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2012

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Articles 841 - 870 of 988

Full-Text Articles in Earth Sciences

Identifying Risk Factors For Disparities In Breast Cancer Mortality Among African-American And Hispanic Women, Nancy Tian, Pierre Goovaerts, F. Benjamin Zhan, T. Edwin Chow, Jeff Gaines Wilson Jan 2012

Identifying Risk Factors For Disparities In Breast Cancer Mortality Among African-American And Hispanic Women, Nancy Tian, Pierre Goovaerts, F. Benjamin Zhan, T. Edwin Chow, Jeff Gaines Wilson

School of Earth, Environmental, & Marine Sciences Faculty Publications

Background: This study evaluated the risk factors associated with racial disparities in female breast cancer mortality for African-American and Hispanic women at the census tract level in Texas from 1995 to 2005.

Methods: Data on female breast cancer cases were obtained from the Texas Cancer Registry. Socioeconomic and demographic data were collected from Census 2000. Network distance and driving times to mammography facilities were estimated using Geographic Information System techniques. Demographic, poverty and spatial accessibility factors were constructed using principal component analysis. Logistic regression models were developed to predict the census tracts with significant racial disparities in breast cancer mortality …


Effects Of Hypoxia Exposure On Hepatic Cytochrome P450 1a (Cyp1a) Expression In Atlantic Croaker: Molecular Mechanisms Of Cyp1a Down-Regulation, Md. Saydur Rahman, Peter Thomas Jan 2012

Effects Of Hypoxia Exposure On Hepatic Cytochrome P450 1a (Cyp1a) Expression In Atlantic Croaker: Molecular Mechanisms Of Cyp1a Down-Regulation, Md. Saydur Rahman, Peter Thomas

School of Earth, Environmental, & Marine Sciences Faculty Publications

Hypoxia-inducible factor-α (HIF-α) and cytochrome P450 1A (CYP1A) are biomarkers of environmental exposure to hypoxia and organic xenobiotic chemicals that act through the aryl hydrocarbon receptor, respectively. Many aquatic environments heavily contaminated with organic chemicals, such as harbors, are also hypoxic. Recently, we and other scientists reported HIF-α genes are upregulated by hypoxia exposure in aquatic organisms, but the molecular mechanisms of hypoxia regulation of CYP1A expression have not been investigated in teleost fishes. As a first step in understanding the molecular mechanisms of hypoxia modulation of CYP1A expression in fish, we characterized CYP1A cDNA from croaker liver. Hypoxia exposure …


Landscape-Level Controls On Dissolved Carbon Flux From Diverse Catchments Of The Circumboreal, Suzanne E. Tank, Karen E. Frey, Robert G. Striegl, Peter A. Raymond, Robert M. Holmes, James W. Mcclelland, Bruce J. Peterson Jan 2012

Landscape-Level Controls On Dissolved Carbon Flux From Diverse Catchments Of The Circumboreal, Suzanne E. Tank, Karen E. Frey, Robert G. Striegl, Peter A. Raymond, Robert M. Holmes, James W. Mcclelland, Bruce J. Peterson

Geography

While much of the dissolved organic carbon (DOC) within rivers is destined for mineralization to CO2, a substantial fraction of riverine bicarbonate (HCO3-) flux represents a CO2 sink, as a result of weathering processes that sequester CO2 as HCO 3-. We explored landscape-level controls on DOC and HCO3- flux in subcatchments of the boreal, with a specific focus on the effect of permafrost on riverine dissolved C flux. To do this, we undertook a multivariate analysis that partitioned the variance attributable to known, key regulators of dissolved C flux (runoff, lithology, and vegetation) prior to examining the effect of permafrost, …


Plate Kinematics Of The Afro-Arabian Rift System With An Emphasis On The Afar Depression, Helen Carrie Bottenberg Jan 2012

Plate Kinematics Of The Afro-Arabian Rift System With An Emphasis On The Afar Depression, Helen Carrie Bottenberg

