bluuebunny/crossref_metadata_2025 huggingface dataset:
A spectral model of the beam attenuation coefficient in the ocean and coastal areas
Authors: Voss Kenneth J.
Published: April 2010

A large set (∼ 100 data points at each wavelength) of multispectral beam attenuation, c(λ), data at nine wavelengths (440, 450, 490, 520, 535, 550, 565, 630, and 670 nm) is used to develop a spectral model of the beam attenuation coefficient. The relationship c(λ) − cW(λ) =[c(490 nm) − cW(490 nm)](1.563 − 1.149 × 10−3 λ) describes the spectral variation of c(λ) where cW(λ) is the pure water beam attenuation and λ is the wavelength in nm. From a subset of the data a relationship of chloropyll (Chl) to c(490) was found to be c(490) = 0.39 Chl0.57; however there is significant scatter in this relationship. The spectral c model was tested with independent data sets and the average percent difference of the measured to predicted values ranged from 0.4 to 5% for the different spectral bands.
The cycling of iron and manganese in the water column of Lake Sammamish, Washington
Authors: Balistrieri Laurie S. , Murray James W. , Paul Barbara
Published: April 2010

Processes controlling the distribution and mobility of Fe and Mn in Lake Sammamish, Washington, a seasonally anoxic lake, are deduced from a year‐long monthly study of physical, chemical, and biological parameters in the lake. Inventories of dissolved Mn and Fe in the bottom waters increase as the redox potential lowers with dissolved Mn inventories during stagnation being much larger than inventories of dissolved Fe. The shapes of the dissolved metal profiles indicate that dissolved Fe is supplied to the hypolimnion during stratification by diffusion of Fe(II) from the sediments into the overlying anoxic water as well as reduction of Fe oxide particles settling through the anoxic water column, while the dominant source of dissolved Mn to the anoxic bottom waters during most of the stratification period appears to be reduction of settling Mn‐oxide particles. Inventories of particulate Fe in the hypolimnion during the latter stages of stratification are significantly larger than inventories of particulate Mn. Peaks of particulate Fe and Mn occur in the water column from July through November and particulate Mn peaks always occur at shallower depths than peaks of particulate Fe. Flux calculations suggest that there is a sufficient supply of both oxygen and reduced metal to the particulate zones for metal‐oxide precipitation to occur. Thermodynamic calculations suggest that during the sulfidic phase of stagnation dissolved Fe concentrations in the very bottom waters may be controlled by FeS precipitation.
The biogeochemical cycling of trace metals in the water column of Lake Sammamish, Washington: Response to seasonally anoxic conditions
Authors: Balistrieri Laurie S. , Murray James W. , Paul Barbara
Published: April 2010

Total acid‐soluble and dissolved Cd, Co, Cr, Cu, Ni, Pb, and Zn concentrations in the water column of a seasonally anoxic lake (Lake Sammamish, Washington) were measured on a monthly basis during the course of a year. These data, in conjunction with Fe, Mn, sulfide, and nutrient data, are used to assess the biochemical processes controlling the distribution of trace metals in the lake and how the importance of these processes varies with time. Thermodynamic calculations are used to examine changes in dissolved metal speciation in the bottom waters during the year and to assess the saturation state of metal‐sulfide phases. Spatial and temporal changes in the redox conditions of the bottom waters result in increases in dissolved Co and Ni concentrations, peaks in particulate Co profiles, decreases in dissolved Cu and Cr concentrations, and significant changes in dissolved metal speciation during stagnation. The redox‐driven cycling of Fe and Mn in the hypolimnion has a dramatic effect on Co distributions, a slight effect on Ni concentrations, and virtually no effect on Cd, Cu, Cr, and Zn concentrations. Biological uptake and regeneration processes result in a correlation between Zn and silicate concentrations throughout the water column, and it appears that biological cycling may also influence the distribution of Cd. During the sulfidic phase of stagnation dissolved Cd concentrations in the bottom waters may be controlled by metal‐sulfide precipitation, Cr(VI) is probably reduced to more particle‐reactive Cr(III) and removed by settling particles, and Cu(II) is most likely reduced to Cu(I) and precipitated as a metal‐sulfide phase.
Type of suspended clay influences zooplankton response to phosphorus loading
Authors: Cuker Benjamin E. , Hudson Leon
Published: April 2010

The effects on zooplankton community structure of P loading and two different kinds of suspended sediments were tested in a small lake. Limnocorrals were used in a complete, triplicated, six‐treatment‐block design. Treatments were loading with P, kaolinitic clay (K), K+P, montmorillonitic clay (M), and M+P plus a control without additions. P fertilization caused blooms of blue‐green bacteria and resulted in reductions of the dominant copepod (Diaptomus mississippiensis) and cladocerans (Diaphanosoma brachyurum, Bosmina longirostris, and Ceriodaphnia reticulata), while causing a 5‐fold increase in rotifers (mostly Keratella cochlearis). Zooplankton in the K and K+P treatments were similar to the control, but cladoceran species other than Diaphanosoma were reduced. M was more detrimental to zooplankton than K, causing a 10‐fold decrease for all crustaceans. We attribute this in part to lower algal densities in the M treatment. Simultaneous P loading mitigated the effects of M on Diaphanosoma, rotifers, and copepods and may involve a transfer loop in which dissolved organic C adsorbed on clay becomes available to filter‐feeding zooplankton. The effects of mineral turbidity apparently cascaded up the food chain, with both kinds of clays reducing densities of Chaoborus larvae.
Importance of temperature, nitrate, and pH for phosphate release from aerobic sediments of four shallow, eutrophic lakes
Authors: Jensen Henning Skovgaard , Andersen Frede Ostergaard
Published: April 2010

