Automated calibration of a stream solute transport model: Implications for interpretation of biogeochemical parameters
D.T. Scott, M.N. Gooseff, K.E. Bencala, R.L. Runkel
2003, Journal of the North American Benthological Society (22) 492-510
The hydrologic processes of advection, dispersion, and transient storage are the primary physical mechanisms affecting solute transport in streams. The estimation of parameters for a conservative solute transport model is an essential step to characterize transient storage and other physical features that cannot be directly measured, and often is a...
A gentle introduction to quantile regression for ecologists
B.S. Cade, B.R. Noon
2003, Frontiers in Ecology and the Environment (1) 412-420
Quantile regression is a way to estimate the conditional quantiles of a response variable distribution in the linear model that provides a more complete view of possible causal relationships between variables in ecological processes. Typically, all the factors that affect ecological processes are not measured and included in the statistical...
Non-native plant invasions in managed and protected ponderosa pine/Douglas-fir forests of the Colorado Front Range
Paula J. Fornwalt, M. R. Kaufmann, L. S. Huckaby, J. M. Stoker, Thomas J. Stohlgren
2003, Forest Ecology and Management (177) 515-527
We examined patterns of non-native plant diversity in protected and managed ponderosa pine/Douglas-fir forests of the Colorado Front Range. Cheesman Lake, a protected landscape, and Turkey Creek, a managed landscape, appear to have had similar natural disturbance histories prior to European settlement and fire protection during the last century....
Dynamics of peat accumulation and marl flat formation in a calcareous fen, midwestern United States
J.J. Miner, D.B. Ketterling
2003, Wetlands (23) 950-960
The age and sequence of peat accumulation were investigated at a calcareous fen in northeastern Illinois, USA. The purpose of this study was to identify the processes that form and sustain marl flats, which are areas of marl or tufa substrate within the fen that contain numerous rare plant species....
Quantitative characterization of the regressive ecological succession by fractal analysis of plant spatial patterns
C.L. Alados, Y. Pueyo, M.L. Giner, T. Navarro, J. Escos, F. Barroso, B. Cabezudo, J.M. Emlen
2003, Ecological Modelling (163) 1-17
We studied the effect of grazing on the degree of regression of successional vegetation dynamic in a semi-arid Mediterranean matorral. We quantified the spatial distribution patterns of the vegetation by fractal analyses, using the fractal information dimension and spatial autocorrelation measured by detrended fluctuation analyses (DFA). It is the first...
Aftershocks and triggered events of the Great 1906 California earthquake
A.J. Meltzner, D.J. Wald
2003, Bulletin of the Seismological Society of America (93) 2160-2186
The San Andreas fault is the longest fault in California and one of the longest strike-slip faults in the world, yet little is known about the aftershocks following the most recent great event on the San Andreas, the Mw 7.8 San Francisco earthquake on 18 April 1906. We conducted a...
The dependence of PGA and PGV on distance and magnitude inferred from Northern California ShakeMap data
J. Boatwright, H. Bundock, J. Luetgert, L. Seekins, L. Gee, P. Lombard
2003, Bulletin of the Seismological Society of America (93) 2043-2055
We analyze peak ground velocity (PGV) and peak ground acceleration (PGA) data from 95 moderate (3.5 ??? M < 5.5) and 9 large (5.5 ??? M ??? 7.1) earthquakes in northern California. The 95 moderate earthquakes occurred from August 1998 through December 2002, and their peak motions were compiled and...
Simulation of Submarine Ground Water Discharge to a Marine Estuary: Biscayne Bay, Florida
C.D. Langevin
2003, Ground Water (41) 758-771
Variable density ground water flow models are rarely used to estimate submarine ground water discharge because of limitations in computer speed, data availability, and availability of a simulation tool that can minimize numerical dispersion. This paper presents an application of the SEAWAT code, which is a combined version of MODFLOW...
Effects of daily precipitation and evapotranspiration patterns on flow and VOC transport to groundwater along a watershed flow path
Richard L. Johnson, R.B. Thoms, J.S. Zogorski
2003, Environmental Science & Technology (37) 4944-4954
MTBE and other volatile organic compounds (VOCs) are widely observed in shallow groundwater in the United States, especially in urban areas. Previous studies suggest that the atmosphere and/or nonpoint surficial sources could be responsible for some of those VOCs, especially in areas where there is net recharge to groundwater. However,...
