Internal and external scope in willingness-to-pay estimates for threatened and endangered wildlife
K.L. Giraud, J.B. Loomis, R.L. Johnson
1999, Journal of Environmental Management (56) 221-229
Economic theory suggests willingness-to-pay (WTP) should be significantly higher for a comprehensive good than for a subset of that good. We tested this using both a split sample design (external scope test) and paired responses (internal scope test) for WTP for several endangered fish and wildlife species in the US....
Exotic plant species invade hot spots of native plant diversity
T.J. Stohlgren, Dan Binkley, G.W. Chong, M. A. Kalkhan, L. D. Schell, K.A. Bull, Yuka Otsuki, G. Newman, Michael A. Bashkin, Y. Son
1999, Ecological Monographs (69) 25-46
Some theories and experimental studies suggest that areas of low plant species richness may be invaded more easily than areas of high plant species richness. We gathered nested-scale vegetation data on plant species richness, foliar cover, and frequency from 200 1-m2 subplots (20 1000-m2 modified-Whittaker plots) in the Colorado Rockies...
Elastic-wave velocity in marine sediments with gas hydrates: Effective medium modeling
M.B. Helgerud, J. Dvorkin, A. Nur, A. Sakai, T. Collett
1999, Geophysical Research Letters (26) 2021-2024
We offer a first-principle-based effective medium model for elastic-wave velocity in unconsolidated, high porosity, ocean bottom sediments containing gas hydrate. The dry sediment frame elastic constants depend on porosity, elastic moduli of the solid phase, and effective pressure. Elastic moduli of saturated sediment are calculated from...
A method for nitrate collection for δ15N and δ18O analysis from waters with low nitrate concentrations
Cecily C.Y. Chang, J. Langston, M. Riggs, K. Campbell, S. R. Silva, C. Kendall
1999, Canadian Journal of Fisheries and Aquatic Sciences (56) 1856-1864
Recently, methods have been developed to analyze NO3- for δ15N and δ18O, improving our ability to identify NO3- sources and transformations. However, none of the existing methods are suited for waters with low NO3- concentrations (0.7-10 µM). We describe an improved method for collecting and recovering NO3- on exchange columns....
Laboratory evaluation of a lake trout bioenergetics model
Charles P. Madenjian, Daniel V. O’Connor
1999, Transactions of the American Fisheries Society (128) 802-814
Lake trout Salvelinus namaycush, aged 3 and 6 years and with average weights of 700 and 2,000 g, were grown in laboratory tanks for up to 407 d under a thermal regime similar to that experienced by lake trout in nearshore Lake Michigan. Lake trout were fed alewifeAlosa pseudoharengus and rainbow smelt Osmerus...
Stasis and extinction of Silurian (Llandovery-Wenlock) trilobite associations related to oceanic cyclicity
Donald G. Mikulic, Joanne Kluessendorf
1999, Journal of Paleontology (73) 320-325
Silurian trilobites of the central United States belong to a series of temporally-successive associations which appeared abruptly, maintained taxonomic stasis for a time, and then disappeared abruptly. Their disappearance resulted from global perturbations of short-term duration and moderate magnitude, which caused substantial taxonomic replacement but no reorganization of major ecosystems....
Estimation of near-surface shear-wave velocity by inversion of Rayleigh waves
J. Xia, R. D. Miller, C.B. Park
1999, Geophysics (64) 691-700
The shear‐wave (S-wave) velocity of near‐surface materials (soil, rocks, pavement) and its effect on seismic‐wave propagation are of fundamental interest in many groundwater, engineering, and environmental studies. Rayleigh‐wave phase velocity of a layered‐earth model is a function of frequency and four groups...
Development of a comprehensive watershed model applied to study stream yield under drought conditions
S.P. Perkins, M. Sophocleous
1999, Groundwater (37) 418-426
We developed a model code to simulate a watershed's hydrology and the hydraulic response of an interconnected stream-aquifer system, and applied the model code to the Lower Republican River Basin in Kansas. The model code links two well-known computer programs: MODFLOW (modular 3-D flow...