Phosphorus released from aerobic sediment surfaces made up the major fraction of the total P‐load to the trophogenic zone in four shallow Danish lakes in 1987. Gross release rates were 15, 21, 33, and 100 mg P m−2 d−1(average summer values). In three of the lakes, water temperature alone explained ∼70% of the seasonal variation in sediment P release. Long‐term experiments with undisturbed sediment cores revealed that the P release was significantly influenced by temperature and NO3− in all four lakes, but by pH only in one lake when these three parameters varied within the normal seasonal range (temperature: 0°–21°C; NO3−: 0–200 µM; pH: 7.5–10.5). Q10 values for the temperature effect were between 4.1 and 6.8 in the three lakes with large proportions of Fe‐bound P in the sediment, but only 3.5 in the lake in which the P pool was relatively small. The thickness of the oxidized layer at the sediment surface varied from 3 to 15 mm and decreased when temperature increased. High NO3− concentrations increased the thickness throughout the season and accordingly sediment P release was reduced in winter and early summer. Meanwhile, in late summer when inorganic N was depleted in lake water, NO3− additions increased the P release from sediment, probably by stimulating the mineralization process.
Geochemistry of Mn and Fe in lake sediments in relation to lake acidity
Authors: Young Leah Bendell , Harvey Harold H.
Published: April 2010

Concentrations of easily reducible Mn (ER Mn, Mn oxides), easily reducible + reducible Fe (ERR Fe, Fe oxides), and alkaline extracted Mn and Fe (org Mn and Fe, organically bound) were determined in sediments of three circumneutral (CN) and four acidic lakes. Up to 80% of total sediment Fe (total = ERR + org Fe) was removed as ERR Fe in the CN vs. acidic lakes. Acidic lakes contained twice the total Fe compared to CN lakes, which was distributed equally between the ERR Fe and org Fe sediment fractions. Mn was recovered as ER Mn from all seven lakes. Two of four acidic lakes contained little ER Mn (due to the pH‐dependent decrease in particulate Mn precipitation). However, two acidic lakes contained surficial concentrations that were equivalent to CN lakes. ER Mn in sediments of acidic lakes is attributed to sediment diagenesis. Differences in ERR Fe and org Fe in sediments of acidic vs. CN lakes may be due to the pH‐induced precipitation of Fe humic complexes.
The migration behavior, fine structure, and bioluminescent activity of krill sound‐scattering layers
Authors: Greene Charles H. , Widder Edith A. , Youngbluth Marsh J. , Tamse Armando , Johnson Gary E.
Published: April 2010

High‐resolution SONAR and video techniques were used to quantify the migration behavior, fine structure, and bioluminescent activity of krill sound‐scattering layers (SSLs) in the Gulf of Maine. These SSLs were found to exhibit highly synchronous vertical migration behavior, considerable fine‐scale patchiness, and relatively high levels of stimulable bioluminescent activity. Our findings emphasize the highly variable and dynamic nature of krill distributions, a knowledge of which is essential to understanding their trophic role in marine ecosystems.
A new plankton trap for use in the collection of rocky intertidal zooplankton
Authors: Setran Aaron Carr
Published: April 2010

Intertidal energy levels historicallylight and nocturnal tidal cycles. Diurnal differences in taxon abundances suggest diurnal vertical migration. have precluded the use of conventional plankton sampling methods in rocky inshore habitats. A new sampling device (intertidal plankton trap) that exploits wave surge was used to determine the composition, distribution, and abundance patterns of zooplankton from the surf zone of a rocky shore habitat. On three separate dates, replicate traps were used to sample consecutive tides, concurrently at two locations, to assess diurnal differences in inshore zooplankton during daylight and nocturnal tidal cycles. Diurnal differences in taxon abundances suggest diurnal vertical migration.
The importance of benthic macrofauna in decomposition of microalgae in a coastal marine sediment
Authors: Andersen Frede Ostergaard , Kristensen Erik
Published: April 2010

