Mob Grazing Results in High Forage Utilization and Reduced Western Snowberry Size

Mob-grazing strives to maximize forage utilization and minimize selective grazing by using high stocking densities in small paddocks for short durations (12–24 hr). Rotational-grazing uses low stocking densities for a longer time period, retaining about half of the original available forage; although selective grazing can occur. Three cattle (Bos taurus × Bos indicus) grazing intensities: mob- (stocking densities from 32,000 to 67,000 kg ha−1; duration—24 hr); rotation (stocking density—2500 kg ha−1; duration—35 d); and non-grazed systems were compared based on forage utilization and changes to western snowberry (Symphoricarpos occidentalis) (WS) patch volume in a 2-year South Dakota study. Pre- and post-grazing forage height was measured every 2.5 m along multiple 50-m transects with WS patch volume measured every 5 m. Forage utilization (consumed and trampled) ranged from 42 to 90% in mob-grazed areas, and harvest efficiency (forage consumed) ranged from 15 to 64%. WS patch volumes decreased by ≥45% in mob-grazed treatments compared with no change in rotational-grazing and increased cover in non-grazed areas. WS pre-graze patch size influenced mob-grazing impact; patches >6500 cm3 were browsed or trampled to a greater extent than smaller patches

TRUST IN TECHNOLOGY: DEVELOPMENT OF A SET OF CONSTRUCTS AND MEASURES

Trust plays an important role in many Information Systems (IS)-enabled situations. Most IS research employs trust as a measure of interpersonal or interfirm relations, such as trust in a Web vendor or a virtual team member. Although trust in other people is important, this paper suggests that trust in the information technology (IT) itself may also play a role in shaping IT-related beliefs and behavior. To advance trust and technology research, this paper presents a set of trust in technology construct definitions and measures. These construct measures will be examined using tests of convergent, discriminant, and nomological validity. This study will contribute to the literature by offering a) a framework for distinguishing between trust in people and trust in technology, b) offering a theory based set of definitions necessary forminvestigating different forms of trust, and c) developing measures useful to research and practice for evaluating trust in technology

Mob vs. Rotational Grazing: Impact on Forage Use and Artemisia absinthium

Short duration (≤24 h), high stocking density grazing systems (e.g., mob grazing) mimics historic prairie grazing patterns of American bison (Bison bison), and should minimize selective grazing. We compared mob [125 cow-calf pairs on either 0.65 ha for 12 h; or 1.3 ha for 24 h] vs. rotational [25 cow-calf pairs on 8.1 ha for 20 days starting in mid-May with or without 2,4-D application prior to grazing; and 15 days starting mid-April (no herbicide)] grazing systems based on forage utilization and impact to Artemisia absinthium (absinth wormwood) in a tall grass pasture of Eastern South Dakota. Grass height and density, and Artemisia absinthium patch volume were quantified pre- and post-grazing at sampling points along multiple transects. Mob grazing had >75% forage utilization, whereas rotational grazing averaged 50% (all consumption). Within a grazing season, three grazing systems suppressed Artemisia absinthium patches with rotation/spray (100% decrease) > mob (65 ± 10% decrease) > mid-May rotation (41 ± 16% decrease), whereas Artemisia absinthium patches in the mid-April rotation followed by summer rest dramatically increased in size. Artemisia absinthium patches <19,000 cm3 were browsed, whereas larger patches were trampled in mob-grazed areas, but avoided in rotational grazing. All Artemisia absinthium patches had regrowth the year following any grazing event

Effects of Low-Level Additions of Salt on Decomposition Rates and Plant Sodium Concentrations in a Southeastern, US Riparian System

Connor Gruntz is an undergraduate student in the School of Biological Sciences at Louisiana Tech University. Sally Entrekin is a faculty member in the Biology Department at the University of Central Arkansas. Michelle Evans-White is a Professor in the Department of Biological Sciences at the University of Arkansas. Natalie Clay is an Assistant Professor in the School of Biological Sciences at Louisiana Tech Universit