Decadal variations in the strength of ENSO teleconnections with precipitation in the western United States
G.J. McCabe, M. D. Dettinger
1999, International Journal of Climatology (19) 1399-1410
Changing patterns of correlations between the historical average June-November Southern Oscillation Index (SOI) and October-March precipitation totals for 84 climate divisions in the western US indicate a large amount of variability in SOI/precipitation relations on decadal time scales. Correlations of western US precipitation with SOI and other indices of tropical...
Reactive solute transport in streams: A surface complexation approach for trace metal sorption
Robert L. Runkel, Briant A. Kimball, Diane M. McKnight, Kenneth E. Bencala
1999, Water Resources Research (35) 3829-3840
A model for trace metals that considers in-stream transport, metal oxide precipitation-dissolution, and pH-dependent sorption is presented. Linkage between a surface complexation submodel and the stream transport equations provides a framework for modeling sorption onto static and/or dynamic surfaces. A static surface (e.g., an iron- oxide-coated streambed) is defined as...
The effect of temperature on experimental and natural chemical weathering rates of granitoid rocks
A. F. White, A.E. Blum, T.D. Bullen, D.V. Vivit, M. Schulz, J. Fitzpatrick
1999, Geochimica et Cosmochimica Acta (63) 3277-3291
The effects of climatic temperature variations (5-35??C) on chemical weathering are investigated both experimentally using flow-through columns containing fresh and weathered granitoid rocks and for natural granitoid weathering in watersheds based on annual solute discharge. Although experimental Na and Si effluent concentrations are significantly higher in the fresh relative to...
Soil-like deposits observed by Sojourner, the Pathfinder rover
Henry J. Moore, Donald B. Bickler, Joy A. Crisp, Howard J. Eisen, Jeffrey A. Gensler, Albert F.C. Haldemann, Jacob R. Matijevic, Lisa K. Reid, Ferenc Pavlics
1999, Journal of Geophysical Research E: Planets (104) 8729-8746
Most of the soil-like materials at the Pathfinder landing site behave like moderately dense soils on Earth with friction angles near 34°-39° and are called cloddy deposits. Cloddy deposits appear to be poorly sorted with dust-sized to granule-sized mineral or rock grains; they may contain pebbles, small rock fragments, and...
Water and sediment characteristics associated with avian botulism outbreaks in wetlands
Tonie E. Rocke, Michael D. Samuel
1999, Journal of Wildlife Management (63) 1249-1260
Avian botulism kills thousands of waterbirds annually throughout North America, but management efforts to reduce its effects have been hindered because environmental conditions that promote outbreaks are poorly understood. We measured sediment and water variables in 32 pairs of wetlands with and without a current outbreak of avian botulism. Wetlands...
Applications and issues of GIS as tool for civil engineering modeling
S.B. Miles, C.L. Ho
1999, Journal of Computing in Civil Engineering (13) 144-152
A tool that has proliferated within civil engineering in recent years is geographic information systems (GIS). The goal of a tool is to supplement ability and knowledge that already exists, not to serve as a replacement for that which is lacking. To secure the benefits and avoid misuse of a...
Chlorine-bearing amphiboles from the Fraser mine, Sudbury, Ontario, Canada: Description and crystal chemistry
K.A. McCormick, A.M. McDonald
1999, Canadian Mineralogist (37) 1385-1403
Three chemically distinct populations of Cl-bearing amphibole have been recognized in association with contact Ni-Cu ore deposits in Footwall Breccia at the Fraser mine, Sudbury, Ontario. The first population, defined as halogen-poor (<0.5 wt.% Cl) actinolite and magnesiohornblende, occurs predominantly as pale green grains and cores. These are generally overgrown...
Aeromagnetic legacy of early Paleozoic subduction along the Pacific margin of Gondwana
Carol A. Finn, D. Moore, D. Damaske, T. Mackey
1999, Geology (27) 1087-1090
Comparison of the aeromagnetic signatures and geology of southeastern Australia and northern Victoria Land, Antarctica, with similar data from ancient subduction zones in California and Japan, provides a framework for reinterpretation of the plate tectonic setting of the Pacific margin of early Paleozoic Gondwana. In our model, the plutons in...
Estimates of runoff using water-balance and atmospheric general circulation models
D.M. Wolock, G.J. McCabe
1999, Conference Paper, Journal of the American Water Resources Association
The effects of potential climate change on mean annual runoff in the conterminous United States (U.S.) are examined using a simple water-balance model and output from two atmospheric general circulation models (GCMs). The two GCMs are from the Canadian Centre for Climate Prediction and Analysis (CCC) and the Hadley Centre...