The geochemical evolution of riparian ground water in a forested piedmont catchment
Douglas A. Burns, Niel Plummer, Jeffrey J. McDonnell, Eurybiades Busenberg, Gerolamo C. Casile, Carol Kendall, Richard P. Hooper, James E. Freer, Norman E. Peters, Keith Beven, Peter Schlosser
2003, Groundwater (41) 913-925
The principal weathering reactions and their rates in riparian ground water were determined at the Panola Mountain Research Watershed (PMRW) near Atlanta, Georgia. Concentrations of major solutes were measured in ground water samples from 19 shallow wells completed in the riparian (saprolite) aquifer and in one borehole completed in granite,...
Polybaric evolution of phonolite, trachyte, and rhyolite volcanoes in eastern Marie Byrd Land, Antarctica: Controls on peralkalinity and silica saturation
W.E. LeMasurier, K. Futa, M. Hole, Y. Kawachi
2003, International Geology Review (45) 1055-1099
In the Marie Byrd Land volcanic province, peralkaline and metaluminous trachytes, phonolites, and rhyolites occur in 18 large shield volcanoes that are closely associated in time and space. They are arrayed radially across an 800 km wide structural dome, with the oldest at the crest and the youngest around the flanks. Several lines of evidence suggest that these rocks evolved via...
Two-dimensional inverse and three-dimensional forward modeling of MT (magnetotelluric) data to evaluate the mineral potential of the Amphitheater Mountains, Alaska, USA
Louise Pellerin, Jeanine M. Schmidt, G. Michael Hoversten
2003, Conference Paper, Proceedings of the 3DEM-3 symposium: Three dimensional electromagnetics III: ASEG Special Publications 2003(1)
As part of an integrated geological and geophysical study to assess the mineral potential in the Amphitheater Mountains of south-central Alaska, USA, two magnetotelluric (MT) profiles were acquired during the summer of 2002. The two parallel MT lines, along with helicopter electromagnetic (HEM) and magnetic data acquired by the State...
Sediment dynamics drive contaminant dynamics
David H. Schoellhamer, Gregory Shellenbarger, Neil K. Ganju, Jay A. Davis, Lester J. McKee
2003, Pulse of the Estuary 2003
Many contaminants of greatest concern in San Francisco Bay, including mercury and PCBs, are primarily associated with sediment particles rather than dissolved in water. Therefore, the movement and fate of sediment determines the movement and fate of many contaminants in the Bay. Because of this close association, the RMP monitors...
Estimating mortality rates of adult fish from entrainment through the propellers of river towboats
S. Gutreuter, John M. Dettmers, David H. Wahl
2003, Transactions of the American Fisheries Society (132) 646-661
We developed a method to estimate mortality rates of adult fish caused by entrainment through the propellers of commercial towboats operating in river channels. The method combines trawling while following towboats (to recover a fraction of the kills) and application of a hydrodynamic model of diffusion (to estimate the fraction...
Effects of spatial and temporal variability of turbidity on phytoplankton blooms
Christine L. May, Jeffrey R. Koseff, Lisa Lucas, James E. Cloern, David H. Schoellhamer
2003, Marine Ecology Progress Series (254) 111-128
A central challenge of coastal ecology is sorting out the interacting spatial and temporal components of environmental variability that combine to drive changes in phytoplankton biomass. For 2 decades, we have combined sustained observation and experimentation in South San Francisco Bay (SSFB) with numerical modeling analyses to search for general...
Electrofishing and its harmful effects on fish
Darrel E. Snyder
2003, Information and Technology Report 2003-0002
Electrofishing, a valuable sampling technique in North America for over half a century, involves a very dynamic and complex mix of physics, physiology, and behavior that remains poorly understood. New hypotheses have been advanced regarding "power transfer" to fish and the epileptic nature of their responses to electric fields, but...