The effectiveness of macrofauna in decomposing organic matter was studied in microcosms by adding 14C‐labeled microalgae to undisturbed sediment cores with and without fauna. The presence of benthic macrofauna stimulated release of 14CO2 only briefly during the initial phase (4 d); after 21 d the total amount of 14CO2 released was nearly equivalent with or without fauna. The first‐order decay rate constant of the added organic matter based on the rate of 14CO2 production was 0.019 d−1 with fauna and 0.020 without. The release of [14C]DOC from the sediment accounted for 4–5% of the total 14C release. Only a small fraction of the 14C added as algae was found as 14CO2 (max, 1.2%) or [14C]DOC (max, 0.7%) in the pore water at any time during the experiment. In contrast, there was a significant increase of both sediment TCO2 (total inorganic C) production (70%) and O2 uptake (17%) rates in the presence of animals. The discrepancy between the effect of macrofauna on fluxes of labeled vs. unlabeled compounds indicates that the surface deposit feeders primarily affected decomposition of old and relatively refractory sediment organic matter.
Internal pressurization and convective gas flow in some emergent freshwater macrophytes
Authors: Brix Hans , Sorrell> Brian K. , Orr Philip T.
Published: April 2010

Internal pressurization and convective through‐flow are demonstrated to be common attributes of wetland plants with cylindrical culms or linear leaves. Eight of 14 species tested produced static internal gas pressure differentials of 200–1,300 Pa relative to ambient and internal convective airflows of 0.2 to >10 cm3 min−1 culm−1, depending on species. Four species produced internal static pressure differentials of <100 Pa. Two species did not pressurize. The driving forces are gradients in temperature and water vapor between the internal gas spaces of the plants and the ambient atmosphere (thermal transpiration and humidity‐induced pressurization).

A clear diel variation in pressurization and convective flow was observed; rates were highest in the afternoon and lowest at night, responding to ambient changes in light, temperature, and humidity. The resistance to airflow at the stem‐rhizome junction was very high for some species, resulting in a low ability to convert internal pressurization into convective airflow through the rhizomes. Species with a high potential for internal pressurization and a low internal resistance to convective flow seem to have a competitive advantage over species that rely exclusively on diffusive gas transport, which allows them to grow in deeper waters.
Isotope fractionation associated with ammonium uptake by a marine bacterium
Authors: Hoch Matthew P. , Fogel Marilyn L. , Kirchman David L.
Published: April 2010

Bacteria can account for a large fraction of total NH4+ uptake in both pelagic and benthic marine environments. 15N natural abundance was examined to understand the effect of NH4 uptake by bacteria on nitrogen isotope biogeochemistry. Isotope fractionation (ε) for NH4+ uptake by the marine bacterium Vibrio harveyi changed from −4 to −27‰ when cells were grown on 23–182 µM NH4+ and then from −27 to −14‰ when the NH4+ concentration increased to 23.3 mM. Changes in fractionation correlated with a switch in the pathway of NH4+ uptake from membrane diffusion of NH3 and assimilation catalyzed by glutamate dehydrogenase at millimolar NH4+ to active ammonium transport (Amt) and assimilation catalyzed by glutamine synthetase (GS) at micromolar NH4+. This transition occurred between 0.1 and 1 mM NH4+. Within this concentration range, cellular N demand was no longer supported by Fickian diffusion of NH3 and Amt activity increased. The isotope fractionation of whole cells with the highest GS activity (ε = −4‰) and that measured for the GS‐catalyzed reaction in vitro (ε = −8%; pH = 7.1) differed by 5‰, which suggests that the GS reaction was not the rate‐limiting step during NH4+ uptake. Isotope fractionation associated with NH4+ uptake by marine bacteria appears to depend on the membrane transport mechanism and the ammonium assimilation enzymes. Depending on NH4+ concentrations, marine bacteria using NH4+ for growth may partly account for variation in the isotope composition of NH4+ and particulate organic N in the water column and sediments of marine environments.
The effect of long‐term alteration of in situ currents on the growth of Mercenaria mercenaria in the northern Gulf of Mexico
Authors: Judge Michael L. , Coen Loren D. , Heck K. L.
Published: April 2010

Water currents were experimentally manipulated for 3 months in a shallow subtidal sandflat through a series of nine channels with diverging, parallel, or converging walls (7 m long, 1.2 m high). Three treatments were chosen to bracket the ambient flow rates; vertically averaged velocities were reduced by 40%, reduced by 2%, or increased by 65%. Within the center of each channel, six Mercenaria mercenaria [shell length, 36.9±2.2 mm (mean ± 1 SD)] were placed haphazardly in 0.25‐m2 plots. Although water‐column chlorophyll a levels declined near the substratum, concentrations did not differ among channel flow treatments. Mean clam lengths increased 19% during the study, but growth rates did not differ significantly among channel flow treatments. These results suggest that the natural range of flow rates (up to 27 cm s−1), in the absence of local food depletion, does not alone alter growth of this active suspension feeder.
Plant pigment ratios from lakes sediments as indicators of recent acidification in alpine lakes
Authors: Guilizzoni Piero , Lami Andrea , Marchetto Aldo
Published: April 2010

Chromatographic and spectrophotometric analyses of plant pigments from sediment cores have long been used to assess the developmental history of trophic status and plant productivity of lakes. We explore the possibility of using an acetone extract ratio of absorbance at two wavelengths (430 and 410 nm) in sediment to reconstruct the time‐course of acidification in alpine lakes. Our data demonstrate that this easily measured ratio is closely correlated to lake‐water pH and that it can be used stratigraphically to describe past changes in lake acidity. Thus, the easily determined 430 : 410 ratio can complement stratigraphic studies of fossil diatoms, chrysophycean scales, and carbonaceous particles now used to provide important insights into the responses of sensitive lake systems to acid deposition.
Asymptotic optical attenuation
Authors: McCormick N. J.
Published: April 2010

