density during the period of fire exclusion, may act as a positive feedback by reducing fire severity and thereby favouring their own establishment. Conversely, restoration of fire to these forests, by increasing the dominance of long-leaved species, may increase flammable fuels. © 2011 British Ecological Society. No claim to original US government works. Source


Nesmith J.C.B.,University of California at Berkeley | Caprio A.C.,Sequoia and Kings Canyon National Parks | Pfaff A.H.,U.S. Geological Survey | McGinnis T.W.,U.S. Geological Survey | Keeley J.E.,U.S. Geological Survey
Forest Ecology and Management | Year: 2011

Current goals for prescription burning are focused on measures of fuel consumption and changes in forest density. These benchmarks, however, do not address the extent to which prescription burning meets perceived ecosystem needs of heterogeneity in burning, both for overstory trees and understory herbs and shrubs. There are still questions about how closely prescribed fires mimic these patterns compared to natural wildfires. This study compared burn patterns of prescribed fires and managed unplanned wildfires to understand how the differing burning regimes affect ecosystem properties. Measures of forest structure and fire severity were sampled in three recent prescribed fires and three wildfires managed for resource objectives in Sequoia and Kings Canyon National Parks. Fine scale patterns of fire severity and heterogeneity were compared between fire types using ground-based measures of fire effects on fuels and overstory and understory vegetation. Prescribed fires and wildfires managed for resource objectives displayed similar patterns of overstory and understory fire severity, heterogeneity, and seedling and sapling survival. Variation among plots within the same fire was always greater than between fire types. Prescribed fires can provide burned landscapes that approximate natural fires in many ways. It is recognized that constraints placed on when wildfires managed for resource objectives are allowed to burn freely may bias the range of conditions that might have been experienced under more natural conditions. Therefore they may not exactly mimic natural wildfires. Overall, the similarity in fire effects that we observed between prescribed fires and managed wildfires indicate that despite the restrictions that are often placed on prescribed fires, they appear to be creating post-fire conditions that approximate natural fires when assessed on a fine spatial scale. © 2011. Source

Discover hidden collaborations