The types of data needed for assessing the environmental and human health impacts of coal
R. B. Finkelman, P.M.K. Gross
1999, International Journal of Coal Geology (40) 91-101
Coal is one of the most important sources of energy. Its worldwide use will continue to expand during the next several decades, particularly in rapidly developing countries such as China and India. Unfortunately, coal use may bring with it environmental and human health costs. Many of the environmental and health...
Spectroscopic confirmation of uranium(VI)-carbonato adsorption complexes on hematite
John R. Bargar, Rebecca Reitmeyer, James A. Davis
1999, Environmental Science & Technology (33) 2481-2484
Evaluating societal risks posed by uranium contamination from waste management facilities, mining sites, and heavy industry requires knowledge about uranium transport in groundwater, often the most significant pathway of exposure to humans. It has been proposed that uranium mobility in aquifers may be controlled by adsorption of U(VI)−carbonato complexes on...
Effects of spatial grouping on the functional response of predators
C. Cosner, D.L. DeAngelis, J.S. Ault, D.B. Olson
1999, Theoretical Population Biology (56) 65-75
A unified mechanistic approach is given for the derivation of various forms of functional response in predator-prey models. The derivation is based on the principle-of-mass action but with the crucial refinement that the nature of the spatial distribution of predators and/or opportunities for predation are taken into account in an...
SAR studies in the Yuma Desert, Arizona: Sand penetration, geology, and the detection of military ordnance debris
G. G. Schaber
1999, Remote Sensing of Environment (67) 320-347
Synthetic Aperture Radar (SAR) images acquired over part of the Yuma Desert in southwestern Arizona demonstrate the ability of C-band (5.7-cm wavelength), L-band (24.5 cm), and P-band (68 cm) AIRSAR signals to backscatter from increasingly greater depths reaching several meters in blow sand and sandy alluvium. AIRSAR images obtained within...
Petrology and geochemistry of late-stage intrusions of the A-type, mid-Proterozoic Pikes Peak batholith (Central Colorado, USA): Implications for petrogenetic models
D. R. Smith, J. Noblett, R. A. Wobus, D. Unruh, J. Douglass, R. Beane, C. Davis, S. Goldman, G. Kay, B. Gustavson, B. Saltoun, J. Stewart
1999, Precambrian Research (98) 271-305
The ~1.08 Ga anorogenic, A-type Pikes Peak batholith (Front Range, central Colorado) is dominated by coarse-grained, biotite ?? amphibole syenogranites and minor monzogranites, collectively referred to as Pikes Peak granite (PPG). The batholith is also host to numerous small, late-stage plutons that have been subdivided into two groups (e.g. Wobus,...
Stress drop for three M∼4.3-4.7 (1992-1994) Parkfield, CA, earthquakes
Joe B. Fletcher, Mariagiovanna Guatteri
1999, Geophysical Research Letters (26) 2295-2298
In a previous paper (Fletcher and Spudich, 1998) we determined the slip distribution for the three M∼4.3 to 4.7 Parkfield events that occurred between Oct. 20, 1992 and Dec. 20, 1994. The rupture characteristics of these events are of particular interest because they are the largest events to occur at...
The strain in the array is mainly in the plane (waves below ~1 Hz)
J. Gomberg, G. Pavlis, P. Bodin
1999, Bulletin of the Seismological Society of America (89) 1428-1438
We compare geodetic and single-station methods of measuring dynamic deformations and characterize their causes in the frequency bands 0.5-1.0 Hz and 4.0-8.0 Hz. The geodetic approach utilizes data from small-aperture seismic arrays, applying techniques from geodesy. It requires relatively few assumptions and a priori information....
Negative pH, efflorescent mineralogy, and consequences for environmental restoration at the iron mountain superfund site, California
D. Kirk Nordstrom, Charles N. Alpers
1999, Proceedings of the National Academy of Sciences of the United States of America (96) 3455-3462
The Richmond Mine of the Iron Mountain copper deposit contains some of the most acid mine waters ever reported. Values of pH have been measured as low as -3.6, combined metal concentrations as high as 200 g/liter, and sulfate concentrations as high as 760 g/liter. Copious quantities of soluble metal...
