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Articles 3331 - 3360 of 3635

Full-Text Articles in Other Environmental Sciences

Body Mass Patterns Predict Invasions And Extinctions In Transforming Landscapes, Craig R. Allen, Elizabeth A. Forys, C. S. Holling Jan 1999

Body Mass Patterns Predict Invasions And Extinctions In Transforming Landscapes, Craig R. Allen, Elizabeth A. Forys, C. S. Holling

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Scale-specific patterns of resource distribution on landscapes entrain attributes of resident animal communities such that species body-mass distributions are organized into distinct aggregations. Species within each aggregation respond to resources over the same range of scale. This discontinuous pattern has predictive power: invasive species and extinct or declining species in landscapes subject to human transformation tend to be located at the edge of body-mass aggregations (P < 0.01), which may be transition zones between distinct ranges of scale. Location at scale breaks affords species great opportunity, but also potential crisis.

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Development And Evaluation Of A Standard Weight (WS) Equation For Blue Catfish, Maurice I. Muoneke, Kevin L. Pope Jan 1999

Development And Evaluation Of A Standard Weight (WS) Equation For Blue Catfish, Maurice I. Muoneke, Kevin L. Pope

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

Using a data set composed of 33 populations from six states, we employed the regression-linepercentile technique to develop a standard weight equation for blue catfish Ictalurus furcatus and validated it with an independent data set composed of 43 populations from 10 states. The equation is log10Ws=-6.067+ 3.400 log10TL, where Ws is standard weight in grams and TL is total length in millimeters. The English-unit equivalent (pounds and inches) is log10Ws=-3.950+ 3.400 log10TL. The equation is valid for blue catfish 160 mm (approximately 6 in) TL and longer. …

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Comparison Of An Enzyme-Linked Immunosorbent Assay (Elisa) To Gas Chromatography (Gc) - Measurement Of Polychlorinated Biphenyls (Pcbs) In Selected Us Fish Extracts, James L. Zajicek, Donald E. Tillitt, Ted R. Schwartz, Christopher J. Schmitt, Robert O. Harrison Jan 1999

Comparison Of An Enzyme-Linked Immunosorbent Assay (Elisa) To Gas Chromatography (Gc) - Measurement Of Polychlorinated Biphenyls (Pcbs) In Selected Us Fish Extracts, James L. Zajicek, Donald E. Tillitt, Ted R. Schwartz, Christopher J. Schmitt, Robert O. Harrison

United States Geological Survey: Staff Publications

The analysis of PCBs in fish tissues by immunoassay methods was evaluated using fish collected from a US monitoring program, the National Contaminant Biomonitoring Program of the US Department of Interior, Fish and Wildlife Service. Selected composite whole fish samples, which represented widely varying concentrations and sources of PCBs, were extracted and subjected to congener PCB analysis by gas chromatography (GC) and total PCB analysis using an ELISA (ePCBs) calibrated against technical Aroclor 1248. PCB congener patterns in these fishes were different from the patterns found in commercial Aroclors or their combinations as demonstrated by principal component analysis of normalized …

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200,000 Years Of Climate Change Recorded In Eolian Sediments Of The High Plains Of Eastern Colorado And Western Nebraska, Daniel R. Muhs, James Swinehart, David Loope, John N. Aleinikoff, Josh Been Jan 1999

200,000 Years Of Climate Change Recorded In Eolian Sediments Of The High Plains Of Eastern Colorado And Western Nebraska, Daniel R. Muhs, James Swinehart, David Loope, John N. Aleinikoff, Josh Been

United States Geological Survey: Staff Publications

Loess and eolian sand cover vast areas of the western Great Plains of Nebraska, Kansas and Colorado (Fig. 1). In recent studies of Quaternary climate change, there has been a renewed interest in loess and eolian sand. Much of the attention now given to loess stems from new studies of long loess sequences that contain detailed records of Quaternary glacial-interglacial cycles, thought to be a terrestrial equivalent to the foraminiferal oxygen isotope record in deep-sea sediments (Fig. 2). Loess is also a direct record of atmospheric circulation, and identification of loess paleowinds in the geologic record can test atmospheric general …

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Factors Affecting The Movements Of Rainbow Trout (Oncorhynchus Mykiss) In Lake Ogallala, Nebraska, Tadd M. Barrow Dec 1998

Factors Affecting The Movements Of Rainbow Trout (Oncorhynchus Mykiss) In Lake Ogallala, Nebraska, Tadd M. Barrow

School of Natural Resources: Dissertations, Theses, and Student Research

No abstract provided.