Effects of Low-Level Salt Additions on Plant Growth and Implications for Riparian Detrital Processing

The abstract for this presentation can be downloaded by clicking on the blue download button

Pesticide concentrations in frog tissue and wetland habitats in a landscape dominated by agriculture

Habitat loss and exposure to pesticides are likely primary factors contributing to amphibian decline in agricultural landscapes. Conservation efforts have attempted to restore wetlands lost through landscape modifications to reduce contaminant loads in surface waters and providing quality habitat to wildlife. The benefits of this increased wetland area, perhaps especially for amphibians, may be negated if habitat quality is insufficient to support persistent populations. We examined the presence of pesticides and nutrients in water and sediment as indicators of habitat quality and assessed the bioaccumulation of pesticides in the tissue of twonative amphibian species Pseudacris maculata (chorus frogs) and Lithobates pipiens (leopard frogs) at six wetlands (3 restored and 3 reference) in Iowa, USA. Restored wetlands are positioned on the landscape to receive subsurface tile drainage water while referencewetlands receive water fromoverland run-off and shallow groundwater sources. Concentrations of the pesticides frequently detected inwater and sediment samples were not different between wetland types. The median concentration of atrazine in surface water was 0.2 μg/L. Reproductive abnormalities in leopard frogs have been observed in other studies at these concentrations. Nutrient concentrations were higher in the restored wetlands but lower than concentrations thought lethal to frogs. Complex mixtures of pesticides including up to 8 fungicides, some previously unreported in tissue, were detected with concentrations ranging from 0.08 to 1500 μg/kg wet weight. No significant differences in pesticide concentrations were observed between species, although concentrations tended to be higher in leopard frogs compared to chorus frogs, possibly because of differences in life histories. Our results provide information on habitat quality in restored wetlands that will assist state and federal agencies, landowners, and resource managers in identifying and implementing conservation and management actions for these and similar wetlands in agriculturally dominated landscapes

Spring Clipping, Fire, and Simulated Increased Atmospheric Nitrogen Deposition Effects on Tallgrass Prairie Vegetation

Defoliation aimed at introduced cool-season grasses, which uses similar resources of native grasses, could substantially reduce their competitiveness and improve the quality of the northern tallgrass prairie. The objective was to evaluate the use of early season clipping and fire in conjunction with simulated increased levels of atmospheric nitrogen deposition on foliar canopy cover of tallgrass prairie vegetation. This study was conducted from 2009 to 2012 at two locations in eastern South Dakota. Small plots arranged in a split-plot treatment design were randomized in four complete blocks on a warm-season grass interseeded and a native prairie site in east-central South Dakota. The whole plot consisted of seven treatments: annual clip, biennial clip, triennial clip, annual fire, biennial fire, triennial fire, and undefoliated control. The clip plots consisted of weekly clipping in May to simulate heavy grazing. Fire was applied in late April or early May. The subplot consisted of nitrogen applied at 0 or 15 kg N · ha−1 in early June. All treatments were initially applied in 2009. Biennial and triennial treatments were reapplied in 2011 and 2012, respectively. Canopy cover of species/major plant functional groups was estimated in late August/early September. Annual clipping was just as effective as annual fire in increasing native warm-season grass and decreasing introduced cool-season grass cover. Annual defoliation resulted in greater native warm-season grass cover, less introduced cool-season grass cover, and less native cool-season grass cover than biennial or triennial defoliation applications. Low levels of nitrogen did not affect native warm-season grass or introduced cool-season cover for any of the defoliation treatments, but it increased introduced cool-season grass cover in the undefoliated control at the native prairie site. This study supports the hypothesis that appropriately applied management results in consistent desired outcomes regardless of increased simulated atmospheric nitrogen depositions

Exploring the amphibian exposome in an agricultural landscape using telemetry and passive sampling