The spectral irradiance attenuation coefficient normally varies with depth near the surface. It approaches a constant value in infinitely deep, homogeneous waters at depths below which all fluorescent or bioluminescent sources occur. The attenuation coefficient can equal the asymptotic coefficient for all depths, however, for a special surface illumination; when this equality occurs the angular dependence of the radiance does not change with depth. The attenuation coefficient for homogeneous waters of finite depth never approaches a constant, and the same is true for some examples of infinitely deep waters with spatially varying properties. A by‐product of the analysis is a demonstration of the importance of understanding the eigenvalue spectrum of the radiative transfer equation.
Seasonal variations of biogenic and anthropogenic halocarbons in seawater from a coastal site
Authors: Klick Silke
Published: April 2010

Volatile halocarbons were measured weekly throughout 13 months in seawater sampled at a station on the western coast of Sweden. Samples were taken in a macroalgal belt among the submerged thalli of the dominating brown seaweed Fucus vesiculosus and compared to those taken from a nearby jetty that extended into a shallow bay and allowed water sampling at a total depth of 3.5 m. With regard to their seasonality, at least three different groups of halocarbons could be distinguished and suggested different sources. The polybrominated substances CHBr3, CH2Br2, and CHBr2Cl showed summer maxima and winter minima, and the concentrations were generally higher in the algal belt, indicating their macroalgal origin. CH2I2 and CH2ClI showed distinct concentration maxima in spring and fall that were similar in the algal belt and at the jetty. These substances are most likely produced by planktonic organisms. Finally, airborne contaminants such as CCl4 occurred at higher concentrations in winter and decreased with increasing water temperature in summer.
Laboratory production of bromoform, methylene bromide, and methyl iodide by macroalgae and distribution in nearshore southern California waters
Authors: Manley Steven L. , Goodwin Kelly , North Wheeler J.
Published: April 2010

Production rates of bromoform (CHBr3), methylene bromide (CH2Br2), and methyl iodide (CH3I) were measured in the laboratory for 11 species of marine macroalgae. Production rates of the volatile bromomethanes extrapolated to a global scale suggest that marine macroalgae produce 2 × 1011 g Br yr−1(1 × 109 mol Br yr−1), 98% of which is bromoform. Laminarians (kelps) produce 61% of this organic Br. These calculations suggest that marine macroalgae are important in the biogeochemical cycling of Br. Seawater concentrations of CHBr3, CH2Br2, and CH3I were determined from various southern California coastal locales. High concentrations were measured in seawater from the canopy and the bottom of a dense bed of Macrocystis as compared to other sites. Surface seawater concentrations of these halomethanes showed a strong cross‐shore gradient with the highest concentration in the kelp canopy and the lowest at 5 km offshore. Seawater adjacent to decaying macroalgae on the bottom of a submarine canyon was not enriched in halomethanes relative to surface water. Water exiting a productive estuary was enriched only with CH2Br2, although two algal species that are abundant there (Ulva and Enteromorpha) showed high laboratory production rates of both CHBr3 and CH2Br2.
Sediment resuspension in Lake St. Clair
Authors: Hawley Nathan , Lesht Barry M.
Published: April 2010

Time‐series measurements of water transparency, wave conditions, and current speed were made at several different sites in Lake St. Clair during five different 1‐month periods in 1985 and 1986. Observed changes in suspended sediment concentration were modeled with a simple zero‐dimensional, spatially averaged, mass balance model in which local bottom erosion was expressed as a linear function of the bottom shear stress. Estimates of the three parameters required by the model (particle settling velocity, resuspension concentration, and background suspended material concentration) are reasonably consistent for the various data sets, suggesting that the properties of the lake bottom do not change significantly through either space or time. The modeled settling velocities agree with the observed suspended particle size data and the erosion rates are comparable to laboratory results for freshwater sediments. The results show that a simple mass flux model can be used to model local sediment resuspension events in Lake St. Clair with reasonable accuracy.
Seagrass detritus as the basis of a coastal planktonic food chain
Authors: Thresher Ronald E. , Nichols Peter D. , Gunn John S. , Bruce Barry D. , Furlani Dianne M.
Published: April 2010

While examining a relationship between the occurrence of winter storms and variations in the growth rate of larvae off Tasmania, we found several lines of evidence that suggest that the food chain supporting the larvae of the region’s dominant midwater predator is not based on phytoplankton, as we had expected, but rather on microbial decomposition of seagrass detritus. Seagrass detritus is known to be important in food webs of benthic coastal communities, but extensive utilization of buoyant seagrass detritus by planktonic microheterotrophs has not been reported. Offshore transport of seagrass detritus by storms occurs frequently and such detritus may be a common and important, but highly variable, source of production for coastal planktonic ecosystems.
Characterization of lacustrine iron sulfide particles with proton‐induced X‐ray emission
Authors: Davison W. , Grime G. W. , Woof C.
Published: April 2010