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Climate Change And Nebraska Sep 1998

Climate Change And Nebraska

United States Environmental Protection Agency: Publications

The earth's climate is predicted to change because human activities are altering the chemical composition of the atmosphere through the buildup of greenhouse gases - primarily carbon dioxide, methane, nitrous oxide, and chlorofluorocarbons. The heat-trapping property of these greenhouse gases is undisputed. Although there is uncertainty about exactly how and when the earth's climate will respond to enhanced concentrations of greenhouse gases, observations indicate that detectable changes are under way. There most likely will be increases in temperature and changes in precipitation, soil moisture, and sea level, which could have adverse effects on many ecological systems, as well as on …

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Birds And Agroecological Relationships In Organic And Non-Organic Farmland, Nancy A. Beecher Aug 1998

Birds And Agroecological Relationships In Organic And Non-Organic Farmland, Nancy A. Beecher

School of Natural Resources: Dissertations, Theses, and Student Research

No abstract provided.

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Landowner And Tourist Attitudes Toward Elk Management In The Pine Ridge Region Of Northwestern Nebraska, R. Daniel Crank May 1998

Landowner And Tourist Attitudes Toward Elk Management In The Pine Ridge Region Of Northwestern Nebraska, R. Daniel Crank

School of Natural Resources: Dissertations, Theses, and Student Research

No abstract provided.

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Influence Of Buffer Strip Width And Composition In Reduction Of Agricultural Non-Point Source Contaminants, Tim Schmitt May 1998

Influence Of Buffer Strip Width And Composition In Reduction Of Agricultural Non-Point Source Contaminants, Tim Schmitt

School of Natural Resources: Dissertations, Theses, and Student Research

No abstract provided.

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Relationship Between Ecosystem Productivity And Photosynthetically Active Radiation For Northern Peatlands, S. E. Frolkin, J.L. Bubier, T.R. Moore, T. Ball, L.M. Bellisario, A. Bhardwaj, P. Carroll, P.M. Crill, Peter M. Lafleur, J.H. Mccaughey, N.T. Roulet, A. E. Suyker, S.B. Verma, J.M. Waddington, G.J. Whiting Mar 1998

Relationship Between Ecosystem Productivity And Photosynthetically Active Radiation For Northern Peatlands, S. E. Frolkin, J.L. Bubier, T.R. Moore, T. Ball, L.M. Bellisario, A. Bhardwaj, P. Carroll, P.M. Crill, Peter M. Lafleur, J.H. Mccaughey, N.T. Roulet, A. E. Suyker, S.B. Verma, J.M. Waddington, G.J. Whiting

School of Natural Resources: Faculty Publications

We analyzed the relationship between new ecosystem exchange of carbon dioxide (NEE) and irradiance (as photosynthetic photon flux density of PPFD), using published and unpublished data that have been collected during midgrowing season for carbon balance studies at seven peatlands in North America and Europe. NEE measurements included both eddy-correlation tower and clear, static chamber methods, which gave very similar results. Data were analyzed by site, as aggregated data set for all peatland type (bog, poor fen, rich fen, and all fens) and as a single aggregated data set for all peatlands. In all cases, a fit with a rectangular …

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Air Temperature Variations And Rice Productivity In Bangladesh: A Comparative Study Of The Performance Of The Yield And The Ceres-Rice Models, Rezaul Mahmood Mar 1998

Air Temperature Variations And Rice Productivity In Bangladesh: A Comparative Study Of The Performance Of The Yield And The Ceres-Rice Models, Rezaul Mahmood

School of Natural Resources: Faculty Publications

Potential increase in air temperature due to climatic change and inter-annual climatic variability and its impacts on crop productivity is of major concern to crop scientists. A number of physically-based models have been developed and applied to estimate crop–environment relationships. In the present study the performance of two such models (the YIELD and the CERES-Rice) are discussed. These two models are used to estimate boro rice productivity under normal and abnormal climate scenarios in Bangladesh. This study finds that boro rice productivity at Mymensingh predicted by the YIELD is higher than the prediction by the CERES-Rice. Productivity estimates for Barisal …

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Climatology Of The Daily Temperature Range Annual Cycle In The United States, Daniel J. Leathers, Michael A. Palecki, David A. Robinson, Kenneth F. Dewey Feb 1998

Climatology Of The Daily Temperature Range Annual Cycle In The United States, Daniel J. Leathers, Michael A. Palecki, David A. Robinson, Kenneth F. Dewey

