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Articles 451 - 480 of 511
Full-Text Articles in Geology
Reconstructing Late Pleistocene And Holocene Paleoenvironments Using Playa-Lunette System Sediments Within The Harney Basin Of Southeastern Oregon, Usa, Joe Collins
Open Access Theses & Dissertations
Paleoenvironmental investigations of the Late Pleistocene and Early Holocene in the Harney Basin of eastern Oregon have been limited to date. This Dissertation investigates and links the stratigraphy of Rimrock Draw Rockshelter (35HA3855) (RDR) and two surrounding playas, Rimrock Lake and Hay Lake, located on the western margin of the Harney Basin, in order to identify paleoenvironmental shifts during the last ~20 kyr. An emphasis also is given to demonstrating the potential for playas in the Harney Basin to record changes in paleoclimate, as well as the application of multivariate statistics to interpret paleoenvironments from sedimentary grain size data. Stratigraphy …
Regional Geochemical Mapping Of The Superior Upland Province; Ichnology Of The Cretaceous Mesilla Valley Formation, Cerro De Cristo Rey; A New Ichnospecies Of Cardioichnus From The Cretaceous (Albian) Of New Mexico; A Pedagogy For The Cerro De Cristo Rey Tracksite; Walking In The Footprints Of Dino, Eric J. Kappus
Open Access Theses & Dissertations
This is a multi-disciplinary study that covers a variety of geoscience topics on both international borders of the continental United States. This Dissertation is the product of several separate investigations. First is a report on the landscape geochemistry of the Superior Upland Province of Minnesota, Wisconsin, and Michigan, with regional maps of 37 chemical elements interpreted in terms of bedrock, glacial reworking, and anthropogenic influence. The next 2 sections are reports on the invertebrate ichnology of the Cretaceous Mesilla Valley Formation at Cerro de Cristo Rey, including the proposal of a new ichnospecies of echinoid resting trace, Cardioichnus biloba nov. …
Geology And Mineralization Controls Surrounding The Palmarejo Mining District - A Compilation Of Remote And Hands On Exploration Techniques, Castulo Molina Sotelo
Geology And Mineralization Controls Surrounding The Palmarejo Mining District - A Compilation Of Remote And Hands On Exploration Techniques, Castulo Molina Sotelo
Open Access Theses & Dissertations
Exploration is the base of the mining industry, and it is often taken as synonymous with "finding a mine". In reality it is a more complex process; where the selection, evaluation, screening and testing of successively smaller areas lead to the discovery of an economic deposit. Once the deposit is found, the economic factors become more important than the geological ones, and then the exploration becomes a tool to give sustainability to the mining operation through time.
The silver and gold deposits of the world-class Palmarejo District are typical, intermediate sulfidation- style epithermal, precious metal occurrences, hosted in Cretaceous- to …
The Origin Of Anomalous Carbonate Units Outcropping At The Salt Sediment Interface Of The Southern End Of Gypsum Valley Salt Wall, Paradox Basin, Colorado, Allison M. Mast
Open Access Theses & Dissertations
Understanding structural, stratigraphic, and petrographic complexities at the salt-sediment interface of diapirs has important implications in accurately assessing hydrocarbon reservoir quality and near-diapir trap geometries, and may aid in more accurate predictions for locating the true margin of salt in diapiric layered evaporites. The southwest margin of the exhumed Gypsum Valley Salt Wall, Paradox Basin, southwest Colorado, provides a rare view of this interface where onlapping and overlapping wedges of Late Permian and Jurassic halokinetic sequences overlie an angular unconformity truncating near-vertical, highly deformed carbonate beds formerly mapped as Pennsylvanian Honaker Trail Formation. This study investigates three possible alternative origins …
A Geophysical Investigation At The Potrillo Maar, Manuel Moncada Gutierrez
A Geophysical Investigation At The Potrillo Maar, Manuel Moncada Gutierrez
Open Access Theses & Dissertations
The Potrillo Volcanic Field (PVF) is a unique geological site located in Doña Ana County the southernmost part of New Mexico, and part of northern part of Chihuahua, Mexico. The main feature of the southern PVF is Potrillo Maar. This maar-volcano straddles the international boundary between United States and Mexico and lies within the southern part of the Rio Grande Rift. The Potrillo Maar was formed about 20,000 years ago in three major events that formed basalt lava flows and ejecta deposits that consist of crustal and mantle xenoliths.