Black particles, collected by filtration (1.2‐µm pore size) from the anoxic waters of a soft‐water lake, were examined by a scanning proton microprobe which permitted quantitative elemental analysis by proton‐induced X‐ray emission (PIXE) and Rutherford backscattering (RBS). There was a uniform distribution of sulfur across the filter, but Fe, and to a lesser extent, Mn, was localized in ∼5‐µm‐diameter clusters. Elemental analysis with 1‐µm‐diameter beams revealed that the Fe clusters were mainly comprised of iron oxides. Iron sulfide material not in the Fe clusters had stoichiometric proportions of Fe1.0S0.60P0.60Ca0.24K0.14. Although a purely biogenic origin for P, Ca, and K cannot be ruled out, the composition is consistent with the particles originating as authigenic iron oxides which react with sulfide as they sink through the water column. The iron sulfide particles are richer in Cu (4,000 ppm) and Zn (6,000 ppm) than the iron oxides, suggesting that these elements are also concentrated as their insoluble sulfides. The coexistence of iron oxides and sulfides indicates that either the supply of sulfide is limiting or that some iron oxide particles are unreactive.
A method for the enzymic determination of glycogen in chemically preserved material
Authors: Hawkins L. E. , Hutchinson S. , Batten S. D. , Paterson G. L. J. , Lambshead P. J. D. , Rice A. L.
Published: April 2010

We developed a method of measuring glycogen in material preserved in formaldehyde solution or ethanol; it is based on amylase digestion. Comparison of contemporaneous preserved and fresh‐frozen material showed no significant differences. The effects of long‐term storage on glycogen content also appeared small in comparing deep‐sea specimens from the same site and different years.
Seepage meter errors
Authors: Belanger T. V. , Montgomery M. T.
Published: April 2010

Although the seepage meter has been widely used in limnology, measurement errors are commonly ignored. These errors result in the need for meter correction factors due to flow field deflection and frictional resistance and head losses within the meter and prefilled bags to avoid short‐term influx of water caused by the pulling action of deformed bags. Tank‐test data indicate a ratio of measured to actual inseepage of 0.77 (at inseepage rates <20 mm h−1), with a ratio of meter to interstitial seepage flux of 0.50. Provided these precautions are observed and the adjustment factor is applied, field test “point estimates” of seepage inflow with replicate seepage meters generally have relative root‐mean‐square error(s) <20%. Data from measurements at single locations in tank tests indicate a constant bias and show that, once installed, the actual instrument error is even less (∼5%). These errors are small compared to spatial and temporal components of sampling error typically encountered in the field.
In situ sampler‐incubator for simultaneous biological rate measurements via tracers and net chemical change
Authors: Langdon Christopher , Sambrotto Raymond N. , Bitte Ivars
Published: April 2010

A simple device has been developed to facilitate in situ incubations. The hydraulic in situ time‐series sampler (HINTS) facilitates collection and incubation of a large volume of water (16 liters) without need of manipulating the sample at the surface. Injection of isotopic tracers and subsampling can be accomplished remotely via tubing connected to the incubation chamber. HINTS consists of a rigid, clear polycarbonate vessel with a gas‐impermeable plastic incubation bag inside. A two‐way valve permits the incubation chamber to be filled with ambient water or to communicate with the surface via a sampling and tracer‐injection line. Opening and closing the two‐way valve and filling and emptying the incubation chamber are done hydraulically. The HINTS is particularly useful for comparing isotopic and chemical‐change methods of measuring productivity, obtaining time series of chemical properties, physiological rates or organism abundance, and determining net community PQ and C : N assimilation ratios. Preliminary tests suggest good agreement between O2‐ and ∑CO2‐based measurements of net community production. The community photosynthetic quotient averaged 1.4±0.3 (95% C.I.) in four late‐fall and winter measurements.
A QUALITATIVE STUDY OF TECHNOLOGY-BASED TRAINING IN ORGANIZATIONS THAT HIRE AGRICULTURE AND LIFE SCIENCES STUDENTS
Authors: Bedgood Leslie , Murphrey Theresa Pesl , Dooley Kim E.
Published: April 2010

Technological advances have created unlimited opportunities in education. Training and technology have merged to create new methods referred to as technology-based training. The purpose of this study was to identify organizations that hire agriculture and life sciences students for positions involving technology-based training and identify competencies required for these positions from the perspective of the identified organizations. This study describes the technologies that the identified organizations were using to design and deliver technology-based training, the audience to whom the organizations were providing training, and the competencies that the identified organizations were seeking in potential employees. Findings from this study revealed a need for individuals with specialized skills related to technology-based training. Findings specifically suggest seven key competencies needed to work in technology-based training: (a) instructional design, (b) technology/computer skills, (c) the ability to conduct a needs assessment, (d) interpersonal skills, (e) writing skills, (f) planning and organizational skills, and (g) evaluation skills. Study findings lead one to conclude that students with expertise in these competency areas are more marketable in organizations that hire agriculture and life sciences students.
PREDICTING SCORES OF BEGINNING AGRICULTURAL EDUCATION TEACHERS ON THE PRAXIS II EXAMINATION
Authors: Thobega Moreetsi , Miller Greg
Published: April 2010