School of Natural Resources: Faculty Publications

Many researchers are presently interested in detecting long-term trends in annual or seasonal daily temperature range (DTR), and attributing these changes to anthropogenic origins. However, very little work has been done to confirm the mechanisms that are important to determining the long-term average annual cycle of the DTR. Therefore, the focus of this work is to examine the spatial and temporal difference in the DTR average annual cycle across the United States, and to associate the patterns of these cycles with potential causal variables. Three major types of DTR annual cycle exist in the United States: high sun season maximum …

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Optical Properties Of Canopy Elements In Black Spruce, Jack Pine And Aspen Stands In Saskatchewan, Canada, Elizabeth A. Walter-Shea, Mark A. Mesarch Jan 1998

Optical Properties Of Canopy Elements In Black Spruce, Jack Pine And Aspen Stands In Saskatchewan, Canada, Elizabeth A. Walter-Shea, Mark A. Mesarch

School of Natural Resources: Faculty Publications

No abstract provided.

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Unique Frontal Sinuses In Fossil And Living Hyaenidae (Mammalia, Carnivora): Description And Interpretation, R.M. Joeckel Jan 1998

Unique Frontal Sinuses In Fossil And Living Hyaenidae (Mammalia, Carnivora): Description And Interpretation, R.M. Joeckel

School of Natural Resources: Faculty Publications

No abstract provided.

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Characterization And Improvement Of Eos Land Products Using Measurements At Ameriflux Grassland And Wheat Sites In The Arm/Cart Region: Research Annual Performance Report For Period March 1, 1998- January 8, 1999, E. A. Walter-Shea, S. B. Verma Jan 1998

Characterization And Improvement Of Eos Land Products Using Measurements At Ameriflux Grassland And Wheat Sites In The Arm/Cart Region: Research Annual Performance Report For Period March 1, 1998- January 8, 1999, E. A. Walter-Shea, S. B. Verma

School of Natural Resources: Documents and Reviews

No abstract provided.

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An Evaluation Of Methods For Identifying And Interpreting Buried Soils In Late Quaternary Loess In Alaska, Daniel R. Muhs, Thomas A. Ager, Josh M. Been, Joseph G. Rosenbaum, Richard L. Reynolds Jan 1998

An Evaluation Of Methods For Identifying And Interpreting Buried Soils In Late Quaternary Loess In Alaska, Daniel R. Muhs, Thomas A. Ager, Josh M. Been, Joseph G. Rosenbaum, Richard L. Reynolds

United States Geological Survey: Staff Publications

The presence of buried soils in Alaskan loess is controversial, and therefore criteria for identifying buried soils in these deposits need to be evaluated. In this paper, morphologic and chemical criteria for identifying buried soils are evaluated by studying modern soils developed mostly in Holocene loess under tundra, boreal forest, and transitional coastal-boreal forest vegetation in different parts of Alaska. Data from modern Alaskan soils that developed under vegetation similar to that of the present indicate that soil morphology, organic-matter concentrations, and P concentrations can be useful diagnostic tools for identifying buried soils. Soil morphologic criteria, particularly horizon colors and …

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Earlj Life Historj And Recruitment Of Black Crappie (Pomoxis Nigromaculatus) In Two South Dakota Waters, K. L. Pope, D. W. Willis Jan 1998

Earlj Life Historj And Recruitment Of Black Crappie (Pomoxis Nigromaculatus) In Two South Dakota Waters, K. L. Pope, D. W. Willis

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

We compared the early life history of black crappie (Pomoxis nigromaculatus) in Richmond (an impoundment) and Brant (a natural lake) lakes during 1994-1996. We expected variable recruitment (i.e., missing year classes) in the natural lake and more consistent recruitment in the impoundment. Larval black crappie abundance was always higher in Richmond Lake than Brant Lake. Peak abundance of larval black crappie was highest during 1994 in both waters. However, peak larval abundance did not correspond with fall trap-net catch per unit effort (CPUE) of age-0 black crappie, which was highest during 1995. Thus, recruitment of black crappie was …

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Ecological Resilience, Biodiversity, And Scale, Garry D. Peterson, Craig R. Allen, C. S. Holling Jan 1998

Ecological Resilience, Biodiversity, And Scale, Garry D. Peterson, Craig R. Allen, C. S. Holling

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

We describe existing models of the relationship between species diversity and ecological function, and propose a conceptual model that relates species richness, ecological resilience, and scale.We suggest that species interact with scale-dependent sets of ecological structures and processes that determine functional opportunities. We propose that ecological resilience is generated by diverse, but overlapping, function within a scale and by apparently redundant species that operate at different scales, thereby reinforcing function across scales. The distribution of functional diversity within and across scales enables regeneration and renewal to occur following ecological disruption over a wide range of scales.