Doctoral Dissertations

This work utilizes the Four-Dimensional Plates (4DPlates) software, and Differential Interferometric Synthetic Aperture Radar (DInSAR) to examine plate-scale, regional-scale and local-scale kinematics of the Afro-Arabian Rift System with emphasis on the Afar Depression in Ethiopia. First, the 4DPlates is used to restore the Red Sea, the Gulf of Aden, the Afar Depression and the Main Ethiopian Rift to development of a new model that adopts two poles of rotation for Arabia. Second, the 4DPlates is used to model regional-scale and local-scale kinematics within the Afar Depression. Most plate reconstruction models of the Afro-Arabian Rift System relies on considering the Afar …


Process-Evaluation Of Tropospheric Humidity Simulated By General Circulation Models Using Water Vapor Isotopic Observations: 2. Using Isotopic Diagnostics To Understand The Mid And Upper Tropospheric Moist Bias In The Tropics And Subtropics, Camille Risi, David Noone, John Worden, Christian Frankenberg, Gabriele Stiller, Michael Kiefer, Bernd Funke, Kaley Walker, Peter Bernath, Matthias Schneider, Sandrine Bony, Jeonghoon Lee, Derek Brown, Christophe Sturm Jan 2012

Process-Evaluation Of Tropospheric Humidity Simulated By General Circulation Models Using Water Vapor Isotopic Observations: 2. Using Isotopic Diagnostics To Understand The Mid And Upper Tropospheric Moist Bias In The Tropics And Subtropics, Camille Risi, David Noone, John Worden, Christian Frankenberg, Gabriele Stiller, Michael Kiefer, Bernd Funke, Kaley Walker, Peter Bernath, Matthias Schneider, Sandrine Bony, Jeonghoon Lee, Derek Brown, Christophe Sturm

Chemistry & Biochemistry Faculty Publications

Evaluating the representation of processes controlling tropical and subtropical tropospheric relative humidity (RH) in atmospheric general circulation models (GCMs) is crucial to assess the credibility of predicted climate changes. GCMs have long exhibited a moist bias in the tropical and subtropical mid and upper troposphere, which could be due to the mis-representation of cloud processes or of the large-scale circulation, or to excessive diffusion during water vapor transport. The goal of this study is to use observations of the water vapor isotopic ratio to understand the cause of this bias. We compare the three-dimensional distribution of the water vapor isotopic …


Impacts Of Land Use/Land Cover And Soil On Water Quality In The Upper Little Miami River Sub-Basin, Devendra Kumar Akshaya Jan 2012

Impacts Of Land Use/Land Cover And Soil On Water Quality In The Upper Little Miami River Sub-Basin, Devendra Kumar Akshaya

Browse all Theses and Dissertations

The Little Miami River Basin (LMRB) is increasingly becoming susceptible to the degradation of water quality due to various factors such as increase in urban landscape and agricultural runoff. This study is about understanding the impact of land use/land cover (LULC) and soil on water quality in LMRB. It was assumed that the major sources of solutes in the river mainly originated from the leaching of the land by precipitation and the composition of the leachate is influenced by the type LULC and soil. Least square method was modified to estimate the production coefficient for each of the types of …


Relationship Between Log Permeability And Fraction Of Finer Grains In Bimodal Sediment Mixtures, Steven M. Verdibello Jan 2012

Relationship Between Log Permeability And Fraction Of Finer Grains In Bimodal Sediment Mixtures, Steven M. Verdibello

Browse all Theses and Dissertations

In sediment mixtures of two grain-size components, the mixture porosity (Φ) and permeability (k) both vary non-linearly as a function of the grain size and the volume fraction of each component. A porosity minimum (Φmin) occurs near the mixture fraction at which the volume of the finer grains equals the original pore volume of the coarser grains. An abrupt change in slope has been observed in the non-linear relationship between log(k) and the volume fraction of finer grains (rf). This slope change should occur at the rf where coarser pore pathways change from continuous to discontinuous. In this study, fine …


A Geophysical Investigation Searching For Archaeological Features At Sunwatch Indian Village, Danielle Torridi Jan 2012

A Geophysical Investigation Searching For Archaeological Features At Sunwatch Indian Village, Danielle Torridi

Browse all Theses and Dissertations

A near-surface geophysical survey was conducted at SunWatch Indian Village in Dayton, Ohio. The main motivations for this investigation were to evaluate geophysical methods to locate, map, and identify features associated with the SunWatch Indian Village archaeological site and to expand the area surveyed. Previous studies (Houston, 2002; Miller, 2004) have determined that burials covered with limestone slabs are relatively easy to detect and map geophysically with GPR and electrical resistivity. This was reconfirmed in this study by collecting 3D GPR data over a 'control' location previously surveyed by Houston (2002) and Miller (2004). However, similar anomalies were not observed …