This descriptive-correlational study predicted performance of beginning agricultural education teachers on principles of learning and teaching (PLT) and Agriculture content (AgC) tests of the PRAXIS II examination using demographic and academic variables. Performance on the PRAXIS II was used for issuing initial teaching licenses to the agricultural education teachers. The study used existing records from the Department Agricultural Education at Iowa State University. Professional education GPA explained significant variability in PLT scores. Males scored higher than females on the AgC test. Agriculture GPA did not explain significant variability in AgC scores. Additional research should be conducted to determine whether similar results would be obtained with other licensure areas. Further research should explore the relationship between gender and performance on the AgC test of the PRAXIS II examination.
RESEARCH PRODUCTIVITY IN THE JOURNAL OF AGRICULTURAL EDUCATION FROM 1996 TO 2005
Authors: Harder Amy , Goff Sam , Roberts T. Grady
Published: April 2010

The purpose of this study was to examine research productivity in the Journal of Agricultural Education from 1996 to 2005 and explain factors that contributed to that productivity. In Volumes 37 to 46, 333 articles were published. The most productive institutions were determined by frequency of the institutional affiliation of article authors. The most productive authors were determined in a similar manner and were also ranked according to appearances as “any author” or “lead author.” A qualitative approach was then taken to develop a better understanding of the factors that contributed to that productivity. The most productive institutions were doctoral-granting institutions. Iowa State University was the leading institution and Texas A&M University closely followed. All of the productive institutions were located in the North-Central and Southern Regions of the American Association for Agricultural Education. The most productive author published 31 articles, and the most productive lead author published 15 articles as lead author. Quality research experience while a doctoral student was identified as an important factor to productivity. Participants identified intrinsic motivation as more important than external recognition and reported that departmental culture had little influence on productivity.
PEER MODELING AND TEACHING EFFICACY: THE INFLUENCE OF TWO STUDENT TEACHERS AT THE SAME TIME
Authors: Roberts T. Grady , Harlin Julie F. , Briers Gary E.
Published: April 2010

The purpose of this study was to determine if placing two teachers at the same school had an influence on teaching efficacy. Bandura’s Model of Triadic Reciprocality and self-efficacy theory guided the inquiry. The population of interest was all student teachers at Texas A&M University. This study was conducted using data collected from a sample of student teachers during a twoyear (four-semester) period from 2004 to 2006. The typical student teacher was a white female pursuing certification as part of an undergraduate degree. Student teachers began the field experience efficacious about their teaching ability, then were less efficacious during the middle of the experience, and finally rebounded to higher levels of efficacy at the end of the experience. It was concluded that there is no difference in teaching efficacy between student teachers placed alone and those placed in pairs. Therefore, this sample was not consistent with Bandura’s theory of the positive influence of peer models.
PRESERVICE AGRICULTURE TEACHERS’ PERCEPTIONS OF CAREER BARRIERS AND SUPPORT
Authors: Rocca Steven J. , Washburn Shannon G.
Published: April 2010

This descriptive study examined the perceptions of career barriers and career support of preservice agriculture teachers and determined if gender differences existed. Data were collected from 215 preservice agriculture teachers using a survey instrument administered by teacher educators at 35 institutions across the nation. Results showed participants were primarily Caucasian, grew up in rural areas, and were considering agricultural education as a first career. Participants perceived the likelihood of career barriers to be low and their level of career support to be high. The issues most likely to become barriers were found to pertain to family responsibilities and relationships, desire to live in a certain area, and an unwillingness to move away. Participants perceived the most support from their teacher educators, agriculture teachers, and cooperating/mentor teachers. No statistical or practical differences were found between perceptions of career barriers and career support for female and male participants.
WORKLOAD DISTRIBUTION AMONG AGRICULTURE TEACHERS
Authors: Torres Robert M. , Ulmer Jonathan D. , Aschenbrener Mollie S
Published: April 2010

Teachers distribute their time in many ways. The study sought to determine how agriculture teachers distribute their time among 11 selected teacher activities (i.e., preparation for instruction; classroom/laboratory teaching; laboratory preparation and/or maintenance; grading/scoring students’ work; administrative duties-program management; professional activities; Supervised Agricultural Experience observations and recording; local FFA activities; non-local FFA activities; Career Development Events preparation; and adult education) over a 15-week period. Additionally, comparisons were made for three teacher types (i.e., studentteachers, first-year teachers, and experience teachers). An additional time category (observation) was observed for student teachers. It was concluded that of the 11 selected areas, all teachers spend the majority of their time planning and providing classroom and laboratory instruction. The least amount of time was spent on adult education. Further, it was concluded that first-year teacher and student teachers display similar use of time in the 11 selected areas over the 15-week period. Recommendations cited include the need for personal development efforts in time-management and a need to better reflect on priorities for distributing time.
INTERNET AS AN INFORMATION SOURCE: ATTITUDES AND USAGE OF STUDENTS ENROLLED IN A COLLEGE OF AGRICULTURE COURSE
Authors: Rhoades Emily B. , Irani Tracy , Telg Ricky , Myers Brian E.
Published: April 2010