This is the first field study of its kind to combine radio telemetry, passive samplers, and pesticide accumulation in tissues to characterize the amphibian exposome as it relates to pesticides. Understanding how habitat drives exposure in individuals (i.e., their exposome), and how that relates to individual health is critical to managing species in an agricultural landscape where pesticide exposure is likely. We followed 72 northern leopard frogs (Lithobates pipiens) in two agricultural wetlands for insight into where and when individuals are at high risk of pesticide exposure. Novel passive sampling devices (PSDs) were deployed at sites where telemetered frogs were located, then moved to subsequent locations as frogs were radio-tracked. Pesticide concentration in PSDs varied by habitat and was greatest in agricultural fields where frogs were rarely found. Pesticide concentrations in frogs were greatest in spring when frogs were occupying wetlands compared to late summer when frogs occupied terrestrial habitats. Our results indicate that habitat and time of year influence exposure and accumulation of pesticides in amphibians. Our study illustrates the feasibility of quantifying the amphibian exposome to interpret the role of habitat use in pesticide accumulation in frogs to better manage amphibians in agricultural landscapes

Relationships among nutrient enrichment, detritus quality and quantity, and large-bodied shredding insect community structure

Anthropogenic nutrient enrichment of forested headwater streams can enhance detrital quality, decrease standing stocks, and alter the community structure of detrivorous insects, reducing nutrient retention and decreasing ecosystem functioning. Our objective was to determine if stoichiometric principles could be used to predict genus-specific shifts in shredding insect abundance and biomass across a dissolved nutrient and detritus food quality/quantity gradient. Detritus, insect, and water samples were collected from 12 Ozark Highland headwater streams. Significant correlations were found between stream nutrients and detrital quality but not quantity. Abundance and biomass responses of four out of five tested genera were accurately predicted by consumerresource stoichiometric theory. Low carbon:phosphorus (C:P) shredders responded positively to increased total phosphorus and/or food quality, and high C:P shredders exhibited neutral or negative responses to these variables. Genus-specific declines were correlated with decreased overall biomass in shredder assemblages, potentially causing disruptions in nutrient flows to higher level consumers with nutrient enrichment. This work provides further evidence that elevated nutrients may negatively impact shredding insect communities by altering the stoichiometry of detritus–detritivore interactions. A better understanding of stoichiometric mechanisms altering macroinvertebrate populations is needed to help inform water quality criteria for the management of headwater streams

A Rapid Method for Measuring Feces Ammonia-Nitrogen and Carbon Dioxide-Carbon Emissions and Decomposition Rate Constants

A rapid approach is needed for determining the eff ectiveness of precision conservation on soil health as evaluated using CO2 and NH3 emissions. Th is study demonstrated an approach for calculating CO2–C and NH3–N emissions and associated rate constants when feces were applied to bare soil or soil + vegetation. In addition, point CO2–C emission measurements were compared with near continuous measurements. The CO2–C emissions were measured at 2 h intervals over 20 d, whereas ammonia volatilization was measured three times daily for 7 d. Total CO2–C emissions over 20 d were 5% lower [186 g CO2–C (m2 × 20 d) –1] than point measurement collected at 1100 h every day (197 g CO2–C (m2 × 20 d) –1), and about 10% lower than if collected every 2 d [206 g CO2–C (m2 × 20 d) –1]. A Fast Fourier transformation (FFT) showed that temperature and NH3–N and CO2–C emissions followed diurnal cycles and that they were in-phase with each other. Over 7 d, 20% of feces NH4–N was volatilized and that this loss was similar when feces were applied over vegetation or mixed into the soil. Feces additions increased the amplitude of the CO2–C diurnal cycle, and the fecal-C first-order rate degradation constants were higher when mixed with soil [0.0109 ± 0.0043 g(g×d) –1, p = 0.1] than applied over vegetation [0.00454 ± 0.00336 g(g×d) –1, p = 0.1]