The purpose of this Thesis is to determine the area of …
Reconstructing Dinosaur Foot Tracks And Identifying New Footprints Using Structure From Motion Photogrammetry, Valeria V. Martinez
Reconstructing Dinosaur Foot Tracks And Identifying New Footprints Using Structure From Motion Photogrammetry, Valeria V. Martinez
Open Access Theses & Dissertations
The use of 3-D Structure from Motion models to study fossils is a relatively new technique that has an advantage over traditional field methods, such as plaster casts or collecting samples, because it is non-destructive and can be easily shared with a wide audience. It is also ideal for use with persons with disabilities because it does not require field access and it can be manipulated for optimum computer viewing or printed with a 3-D printer for tactile examination as needed. Our study focused on a known site in Cristo Rey, New Mexico where Cretaceous Iguanadon and Ankylosaur footprints have …
Kinematic Constraints On Tectonics Of The Northern Basin And Range, Dylan Schmeelk
Kinematic Constraints On Tectonics Of The Northern Basin And Range, Dylan Schmeelk
Graduate Student Theses, Dissertations, & Professional Papers
We derive surface velocities relative to North America, using data from 1989 through 2014 in the interior northwest, to investigate kinematics from the Snake River Plain (SRP) to the Canadian border. The Centennial Tectonic Belt (CTB) exhibits similarities to the main Basin and Range Province (BRP) that suggest the CTB is an extension of the BRP, including range and fault orientation, increasing velocity magnitudes westward, and a distinct high rate of strain across the Madison Range. Calculations of fault spreading rates and orientations from geodetic data show that several faults are more active than previously assumed when compared to seismic …
Glacial Deposits, Vol. 41, 2016, Department Of Geography-Geology
Glacial Deposits, Vol. 41, 2016, Department Of Geography-Geology
Glacial Deposits
Newsletter of the Department of Geography-Geology
Stratigraphy And Extent Of The Pearl-Ashmore Aquifer, Mchenry County, Il, Usa, Drew C. Carlock, Jason F. Thomason, David H. Malone, Eric W. Peterson
Stratigraphy And Extent Of The Pearl-Ashmore Aquifer, Mchenry County, Il, Usa, Drew C. Carlock, Jason F. Thomason, David H. Malone, Eric W. Peterson
Faculty Publications - Geography, Geology, and the Environment
Quaternary glacial till, outwash, lake sediments, and loess compose the surficial deposits of McHenry County, Illinois. Much of the landscape of McHenry County were formed by at least three separate advances of the Harvard Sublobe of the Wisconsin Episode Lake Michigan Lobe, which was part of the Laurentide Ice Sheet. This project focuses on the delineation of the stratigraphy and extent of the Pearl-Ashmore Aquifer. The Pearl-Ashmore Aquifer is the combination of the proglacial outwash of the Wisconsin Episode Ashmore Tongue of the Henry Formation and the youngest outwash associated with the Illinois Episode, which is the Pearl Formation. A …
Land Use Regulation And Access To Amenities: Exploring Spatial Equity Using Gis, Robert B. Thompson
Land Use Regulation And Access To Amenities: Exploring Spatial Equity Using Gis, Robert B. Thompson
Theses
No abstract provided.