The Influence Of Streambed Heterogeneity On Hyporheic Exchange In Gravelly Rivers, Yaoquan Zhou Jan 2012

The Influence Of Streambed Heterogeneity On Hyporheic Exchange In Gravelly Rivers, Yaoquan Zhou

Browse all Theses and Dissertations

Hyporheic exchange can be influenced by channel meanders, by streambed topography, and by the heterogeneity within subsurface sediments. Fluvial systems with streambed sediments composed of sandy gravel can be heterogeneous and contain open-framework gravel stratasets that comprise roughly one-third of the sedimentary deposit by volume. The open-framework gravel stratasets have an average lateral length scale on the order of 10 m, average thickness on the order of a decimeter, and an average dip on the order of 10 degrees downstream. The hydraulic conductivity of open-framework gravel stratasets is on the order of 10-1 m/s, and for the larger volume of …


Evaluating The Effect Of Hyporheic Exchange On Intake Temperatures Of Open-Loop Geothermal Wells In Glacigenic Outwash Aquifers, Nathan Grigsby Jan 2012

Evaluating The Effect Of Hyporheic Exchange On Intake Temperatures Of Open-Loop Geothermal Wells In Glacigenic Outwash Aquifers, Nathan Grigsby

Browse all Theses and Dissertations

Subsurface heat flow was simulated to study the effect of hyporheic exchange on groundwater intake temperatures of open-loop geothermal wells in glacigenic-outwash aquifers in the North American midcontinent. The model represents an aquifer kilometers wide, on the order of 100m thick, and directly connected to a perennial river. The aquifer has bimodal hydraulic conductivity with a geometric mean on the order of 100m/day, an effective thermal conductivity of 2.33W/mK, and specific heats on the order of 106J/(m^3 K) for water and 103J/kgK for solids. The aquifer is initially set to a temperature of 12.85 °C and the river is fixed …


Cometabolic Degradation Of Halogenated Aliphatic Hydrocarbons By Aerobic Microorganisms Naturally Associated With Wetland Plant Roots, Madelyn M. Smith Jan 2012

Cometabolic Degradation Of Halogenated Aliphatic Hydrocarbons By Aerobic Microorganisms Naturally Associated With Wetland Plant Roots, Madelyn M. Smith

Browse all Theses and Dissertations

Wetland systems provide both anaerobic (reducing) and aerobic (oxidizing) zones for the biodegradation of chlorinated aliphatic hydrocarbons (CAH). In particular, wetland plant roots provide micro-oxidizing environments for methanotrophic bacteria from the presence of methane, which is produced in anaerobic zones, and oxygen, which is brought to the subsurface by roots of wetland plants; this shows the potential for cometabolic degradation of common organic pollutants.

This study explored the natural attenuation of CAHs by methanotrophic bacteria naturally associated with roots of the common wetland plant, Carex comosa. Root microcosms were amended with varying concentrations of methane; trichloroethene; cis 1,2-dichloroethene; 1,2-dichloroethane; or …


Why Is There Such A High Concentration Of Vertebrate Remains Within A Bone-Bed Along Clapp Creek, Williamsburg County, South Carolina?, Jennifer R. Soehner Jan 2012

Why Is There Such A High Concentration Of Vertebrate Remains Within A Bone-Bed Along Clapp Creek, Williamsburg County, South Carolina?, Jennifer R. Soehner

Browse all Theses and Dissertations

A phosphatic bone-bed occurs along Clapp Creek in Kingstree, South Carolina, within the east-central portion of the coastal plain. The location of the research site is within the Chicora Member of the Williamsburg Formation. The paleoenvironment of this site was most likely a complex estuary with microenvironments that included tidal channels, tidal deltas, tidal flats, marshes and subtidal bays. The high diversity and large time span in the bone-bed is explained by the transgressive environment and storm deposits. The phosphate content of the bone-bed is from the calcium phosphate occurring in the coprolites of carnivores and the higher concentration of …


Phosphorus Mass Balance For Hypertrophic Grand Lake St. Marys, Ohio, Astrea Taylor Jan 2012