With Internet usage in the United States at an all-time high, information technology use in education has continued to increase. Research has shown that many students are utilizing these materials to search out information and assist with completing class assignments. Many college students have described the Internet as a functional tool that helps them to communicate with professors, conduct research, and access library materials. As more and more students and educators use the Internet as a source for information in the classroom, it is important to monitor students’ attitudes and usage to ensure students know how to use technology effectively by recognizing credible sources and utilizing the correct technology for each situation. This study utilizes a descriptive survey to explore the current usage and attitudes toward the Internet by students enrolled in college of agriculture courses at the University of Florida. Findings indicate that these students are substantial users of the Internet and programs like Facebook, MySpace, and search engines. Students indicate believing that the Internet is easy to understand, important, beneficial, believable, and accurate. Recommendations are offered as to what these findings mean for instructors in the classroom.
ASSESSING TEACHER SELF-EFFICACY AND JOB SATISFACTION OF EARLY CAREER AGRICULTURE TEACHERS IN KENTUCKY
Authors: Blackburn J. Joey , Robinson J. Shane
Published: April 2010

The United States is currently facing a shortage of qualified teachers; specifically, agricultural education has recorded shortages for several years. A high percentage of agriculture teachers will leave the profession well before retirement. Those teachers who leave the profession are often dissatisfied with their chosen career and exhibit low levels of teacher self-efficacy and job satisfaction. The purpose of this census study was to describe the current level of teacher self-efficacy and job satisfaction among all early career agriculture teachers (within the first 6 years in the profession) in Kentucky (N = 80) and to determine if a relationship existed between teacher self-efficacy and job satisfaction among these teachers. Teacher self-efficacy was measured through three constructs: student engagement, instructional practices, and classroom management. Early career agriculture teachers in Kentucky are efficacious and satisfied with teaching. A variety of relationships exist between each construct and overall job satisfaction between each group of teachers.
PERCEPTIONS OF SUPERVISION PRACTICES BY AGRICULTURAL EDUCATION STUDENT TEACHERS
Authors: Thobega Moreetsi , Miller Greg
Published: April 2010

The purpose of this study was to describe student teachers’ perceptions and preferences of the type of supervision they experienced while interacting with their university supervisors and cooperating teachers. Results revealed that student teachers perceived both their cooperating teachers and university supervisors to engage in contextual and clinical supervision practices. Cooperating teachers were perceived to use the nondirective style of developmental supervision, whereas most university supervisors were perceived to use the collaborative style. Most student teachers felt that supervision practices from all supervision models were important, with contextual and clinical supervision being most important. Of the developmental supervision styles, most student teachers preferred the collaborative supervision style. Future studies should examine how supervisor beliefs, supervisory situations, and student teachers’ personal and professional characteristics influence the supervisors’ supervisory behaviors.
MENTORING FUNCTIONS PRACTICED BY UNDERGRADUATE FACULTY IN AGRICULTURE
Authors: Wolfe Ashley J. , Retallick Michael S. , Martin Robert , Steiner Charles
Published: April 2010

The literature has indicated that faculty and administrators are often uncertain about how to foster effective mentoring relationships with undergraduate students. This study analyzed the mentoring functions of faculty in the College of Agriculture and Life Sciences at Iowa State University regarding the undergraduate mentoring process. Six mentoring functions (informal contact, role modeling, direct assistance, demonstration, assistance with professional development plans, and observation and feedback) were identified in the literature. A previous questionnaire was used to measure the extent to which faculty practiced each mentoring function. Findings indicated faculty were “often” practicing the mentoring functions. Results indicated consistency in the mentoring process practiced by the faculty in the College of Agriculture and Life Sciences. This study has implications related to faculty training and development. Because of the impact mentoring has on the psychosocial and career development of undergraduates, it is imperative that faculty address each of the six functions of mentoring.
Educational Excellence: Connecting the Right Dots
Authors: Knight James
Published: April 2010

AAAE Distinguished Lecture, Reno, NV, May 22, 2008
Youth Leadership Development: Perceptions and Preferences of Urban Students Enrolled in a Comprehensive Agriculture Program
Authors: Anderson II James C. , Kim Eunyoung
Published: April 2010

This descriptive study explores the perceptions of and preferences for leadership development by students enrolled in a comprehensive urban agriculture program. A total of 284 students from theChicagoHigh School for Agricultural Sciences participated in the study. The results of the study showed that the average respondent was involved in a limited number of school organizations and no community organizations and received the opportunity to learn and practice leadership skills most frequently through sports, work, and FFA. Furthermore, respondents indicated that quality leadership activities should be organized, fun, interactive, and provide real-world application. Respondents also reported that they preferred training to occur within their school, through national workshops, or via international experiences. These findings are instrumental in the discussion of students' awareness of the importance of leadership in their everyday lives, how they currently learn and practice leadership skills, and what quality factors should be considered when developing future leadership experiences.
An Assessment of Problems Faced by High School Agricultural Education Teachers
Authors: Boone Jr. , Boone Deborah A.
Published: April 2010