Rhyolite And Trachyte Formation At Lake City Caldera: Insight From Quantitative Textural And Geochemical Analyses, Jordan Lubbers
Rhyolite And Trachyte Formation At Lake City Caldera: Insight From Quantitative Textural And Geochemical Analyses, Jordan Lubbers
Dissertations, Master's Theses and Master's Reports
Lake City Caldera (22.93 ± 0.02 Ma) is the youngest of 15 Tertiary calderas found within the Southern Rocky Mountain Volcanic Field (SRMVF). Extreme topographical relief of the area reveals the three dimensional exposure of a complex, high-k calc-alkaline, magmatic system, which provides us with the opportunity to study, in detail, how large silicic magmas evolve in the subsurface. The Lake City igneous system is comprised of two major units: a resurgent syenite intrusion and the Sunshine Peak Tuff (Lower, Middle, and Upper). Bulk-rock analyses indicate that the Lower and Middle Sunshine Peak tuff are crystal poor and rhyolitic in …
Modeling Spring Catchment Discharge: A Case Study Of Candela, Panama, Central America, Jordan P. Van Sickle
Modeling Spring Catchment Discharge: A Case Study Of Candela, Panama, Central America, Jordan P. Van Sickle
Dissertations, Master's Theses and Master's Reports
Where the proper geological and hydrological conditions exist, natural springs have provided a reliable source of clean water to mankind for eons. Changing climates and land development can negatively impact spring source replenishment and threaten their reliability as a source of water. In the face of prospects of diminishing supplies and increasing population demands, community leaders question whether and how to invest in development for enhancing sustainability and protecting water quality, causing water managers to dispute their reliability given decreasing flows. Springs located in the rugged jungle of western Panama serve as the primary water supply for many indigenous communities, …
Neuro-Fuzzy Classification Of Felsic Lava Geomorphology At Alarcon Rise, Mexico, Christina Hefron Maschmeyer
Neuro-Fuzzy Classification Of Felsic Lava Geomorphology At Alarcon Rise, Mexico, Christina Hefron Maschmeyer
Theses and Dissertations
The Alarcon Rise is the only submarine oceanic spreading ridge setting where rhyolitic lavas have been found. This intermediate-rate spreading ridge provides a unique natural laboratory for studying the geomorphology of felsic submarine lava flows at oceanic spreading ridges. Seafloor observations of felsic lava indicate the flow morphology differs from typical submarine basaltic lava at the few other oceanic spreading ridges where differentiated compositions have been recorded. Morphologic variation between mafic and felsic lava flows, especially rhyolites, was also observed at Alarcon Rise.
The Monterey Bay Aquarium Research Institute conducted mapping surveys with autonomous underwater vehicle D Allan B. in …
Submarine Groundwater Discharge And The Configuration Of The Freshwater-Saltwater Interface At The Nearshore And Embayment Scales, Tyler Brandon Evans
Submarine Groundwater Discharge And The Configuration Of The Freshwater-Saltwater Interface At The Nearshore And Embayment Scales, Tyler Brandon Evans
Theses and Dissertations
Submarine groundwater discharge (SGD) rivals riverine discharge to the world’s oceans but remains poorly understood. Until the early 1990’s, geochemical budgets for the ocean were developed using material fluxes from rivers only. SGD has been shown to carry high concentrations of dissolved nutrients, metals and carbon. However, SGD is a difficult to measure, complex phenomenon driven by multiple physical processes. Groundwater flow and the resultant chemical exchange at the land-sea interface are heavily impacted by the hydrodynamic effects of mixing between variable-density fluids. In order to better understand SGD, investigations have focused on the configuration of the freshwater-saltwater interface in …
Late Glacial And Holocene History Of The Penobscot River In The Penobscot Lowland, Maine, Roger Leb. Hooke, Paul R. Hanson, Danile F. Belknap, Alice R. Kelley
Late Glacial And Holocene History Of The Penobscot River In The Penobscot Lowland, Maine, Roger Leb. Hooke, Paul R. Hanson, Danile F. Belknap, Alice R. Kelley