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Larval Black Crappie Distribution: Implications For Sampling Impoundments And Natural Lakes, Kevin L. Pope, David W. Willis Jan 1998

Larval Black Crappie Distribution: Implications For Sampling Impoundments And Natural Lakes, Kevin L. Pope, David W. Willis

Nebraska Cooperative Fish and Wildlife Research Unit: Staff Publications

An understanding of larval fish distributions is essential for developing an appropriate sampling design to monitor larval abundances. We monitored abundance of larval black crappie Pomoxis nigromaculatus to assess spatial differences in Richmond Lake (a 336-ha impoundment) and Brant Lake (a 405-ha natural lake), South Dakota, during 1994–1996. Age-0 black crappies were collected with a 500-µm mesh ichthyoplankton trawl from fixed sites within each water body. In the impoundment, larval black crappies were collected over a longer period at the upper site than at the dam site during 1994 and 1995. In the natural lake, larval black crappie abundances were …

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Continuous Lake-Sediment Records Of Glaciation In The Sierra Nevada Between 52,600 And 12,500 14c Yr B.P., Larry Benson, Howard M. May, Ronald C. Antweiler, Terry I. Brinton, Michaele Kashgarian, Joseph P. Smoot, Steve P. Lund Jan 1998

Continuous Lake-Sediment Records Of Glaciation In The Sierra Nevada Between 52,600 And 12,500 14c Yr B.P., Larry Benson, Howard M. May, Ronald C. Antweiler, Terry I. Brinton, Michaele Kashgarian, Joseph P. Smoot, Steve P. Lund

United States Geological Survey: Staff Publications

The chemistry of the carbonate-free clay-size fraction of Owens Lake sediments supports the use of total organic carbon and magnetic susceptibility as indicators of stadial-interstadial oscillations, Owens Lake records of total organic carbon, magnetic susceptibility, and chemical composition of the carbonate-free, clay-size fraction indicate that Tioga glaciation began ~24,500 and ended by ~13,600 14C yr B.P. Many of the components of glacial rock flour (e.g., TiO2 , MnO, BaO) found in Owens Lake sediments achieved maximum values during the Tioga glaciation when valley glaciers reached their greatest extent. Total organic carbon and Si02 (amorphous) concentrations reached minimum values …

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Early Life History Stages Of Gulf Sturgeon In The Suwannee River, Florida, Kenneth J. Sulak, James P. Clugston Jan 1998

Early Life History Stages Of Gulf Sturgeon In The Suwannee River, Florida, Kenneth J. Sulak, James P. Clugston

United States Geological Survey: Staff Publications

Egg sampling confirmed that Suwannee River Gulf sturgeon Acipenser ozyrinchus desotoi, a subspecies of Atlantic sturgeon A. o. oxyrinchus use the same spawning site at river kilometer (rkm) 215 from the mouth of the river each year. Forty-nine eggs were recorded in 1995, and 368 were recorded in 1996. Spawning began 4-7 d after the March new moon in both years and lasted 10-11 d; in 1996, a second 10-d spawning round began on the April new moon. Developmental synchrony among eggs recovered suggested serval discrete spawning events in both years. Total eggs deposited for three 1996 sampling days …

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Biology Of Shovelnose Sturgeon, Scaphirhynchus Platorynchus, In The Lower Platte River, Nebraska, Robin L. Hofpar Aug 1997

Biology Of Shovelnose Sturgeon, Scaphirhynchus Platorynchus, In The Lower Platte River, Nebraska, Robin L. Hofpar

School of Natural Resources: Dissertations, Theses, and Student Research

No abstract provided.