Phosphorus Mass Balance For Hypertrophic Grand Lake St. Marys, Ohio, Astrea Taylor

Browse all Theses and Dissertations

A phosphorus (P) budget was created for Grand Lake St Marys (GLSM), a hypertrophic lake in Ohio with a highly agricultural watershed. Inputs totaled 71,200 ± 8,400 kg P, with tributaries contributing the majority of P inputs at 60,100 ± 4,500 kg P (84%). Other inputs included benthic flux at 9% (internal loading), point-source discharges into streams at 5%, and atmospheric deposition at 1%. Rainfall in 2011 was greater than average, which may affect results when comparing this P budget to years with average rainfall. Transport of P by two rivers draining GLSM was approximately three times greater than benthic …


Change In Shoreline Position For Two Consecutive Years Using Lidar Along The Outer Banks, North Carolina, Rachel Marie Taylor Jan 2012

Change In Shoreline Position For Two Consecutive Years Using Lidar Along The Outer Banks, North Carolina, Rachel Marie Taylor

Browse all Theses and Dissertations

The signal of shoreline change for the Outer Banks, North Carolina is non-stationary. A baseline, west of the first line of dunes, is created for each 5 km section and shore-perpendicular profiles constructed every 20 meters in the alongshore direction. The profiles are obtained from two light detection and ranging (LIDAR) surveys performed in June 22, 2006 and July 7 and 8, 2007.

For five selected sections of coast, Fourier analysis of the shoreline change signal indicates the signal is self-affine i.e. the mean is not stationary, but changes with position along the signal (Malumud and Turcotte, 1999) with a …


Degradation Of Chlorinated Hydrocarbons In Groundwater Passing Through The Treatment Wetland At Wright-Patterson Air Force Base: Analysis Of Results Collected During 2001-'06, Annamarie F. Therrien Jan 2012

Degradation Of Chlorinated Hydrocarbons In Groundwater Passing Through The Treatment Wetland At Wright-Patterson Air Force Base: Analysis Of Results Collected During 2001-'06, Annamarie F. Therrien

Browse all Theses and Dissertations

Constructed wetlands are an efficient and cost effective means for chlorinated aliphatic hydrocarbon remediation, and will therefore continue to gain momentum as an accepted treatment by the US EPA (U.S. EPA, 1995; Amarante, 2000; Lien, 2001; WETPOL, 2009). The treatment options for chlorinated aliphatic hydrocarbons (CAHs), including wetlands, capitalize on aerobic/anaerobic interfaces in which bacterially mediated reduction-oxidation reactions degrade pollutants (Li, 1997; Bradley, 1998; Lorah and Voytek, 2004; Amon, 2007; Imfeld, 2008). In August 2000, researchers at Wright State University (WSU) combined efforts with the United States Air Force Institute of Technology (AFIT) to construct a pilot-scale upward-flow treatment wetland …


Normal Fault Trace-Length Scaling In A Tectonic Transition Zone In Southern Sedna Planitia, Venus, Andrew W. Lyda Jan 2012

Normal Fault Trace-Length Scaling In A Tectonic Transition Zone In Southern Sedna Planitia, Venus, Andrew W. Lyda

Browse all Theses and Dissertations

In this study, fault trace-lengths of normal faults are measured in southern Sedna Planitia, Venus between 27° to 32° latitude and 336° to 343° longitude where smooth, lowland plains transition into highland regions which are broken by basin and range style tectonics. The fault trace-lengths are plotted on a cumulative number verses length plot (CNL) and fit with a power function, exponential function, and logarithmic function to determine which function best describes the trace-length distribution. A power function is the best fit with a scaling exponent of 1.73. This result is compared to previous studies of fault trace-lengths on Venus, …


Neotectonic Evolution Of An Actively Growing Superimposed Basin In Western Anatolia: The Inner Bay Of İzmir, Turkey, Bora Uzel, Hasan Sözbi̇li̇r, Çağlar Özkaymak Jan 2012

Neotectonic Evolution Of An Actively Growing Superimposed Basin In Western Anatolia: The Inner Bay Of İzmir, Turkey, Bora Uzel, Hasan Sözbi̇li̇r, Çağlar Özkaymak