Conservation and Survey Division: Faculty and Staff Publications
When the Laurentide ice sheet retreated rapidly (~150 m/a) across the Penobscot Lowland between ~16 and ~15 ka, the area was isostatically depressed and became inundated by the sea. Silt and clay were deposited, but no significant moraines or deltas were formed. The Penobscot River was reborn at ~14 ka when ice retreated onto land in the upper reaches of the river’s East Branch. As isostatic rebound exceeded sea level rise from melting ice, the river extended itself southward. Between ~13.4 and 12.8 ka, it established a course across marine clay and underlying glacial till in the Lowland. Its gradient …
Coherent Late-Holocene Climate-Driven Shifts In The Structure Of Three Rocky Mountain Lakes, Jeffrey R. Stone, Jasmine E. Saros, Gregory T. Pederson
Coherent Late-Holocene Climate-Driven Shifts In The Structure Of Three Rocky Mountain Lakes, Jeffrey R. Stone, Jasmine E. Saros, Gregory T. Pederson
United States Geological Survey: Staff Publications
Large-scale atmospheric pressure centers, such as the Aleutian and Icelandic Low, have a demonstrated relationship with physical lake characteristics in contemporary monitoring studies, but the responses to these phenomena are rarely observed in lake records. We observe coherent changes in the stratification patterns of three deep (>30 m) lakes inferred from fossil diatom assemblages as a response to shifts in the location and intensity of the Aleutian Low and compare these changes with similar long-term changes observed in the 18O record from the Yukon. Specifically, these records indicate that between 3.2 and 1.4 ka, the Aleutian Low shifted …
Using Satellite Vegetation And Compound Topographic Indices To Maphighly Erodible Cropland Buffers For Cellulosic Biofuel Cropdevelopments In Eastern Nebraska, Usa, Yingxin Gu, Bruce K. Wylie
Using Satellite Vegetation And Compound Topographic Indices To Maphighly Erodible Cropland Buffers For Cellulosic Biofuel Cropdevelopments In Eastern Nebraska, Usa, Yingxin Gu, Bruce K. Wylie
United States Geological Survey: Staff Publications
Cultivating annual row crops in high topographic relief waterway buffers has negative environmental effects and can be environmentally unsustainable. Growing perennial grasses such as switchgrass(Panicum virgatum L.) for biomass (e.g., cellulosic biofuel feedstocks) instead of annual row crops in these high relief waterway buffers can improve local environmental conditions (e.g., reduce soil erosion and improve water quality through lower use of fertilizers and pesticides) and ecosystem services (e.g.,minimize drought and flood impacts on production; improve wildlife habitat, plant vigor, and nitro-gen retention due to post-senescence harvest for cellulosic biofuels; and serve as carbon sinks). The main objectives of this …
Deep Subsurface Drip Irrigation Using Coal-Bed Sodic Water: Part Ii. Geochemistry, Carleton R. Bern, George N. Breit, Richard W. Healy, John W. Zupancic
Deep Subsurface Drip Irrigation Using Coal-Bed Sodic Water: Part Ii. Geochemistry, Carleton R. Bern, George N. Breit, Richard W. Healy, John W. Zupancic
United States Geological Survey: Staff Publications
Waters with low salinity and high sodium adsorption ratios (SARs) present a challenge to irrigation because they degrade soil structure and infiltration capacity. In the Powder River Basin of Wyoming, such low salinity (electrical conductivity, EC 2.1 mS cm−1) and high-SAR (54) waters are co-produced with coal-bed methane and some are used for subsurface drip irrigation (SDI). The SDI system studied mixes sulfuric acid with irrigation water and applies water year-round via drip tubing buried 92 cm deep. After six years of irrigation, SAR values between 0 and 30 cm depth (0.5–1.2) are only slightly increased over non-irrigated …
Geochemical Evidence For Seasonal Controls On The Transportation Of Holocene Loess, Matanuska Valley, Southern Alaska, Usa, Daniel R. Muhs, James R. Budahn, Gary Skipp, John P. Mcgeehin