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Effects Of Spatial Resolution And Landscape Structure On Land Cover Characterization, Wenli Yang Jul 1997

Effects Of Spatial Resolution And Landscape Structure On Land Cover Characterization, Wenli Yang

Department of Geography: Dissertations, Theses, and Student Research

This dissertation addressed problems in scaling, problems that are among the main challenges in remote sensing. The principal objective of the research was to investigate the effects of changing spatial scale on the representation of land cover. A second objective was to determine the relationship between such effects, characteristics of landscape structure and scaling procedures. Four research issues related to spatial scaling were examined. They included: 1) the upscaling of Normalized Difference Vegetation Index (NDVI); 2) the effects of spatial scale on indices of landscape structure; 3) the representation of land cover databases at different spatial scales; and 4) the …

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Integrating Agroforestry Into Usda Programs: A Task Force Report To The Usda Interagency Working Group On Agroforestry, W. J. Rietveld, James P. Lassoie, Charles A. Francis, William Farris, Catalino Blanche, Bruce Wight May 1997

Integrating Agroforestry Into Usda Programs: A Task Force Report To The Usda Interagency Working Group On Agroforestry, W. J. Rietveld, James P. Lassoie, Charles A. Francis, William Farris, Catalino Blanche, Bruce Wight

United States Department of Agriculture, Forest Service / University of Nebraska-Lincoln: Faculty Publications

The task force collected and synthesized infonnation and recommended actions to develop the potential of agroforestry to help attain USDA sustainable development goals.

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Effects Of Ultraviolet Radiation On Attached Diatom Growth And Distribution, Heather Lynn Emsley Hatsell May 1997

Effects Of Ultraviolet Radiation On Attached Diatom Growth And Distribution, Heather Lynn Emsley Hatsell

School of Natural Resources: Dissertations, Theses, and Student Research

No abstract provided.

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Impacts Of Air Temperature Variations On The Boro Rice Phenology In Bangladesh: Implications For Irrigation Requirements, Rezaul Mahmood Apr 1997

Impacts Of Air Temperature Variations On The Boro Rice Phenology In Bangladesh: Implications For Irrigation Requirements, Rezaul Mahmood

School of Natural Resources: Faculty Publications

Air temperature significantly affects crop phenology. Numerous experiments have shown that prevailing air temperature determines the length of crop growth stages. Irrigation field requirements depend on the length of the crop growth stages. In the present study, a physically based parametric model, YIELD, has been applied to estimate the impacts of fluctuating air temperature (due to inter-annual climatic variability and global warming) on evapotranspiration water requirements and the length of growth stages of the irrigated boro rice in Bangladesh. The YIELD model is crop specific and crop-growth-stage specific which is a compromise between area-specific regression models and complex crop growth …

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Spectral Information Content Of The Boreal Forest, Elizabeth A. Walter-Shea Jan 1997

Spectral Information Content Of The Boreal Forest, Elizabeth A. Walter-Shea

School of Natural Resources: Faculty Publications

No abstract provided.

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Internal Anatomy Of The Snout And Paranasal Sinuses Of Hyaenodon (Mammalia, Creodonta), R. M. Joeckel, H.W. Bond, G.W. Kabalka Jan 1997

Internal Anatomy Of The Snout And Paranasal Sinuses Of Hyaenodon (Mammalia, Creodonta), R. M. Joeckel, H.W. Bond, G.W. Kabalka

School of Natural Resources: Faculty Publications

No abstract provided.

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Water-Balance Modeling In A Changing Environment: Reductions In Unconfined Aquifer Levels In The Area Between The Danube And Tisza Rivers In Hungary, Jozsef Szilagyi, Charles Vorosmarty Jan 1997

Water-Balance Modeling In A Changing Environment: Reductions In Unconfined Aquifer Levels In The Area Between The Danube And Tisza Rivers In Hungary, Jozsef Szilagyi, Charles Vorosmarty

School of Natural Resources: Faculty Publications

No abstract provided.

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Ecological Water Treatment System For Removal Of Phosphorus And Nitrogen From Polluted Water, Ray W. Drenner, Donald J. Day, Stacy J. Basham, J. Durward Smith, Susan I. Jensen Jan 1997

Ecological Water Treatment System For Removal Of Phosphorus And Nitrogen From Polluted Water, Ray W. Drenner, Donald J. Day, Stacy J. Basham, J. Durward Smith, Susan I. Jensen

School of Natural Resources: Faculty Publications

We propose that phosphorus and nitrogen can be removed from polluted water using an ecological water treatment system consisting of periphyton and fish. In the proposed system, polluted water flows through a series of vessels, and the nutrients are taken up by periphyton growing on porous screens. Algal-grazing fish feed on the periphyton and either assimilate or egest the nutrients in mucus-bound feces that settle from the water into a sediment trap. Both the fish and their feces can be harvested as nutrient sinks. In this study we examined the effects of an algal-grazing cichlid (Tilapia mossambica) and …

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