Evolution of CAM and C4 carbon-concentrating mechanisms
Jon E. Keeley, Philip W. Rundel
2003, International Journal of Plant Sciences (164) 555-577
Mechanisms for concentrating carbon around the Rubisco enzyme, which drives the carbon-reducing steps in photosynthesis, are widespread in plants; in vascular plants they are known as crassulacean acid metabolism (CAM) and C4 photosynthesis. CAM is common in desert succulents, tropical epiphytes, and aquatic plants and is characterized by nighttime fixation...
Simulation of ground motion using the stochastic method
D.M. Boore
2003, Pure and Applied Geophysics (160) 635-676
A simple and powerful method for simulating ground motions is to combine parametric or functional descriptions of the ground motion's amplitude spectrum with a random phase spectrum modified such that the motion is distributed over a duration related to the earthquake magnitude and to the distance from the source. This...
Why earthquakes correlate weakly with the solid Earth tides: Effects of periodic stress on the rate and probability of earthquake occurrence
N.M. Beeler, D.A. Lockner
2003, Journal of Geophysical Research B: Solid Earth (108)
We provide an explanation why earthquake occurrence does not correlate well with the daily solid Earth tides. The explanation is derived from analysis of laboratory experiments in which faults are loaded to quasiperiodic failure by the combined action of a constant stressing rate, intended to simulate tectonic loading, and a...
Tag loss can bias Jolly-Seber capture-recapture estimates
T. L. McDonald, Steven C. Amstrup, B.F.J. Manly
2003, Wildlife Society Bulletin (31) 814-822
We identified cases where the Jolly-Seber estimator of population size is biased under tag loss and tag-induced mortality by examining the mathematical arguments and performing computer simulations. We found that, except under certain tag-loss models and high sample sizes, the population size estimators (uncorrected for tag loss) are severely biased...
Uptake of elements from seawater by ferromanganese crusts: Solid-phase associations and seawater speciation
A. Koschinsky, J.R. Hein
2003, Marine Geology (198) 331-351
Marine Fe-Mn oxyhydroxide crusts form by precipitation of dissolved components from seawater. Three hydrogenetic crust samples (one phosphatized) and two hydrothermal Mn-oxide samples were subjected to a sequential-leaching procedure in order to determine the host phases of 40 elements. Those host-phase associations are discussed with respect to element speciation in...
Paleolimnology of Lake Tanganyika, East Africa, over the past 100 k yr
C.A. Scholz, J.W. King, G.S. Ellis, Peter K. Swart, J.C. Stager, Steven M. Colman
2003, Conference Paper, Journal of Paleolimnology
New sediment core data from a unique slow-sedimentation rate site in Lake Tanganyika contain a much longer and continuous record of limnological response to climate change than have been previously observed in equatorial regions of central Africa. The new core site was first located through an extensive seismic reflection survey...
Ecohydrology of a resource-conserving semiarid woodland: Effects of scale and disturbance
B.P. Wilcox, D.D. Breshears, Craig D. Allen
2003, Ecological Monographs (73) 223-239
In semiarid landscapes, the linkage between runoff and vegetation is a particularly close one. In this paper we report on the results of a long-term and multiple-scale study of interactions between runoff, erosion, and vegetation in a piñon–juniper woodland in New Mexico. We use our results to address three...
Environmental Resources Analysis System, A Prototype DSS
M. Flug, S.G. Campbell
P. Bizier, P. DeBarry, editor(s)
2003, Conference Paper, World Water and Environmental Resources Congress
Since the 1960's, an increase in the public's environmental ethics, federal species preservation, water quality protection, and interest in free flowing rivers have evolved to the current concern for stewardship and conservation of natural resources. This heightened environmental awareness creates an appetite for data, models, information management, and systematic analysis...
U.S. Geological Survey Greater Everglades Science Program: 2002 Biennial Report
Arturo E. Torres, Aaron L. Higer, Heather S. Henkel, Patsy R. Mixson, Jane R. Eggleston, Teresa L. Embry, Gail Clement
2003, Open-File Report 03-54
IntroductionThe U.S. Geological Survey (USGS) conducts scientific investigations in south Florida to improve society’s understanding of the environment and assist in the sustainable use, protection, and restoration of the Everglades and other ecosystems within the region. The investigations summarized in this document have been carried out under the Greater Everglades...