Geochemical Evidence For Seasonal Controls On The Transportation Of Holocene Loess, Matanuska Valley, Southern Alaska, Usa, Daniel R. Muhs, James R. Budahn, Gary Skipp, John P. Mcgeehin
United States Geological Survey: Staff Publications
Loess is a widespread Quaternary deposit in Alaska and loess accretion occurs today in some regions, such as the Matanuska Valley. The source of loess in the Matanuska Valley has been debated for more than seven decades, with the Knik River and the Matanuska River, both to the east, being the leading candidates and the Susitna River, to the west, as a less favorable source. We report here new stratigraphic, mineralogic, and geochemical data that test the competing hypotheses of these river sources. Loess thickness data are consistent with previous studies that show that a source or sources lay to …
Retrospective: Adjusting Contaminant Concentrations In Bird Eggs To Account For Moisture And Lipid Loss During Their Incubation, Barnett A. Rattner, Stanley N. Wiemeyer, Lawrence J. Blus
Retrospective: Adjusting Contaminant Concentrations In Bird Eggs To Account For Moisture And Lipid Loss During Their Incubation, Barnett A. Rattner, Stanley N. Wiemeyer, Lawrence J. Blus
United States Geological Survey: Staff Publications
By the 1960s, research and monitoring efforts on chlorinated
pesticide residues in tissues of wildlife were well
underway in North America and Europe. Conservationists
and natural resource managers were attempting to resolve
whether pesticide exposure and accumulated residues were
related to population declines in several species of predatory
and scavenging birds (e.g., bald eagle Haliaeetus
leucocephalus, peregrine falcon Falco peregrinus, brown
pelican Pelecanus occidentalis and osprey Pandion haliaetus).
The avian egg was a favored sampling matrix even
before the realization that eggshell thinning was linked to
population declines (Ratcliffe 1967; Hickey and Anderson
1968) and that the …
Component Greenhouse Gas Fluxes And Radiative Balance From Two Deltaic Marshes In Louisiana: Pairing Chamber Techniques And Eddy Covariance, Ken W. Krauss, Guerry O. Holm Jr., Brian C. Perez, David E. Mcwhorter, Nicole Cormier, Rebecca F. Moss, Darren J. Johnson, Scott C. Neubauer, Richard C. Raynie
Component Greenhouse Gas Fluxes And Radiative Balance From Two Deltaic Marshes In Louisiana: Pairing Chamber Techniques And Eddy Covariance, Ken W. Krauss, Guerry O. Holm Jr., Brian C. Perez, David E. Mcwhorter, Nicole Cormier, Rebecca F. Moss, Darren J. Johnson, Scott C. Neubauer, Richard C. Raynie
United States Geological Survey: Staff Publications
Coastal marshes take up atmospheric CO2 while emitting CO2, CH4, and N2O. This ability to sequester carbon (C) is much greater for wetlands on a per area basis than from most ecosystems, facilitating scientific, political, and economic interest in their value as greenhouse gas sinks. However, the greenhouse gas balance of Gulf of Mexico wetlands is particularly understudied. We describe the net ecosystem exchange (NEEc) of CO2 and CH4 using eddy covariance (EC) in comparison with fluxes of CO2, CH4, and N2O using …
Mapping Marginal Croplands Suitable For Cellulosic Feedstock Crops In The Great Plains, United States, Yingxin Gu, Bruce K. Wylie
Mapping Marginal Croplands Suitable For Cellulosic Feedstock Crops In The Great Plains, United States, Yingxin Gu, Bruce K. Wylie
United States Geological Survey: Staff Publications
Growing cellulosic feedstock crops (e.g., switchgrass) for biofuel is more environmentally sustainable than cornbased ethanol. Specifically, this practice can reduce soil erosion and water quality impairment from pesticides and fertilizer, improve ecosystem services and sustainability (e.g., serve as carbon sinks), and minimize impacts on global food supplies. The main goal of this study was to identify high-risk marginal croplands that are potentially suitable for growing cellulosic feedstock crops (e.g., switchgrass) in the US Great Plains (GP). Satellitederived growing season Normalized Difference Vegetation Index, a switchgrass biomass productivity map obtained from a previous study, US Geological Survey (USGS) irrigation and crop …