Leaders in the agricultural education profession established a goal to expand the number of programs offering high school agriculture education over the next 10 years. If the agricultural education profession is going to meet this challenge, it will need to increase its supply of qualified teachers. Currently agricultural education faces a shortage of qualified teachers. The situation is made worse by the attrition of teachers from the profession. One way to increase the number of qualified agricultural education teachers is to reduce the number of teachers who leave the profession early through attrition. The purpose of this study was to identify and quantify the problems faced as beginning teachers and the problems teachers currently face in West Virginia. Financial rewards for teaching were perceived as a moderate to strong problem for teachers as they entered the profession and as a moderate to strong problem for current teachers. Teachers viewed time management, paperwork, and balancing school and home activities as a slight to moderate problem for beginning teachers as well as a slight to moderate problem for current teachers. Respondents also felt facilities-equipment, student motivation, and discipline were slight to moderate problems for beginning teachers.
Attitudes, Educational, and Career Choices of Food and Agricultural Sciences Institute Participants
Authors: Faulkner Paula E. , Baggett Connie D. , Bowen Cathy F. , Bowen Blannie E.
Published: April 2010

Ethnic minority students traditionally pursue degrees and careers in the food and agricultural sciences at rates lower than their non-minority counterparts. To help improve upon this situation, the Food and Agricultural Sciences Institute (FASI) was created to expose academically talented high school students to opportunities within the food and agricultural sciences. FASI provided a week of laboratory experiments, classroom discussions, hands-on activities and demonstrations, and tours of departments in a college of agricultural sciences. Building upon prior research that had assessed the immediate and short term benefits of FASI, this study examined long-term contributions to the attitudes, educational, and career choices of the 1994-2001 FASI participants. Participants from these years were studied because they would have now graduated from high school given that they were high school sophomores and juniors when they participated in FASI. Fifty-seven individuals responded to a survey instrument. The major finding was that the respondents had positive attitudes toward the food and agricultural sciences, but few had pursued degrees or careers in the food and agricultural sciences. Personal factors, parents, and family members most influenced their educational and career choices.
When Leadership Counts: Engaging Youth Through the Washington Leadership Conference
Authors: Stedman Nicole L.P. , Rutherford Tracy A. , Rosser Manda H. , Elbert Chanda
Published: April 2010

The National FFA Organization continues to be a leader in the positive development of youth. Programs sponsored by the FFA provide youth with opportunities to develop their capacity for leadership and citizenship. The Washington Leadership Conference (WLC) is a weeklong conference during the summer that culminates the FFA experience. The WLC's objectives range from defining authentic leadership and relationship building to evaluating ethical decisions and serving communities. Over a 3-year period (2003, 2004, and 2005) the WLC showed consistent results in creating a positive change in the leadership development of its attendees. The greatest area of change was in the WLC's ability to impart new knowledge in its participants, demonstrated by ease of recall for specific facts. However, once participants returned home there was a slight decrease in their ability to carry out behaviors related to the leadership competencies taught at WLC. Overall, results were favorable as to the accomplishment of the WLC's programmatic objectives. Continual support from chapter advisors and online resources would ideally increase the behavioral aspects of students becoming more civically engaged in their home communities and carrying out positive leadership behaviors.
An Analysis of the Priority Needs of Cooperative Extension at the County Level
Authors: Harder Amy , Lamm Alexa J. , Strong Robert
Published: April 2010

Cooperative Extension's role as a relevant provider of nonformal education is dependent upon its ability to improve and adjust in response to internal and external pressures. Periodically conducting needs assessments focused on the Extension organization can aid in Extension's efforts to deliver quality educational programs by pinpointing priority areas in need of improvement. A qualitative analysis of the final reports from the University of Florida's IFAS Extension annual county program review process was conducted to identify challenges and threats facing county Extension offices. Common challenges were marketing deficits, loss of human capital, and technology barriers. Common threats were the economy, increased numbers of urban residents, and insufficient facilities. Developing and implementing strategic plans to resolve the needs identified in this study may increase the effectiveness and efficiency of Extension.
Cognitive Potential: How Different are Agriculture Students?
Authors: Rhoades Emily B. , Ricketts John , Friedel Curt
Published: April 2010

Given the interest, research, and effort extended to help faculty in colleges of agriculture provide educational discourse at higher cognitive levels over the last few years, one would expect that students enrolled in colleges of agriculture would exhibit higher levels of critical thinking and need for cognition. This study thus aimed to discover if the cognitive potential of students enrolled in colleges of agriculture did in fact differ from students enrolled in other colleges. Findings suggest that students enrolled in agriculture had significantly lower GPA, critical thinking disposition, and need for cognition compared with students not in agriculture. Further research needs to determine how instructors are integrating critical thinking into the classroom, as well as instructors' level of cognition. Recommendations based on the findings include further work to increase college of agriculture students' cognitive abilities to help them be prepared for today's world.