Turkish Journal of Earth Sciences

İzmir Bay is an actively growing shallow marine basin controlled by active faults trending NE, NW, N-S and E-W, in the West Anatolian Extensional Province. The bay of İzmir is a lazy L-shaped superimposed basin which is topographically divided into an E-W-trending inner bay and a NW-trending outer bay. The Inner Bay of İzmir is an asymmetric graben structure approximately 5-7 km wide and 25 km long containing (i) upper Cretaceous-Palaeocene basement, (ii) an older succession of lower to upper Miocene basin fill, overlain with angular unconformity by (iii) a younger Plio-Quaternary basin fill. The older succession contain a 0.5- …


Organic Matter Of Fossil Origin In The Amberine Speleothems From El Soplao Cave (Cantabria, Northern Spain), Fernando Gázquez, Jose Maria Calaforra, Fernando Rull, Paolo Forti, Antonio García-Casco Jan 2012

Organic Matter Of Fossil Origin In The Amberine Speleothems From El Soplao Cave (Cantabria, Northern Spain), Fernando Gázquez, Jose Maria Calaforra, Fernando Rull, Paolo Forti, Antonio García-Casco

International Journal of Speleology

Unusual amberine-coloured speleothems were recently found in El Soplao Cave (Cantabria, Spain). Chromophore elements such as Fe, Mn, Cd, Co or Ti were not present in significant quantities. Rather, our data show that their colour comes from leachates of fossilized organic material hosted in the carbonaceous Urgonian facies of the host rock. These leachates are related to the Cretaceous amber deposit that has been recently discovered in the vicinity of El Soplao Cave. The presence of humic and fulvic acids of fossil origin were confirmed by IR and Raman spectroscopic analysis of the carbonaceous strata and the speleothems. In addition, …


World Karst Science Reviews Jan 2012

World Karst Science Reviews

International Journal of Speleology

No abstract provided.


2d And 3d Imaging Of The Metamorphic Carbonates At Omalos Plateau/Polje, Crete, Greece By Employing Independent And Joint Inversion On Resistivity And Seismic Data, Hamdan Ali Hamdan Dr, Nikos Economou, Giorgos Kritikakis, Nikos Andronikidis, Emmanuil Manoutsoglou, Antonis Vafidis, Pangratis Pangratis, Georgina Apostolidou Jan 2012

2d And 3d Imaging Of The Metamorphic Carbonates At Omalos Plateau/Polje, Crete, Greece By Employing Independent And Joint Inversion On Resistivity And Seismic Data, Hamdan Ali Hamdan Dr, Nikos Economou, Giorgos Kritikakis, Nikos Andronikidis, Emmanuil Manoutsoglou, Antonis Vafidis, Pangratis Pangratis, Georgina Apostolidou

International Journal of Speleology

A geophysical survey carried out at Omalos plateau in Chania, Western Crete, Greece employed seismic as well as electrical tomography methods in order to image karstic structures and the metamorphic carbonates (Tripali unit and Plattenkalk group) which are covered by post-Mesozoic deposits (terra rossa, clays, sands and gravels). The geoelectrical sections image the metamorphic carbonates which exhibit a highly irregular relief. At the central part of the plateau the thickness of post-Mesozoic deposits (terra rossa, clays, sands and gravels) ranges from 40-130 m. A 3D resistivity image was generated by inverting resistivity data collected on a grid to the south …


Cover: Volume 41, Issue 2 Jan 2012

Cover: Volume 41, Issue 2

International Journal of Speleology

No abstract provided.


Guidebook To The Geology Of The Platte River Valley Between Duncan And Schuyler, Nebraska, P.R. Hanson, Robert Matthew Joeckel, Aaron R. Young, Dana Divine, Jesse T. Korus Dr. Jan 2012

Guidebook To The Geology Of The Platte River Valley Between Duncan And Schuyler, Nebraska, P.R. Hanson, Robert Matthew Joeckel, Aaron R. Young, Dana Divine, Jesse T. Korus Dr.

Conservation and Survey Division: Faculty and Staff Publications

The Platte River is considered to be a classic example of a braided stream, that is, a comparatively shallow stream with a high width:depth ratio.