Evaluating Methods To Establish Habitat Suitability Criteria: A Case Study In The Upper Delaware River Basin, Usa, H. S. Galbraith, C. J. Blakeslee, J. C. Cole, C. A. Talbert, K. O. Maloney
Evaluating Methods To Establish Habitat Suitability Criteria: A Case Study In The Upper Delaware River Basin, Usa, H. S. Galbraith, C. J. Blakeslee, J. C. Cole, C. A. Talbert, K. O. Maloney
United States Geological Survey: Staff Publications
Defining habitat suitability criteria (HSC) of aquatic biota can be a key component to environmental flow science. HSC can be developed through numerous methods; however, few studies have evaluated the consistency of HSC developed by different methodologies. We directly compared HSC for depth and velocity developed by the Delphi method (expert opinion) and by two primary literature meta-analyses (literature- derived range and interquartile range) to assess whether these independent methods produce analogous criteria for multiple species (rainbow trout, brown trout, American shad, and shallow fast guild) and life stages. We further evaluated how these two independently developed HSC affect calculations …
Evaluating Land Cover Influences On Model Uncertainties—A Case Study Of Cropland Carbon Dynamics In The Mid-Continent Intensive Campaign Region, Zhengpeng Li, Shuguang Liu, Xuesong Zhang, Tristram O. West, Stephen M. Ogle, Naijun Zhou
Evaluating Land Cover Influences On Model Uncertainties—A Case Study Of Cropland Carbon Dynamics In The Mid-Continent Intensive Campaign Region, Zhengpeng Li, Shuguang Liu, Xuesong Zhang, Tristram O. West, Stephen M. Ogle, Naijun Zhou
United States Geological Survey: Staff Publications
tQuantifying spatial and temporal patterns of carbon sources and sinks and their uncertainties acrossagriculture-dominated areas remains challenging for understanding regional carbon cycles. Character-istics of local land cover inputs could impact the regional carbon estimates but the effect has not beenfully evaluated in the past. Within the North American Carbon Program Mid-Continent Intensive (MCI)Campaign, three models were developed to estimate carbon fluxes on croplands: an inventory-basedmodel, the Environmental Policy Integrated Climate (EPIC) model, and the General Ensemble biogeo-chemical Modeling System (GEMS) model. They all provided estimates of three major carbon fluxes oncropland: net primary production (NPP), net ecosystem production (NEP), and …
Processes Contributing To Resilience Of Coastal Wetlands To Sea-Level Rise, Camille L. Stagg, Ken W. Krauss, Donald R. Cahoon, Nicole Cormier, William H. Conner, Christopher M. Swarzenski
Processes Contributing To Resilience Of Coastal Wetlands To Sea-Level Rise, Camille L. Stagg, Ken W. Krauss, Donald R. Cahoon, Nicole Cormier, William H. Conner, Christopher M. Swarzenski
United States Geological Survey: Staff Publications
The objectives of this study were to identify processes that contribute to resilience of coastal wetlands subject to rising sea levels and to determine whether the relative contribution of these processes varies across different wetland community types. We assessed the resilience of wetlands to sea-level rise along a transitional gradient from tidal freshwater forested wetland (TFFW) to marsh by measuring processes controlling wetland elevation. We found that, over 5 years of measurement, TFFWs were resilient, although some marginally, and oligohaline marshes exhibited robust resilience to sea-level rise. We identified fundamental differences in how resilience is maintained across wetland community types, …
Conserving California Condors In The 1980s, Noel F.R. Snyder
Conserving California Condors In The 1980s, Noel F.R. Snyder
United States Geological Survey: Staff Publications
By the late 1970s, the California condor (Gymnogyps californianus) was in serious trouble, with probably no more than about 30 birds left in existence, all in a mountainous region just north of Los Angeles that is vegetated mainly in chaparral and grasslands. All estimates of population size and trends offered since the early condor studies by Carl Koford in the 1930s and 1940s indicated a continuing decline toward extinction, and it appeared that few years were left before the species would be gone (see Koford, 1953; Wilbur, 1978). Evidently, the conservation steps that had been taken, including the …
Patuxent’S American Black Duck Studies From Chesapeake Bay To Maine And Beyond, Jerry R. Longcore
Patuxent’S American Black Duck Studies From Chesapeake Bay To Maine And Beyond, Jerry R. Longcore
United States Geological Survey: Staff Publications
The information in this chapter draws on published literature and unpublished reports written by staff members of the U.S. Geological Survey, Patuxent Wildlife Research Center (Patuxent), during its 75-year history. Reports by Bureau of Biological Survey (Biological Survey) and U.S. Fish and Wildlife Service (USFWS) personnel are included because the research entity currently known as Patuxent was formerly administered by these agencies. Some of the cited reports were prepared by USFWS scientists while they were not working at Patuxent. Literature resulting from work at other Federal and State agencies and private and academic institutions that influenced research at Patuxent on …
The Migratory Bird And Habitat Research Laboratory And The Accelerated Research Program, Richard A. Coon
The Migratory Bird And Habitat Research Laboratory And The Accelerated Research Program, Richard A. Coon
United States Geological Survey: Staff Publications
The Patuxent Wildlife Research Center (Patuxent) housed two important programs that were not supervised through the office of the Director of Patuxent during the 1960s and 1970s. Although they received administrative support from Patuxent, they were supervised from the U.S. Fish and Wildlife Service (USFWS) headquarters in Washington, D.C. One, the Migratory Bird Populations Station (MBPS), was established in 1961; the other, the Migratory Bird and Habitat Research Laboratory (MBHRL), was established in 1972 (Perry, 2004). This chapter briefly discusses MBPS and how some of its functions were transferred to MBHRL when this new laboratory was created.
Amino Acid Specific Stable Nitrogen Isotope Values In Avian Tissues: Insights From Captive American Kestrels And Wild Herring Gulls, C.E. Hebert, B.N. Popp, K.J. Fernie, C. Ka’Apu-Lyons, B.A. Rattner, N. Wallsgrove
Amino Acid Specific Stable Nitrogen Isotope Values In Avian Tissues: Insights From Captive American Kestrels And Wild Herring Gulls, C.E. Hebert, B.N. Popp, K.J. Fernie, C. Ka’Apu-Lyons, B.A. Rattner, N. Wallsgrove
United States Geological Survey: Staff Publications
Through laboratory and field studies, the utility of amino acid compound-specific nitrogen isotope analysis (AA-CSIA) in avian studies is investigated. Captive American kestrels (Falco sparverius) were fed an isotopically characterized diet and patterns in δ15N values of amino acids (AAs) were compared to those in their tissues (muscle and red blood cells) and food. Based upon nitrogen isotope discrimination between diet and kestrel tissues, AAs could mostly be categorized as source AAs (retaining baseline δ15N values) and trophic AAs (showing 15N enrichment). Trophic discrimination factors based upon the source (phenylalanine, Phe) and trophic (glutamic acid, Glu) AAs were 4.1 (muscle) …
Non-Linear Responses Of Glaciated Prairie Wetlands To Climate Warming, W. Carter Johnson, Brett Werner, Glenn R. Guntenspergen
Non-Linear Responses Of Glaciated Prairie Wetlands To Climate Warming, W. Carter Johnson, Brett Werner, Glenn R. Guntenspergen
United States Geological Survey: Staff Publications
The response of ecosystems to climate warming is likely to include threshold events when small changes in key environmental drivers produce large changes in an ecosystem. Wetlands of the Prairie Pothole Region (PPR) are especially sensitive to climate variability, yet the possibility that functional changes may occur more rapidly with warming than expected has not been examined or modeled. The productivity and biodiversity of these wetlands are strongly controlled by the speed and completeness of a vegetation cover cycle driven by the wet and dry extremes of climate. Two thresholds involving duration and depth of standing water must be exceeded …