Quantification Of Salt Dust Pathways From A Groundwater-Fed Lake: Implications For Solute Budgets And Dust Emission Rates, Vitaly A. Zlotnik, John B. Ong, John D. Lenters, Jens Schmieder, Sherilyn C. Fritz Jan 2012

Quantification Of Salt Dust Pathways From A Groundwater-Fed Lake: Implications For Solute Budgets And Dust Emission Rates, Vitaly A. Zlotnik, John B. Ong, John D. Lenters, Jens Schmieder, Sherilyn C. Fritz

Department of Earth and Atmospheric Sciences: Faculty Publications

Emissions of salt dust from the shores of saline lakes significantly impact lake chemistry, air quality, transportation, human health, and climate. Quantitative methods for assessing these emissions, however, are still in the developmental stage. We investigate salt pathways from groundwater to dust using an approach that takes advantage of opportune conditions at a groundwater-fed, saline lake in the Nebraska Sand Hills region. The mass of salt in the lakeshore surface crust and soil was measured, as well as in the dust on the surrounding dune field. These data, together with information on the lake hydrology, show that dust emission is …


Groundwater Depletion And Sustainability Of Irrigation In The Us High Plains And Central Valley, Bridget R. Scanlon, Claudia C. Faunt, Laurent Longuevergne, Robert C. Reedy, William M. Alley, Virginia L. Mcguire, Peter B. Mcmahon Jan 2012

Groundwater Depletion And Sustainability Of Irrigation In The Us High Plains And Central Valley, Bridget R. Scanlon, Claudia C. Faunt, Laurent Longuevergne, Robert C. Reedy, William M. Alley, Virginia L. Mcguire, Peter B. Mcmahon

United States Geological Survey: Staff Publications

Aquifer overexploitation could significantly impact crop production in the United States because 60% of irrigation relies on groundwater. Groundwater depletion in the irrigated High Plains and California Central Valley accounts for ∼50% of groundwater depletion in the United States since 1900. A newly developed High Plains recharge map shows that high recharge in the northern High Plains results in sustainable pumpage, whereas lower recharge in the central and southern High Plains has resulted in focused depletion of 330 km3 of fossil groundwater, mostly recharged during the past 13,000 y. Depletion is highly localized with about a third of depletion …


Airborne Electromagnetic Imaging Of Discontinuous Permafrost, Burke J. Minsley, Jared D. Abraham, Bruce D. Smith, James C. Cannia, Clifford I. Voss, M. Torre Jorgenson, Michelle A. Walvoord, Bruce K. Wylie, Lesleigh Anderson, Lyndsay B. Ball, Maryla Deszcz-Pan, Tristan P. Wellman, Thomas A. Ager Jan 2012

Airborne Electromagnetic Imaging Of Discontinuous Permafrost, Burke J. Minsley, Jared D. Abraham, Bruce D. Smith, James C. Cannia, Clifford I. Voss, M. Torre Jorgenson, Michelle A. Walvoord, Bruce K. Wylie, Lesleigh Anderson, Lyndsay B. Ball, Maryla Deszcz-Pan, Tristan P. Wellman, Thomas A. Ager

United States Geological Survey: Staff Publications

The evolution of permafrost in cold regions is inextricably connected to hydrogeologic processes, climate, and ecosystems. Permafrost thawing has been linked to changes in wetland and lake areas, alteration of the groundwater contribution to stream flow, carbon release, and increased fire frequency. But detailed knowledge about the dynamic state of permafrost in relation to surface and groundwater systems remains an enigma. Here, we present the results of a pioneering ~1,800 line-kilometer airborne electromagnetic survey that shows sediments deposited over the past ~4 million years and the configuration of permafrost to depths of ~100 meters in the Yukon Flats area near …


Effects Of Biotic Disturbances On Forest Carbon Cycling In The United States And Canada, Jeffrey A. Hicke, Craig D. Allen, Ankur R. Desai, Michael C. Dietze, Ronald J. Hall, Edward (Ted) H. Hogg, Daniel M. Kashian, David Moore, Kenneth F. Raffa, Rona N. Sturrock, James Vogelmann Jan 2012

Effects Of Biotic Disturbances On Forest Carbon Cycling In The United States And Canada, Jeffrey A. Hicke, Craig D. Allen, Ankur R. Desai, Michael C. Dietze, Ronald J. Hall, Edward (Ted) H. Hogg, Daniel M. Kashian, David Moore, Kenneth F. Raffa, Rona N. Sturrock, James Vogelmann

United States Geological Survey: Staff Publications

Forest insects and pathogens are major disturbance agents that have affected millions of hectares in North America in recent decades, implying significant impacts to the carbon (C) cycle. Here, we review and synthesize published studies of the effects of biotic disturbances on forest C cycling in the United States and Canada. Primary productivity in stands was reduced, sometimes considerably, immediately following insect or pathogen attack. After repeated growth reductions caused by some insects or pathogens or a single infestation by some bark beetle species, tree mortality occurred, altering productivity and decomposition. In the years following disturbance, primary productivity in some …


Do Bioclimate Variables Improve Performance Of Climate Envelope Models?, James I. Watling, Stephanie S. Romanach, David N. Bucklin, Carolina Speroterra, Laura A. Brandt, Leonard G. Pearlstine, Frank J. Mazzotti Jan 2012

Do Bioclimate Variables Improve Performance Of Climate Envelope Models?, James I. Watling, Stephanie S. Romanach, David N. Bucklin, Carolina Speroterra, Laura A. Brandt, Leonard G. Pearlstine, Frank J. Mazzotti

United States Geological Survey: Staff Publications

Climate envelope models are widely used to forecast potential effects of climate change on species distributions. A key issue in climate envelope modeling is the selection of predictor variables that most directly influence species. To determine whether model performance and spatial predictions were related to the selection of predictor variables, we compared models using bioclimate variables with models constructed from monthly climate data for twelve terrestrial vertebrate species in the southeastern USA using two different algorithms (random forests or generalized linear models), and two model selection techniques (using uncorrelated predictors or a subset of user-defined biologically relevant predictor variables). There …


History And Evaluation Of National-Scale Geochemical Data Sets For The United States, David B. Smith, Steven M. Smith, John D. Horton Jan 2012

History And Evaluation Of National-Scale Geochemical Data Sets For The United States, David B. Smith, Steven M. Smith, John D. Horton

United States Geological Survey: Staff Publications

Six national-scale, or near national-scale, geochemical data sets for soils or stream sediments exist for the United States. The earliest of these, here termed the ‘Shacklette’ data set, was generated by a U.S. Geological Survey (USGS) project conducted from 1961 to 1975. This project used soil collected from a depth of about 20 cm as the sampling medium at 1323 sites throughout the conterminous U.S. The National Uranium Resource Evaluation Hydrogeochemical and Stream Sediment Reconnaissance (NUREHSSR) Program of the U.S. Department of Energy was conducted from 1975 to 1984 and collected either stream sediments, lake sediments, or soils at more …


Remote Sensing Of Evapotranspiration For Operational Drought Monitoring Using Principles Of Water And Energy Balance, Gabriel B. Senay, Stefanie Bohms, James P. Verdin Jan 2012

Remote Sensing Of Evapotranspiration For Operational Drought Monitoring Using Principles Of Water And Energy Balance, Gabriel B. Senay, Stefanie Bohms, James P. Verdin

United States Geological Survey: Staff Publications

Evapotranspiration (ET) is an important component of the hydrologic budget because it reflects the exchange of mass and energy between the soil–water–vegetation system and the atmosphere. Prevailing weather conditions influence potential or reference ET through variables such as radiation, temperature, wind, and relativity humidity. In addition to these weather variables, actual ET (ETa) is also affected by land cover type and condition, as well as soil moisture. The dependence of ETa on land cover and soil moisture, and its direct relationship with carbon dioxide assimilation in plants, makes it an important variable for monitoring drought, crop yield, …


On Thinning Of Chains In Mcmc, William A. Link, Mitchell J. Eaton Jan 2012

On Thinning Of Chains In Mcmc, William A. Link, Mitchell J. Eaton

United States Geological Survey: Staff Publications

1. Markov chain Monte Carlo (MCMC) is a simulation technique that has revolutionised the analysis of ecological data, allowing the fitting of complex models in a Bayesian framework. Since 2001, there have been nearly 200 papers using MCMC in publications of the Ecological Society of America and the British Ecological Society, including more than 75 in the journal Ecology and 35 in the Journal of Applied Ecology.

2. We have noted that many authors routinely ‘thin’ their simulations, discarding all but every kth sampled value; of the studies we surveyed with details on MCMC implementation, 40% reported thinning.

3. Thinning …