Investigation of stochastic-threshold incision models across a climatic and morphological gradient

Abstract. Long-term landscape evolution is controlled by tectonic and climatic forcing acting through surfaces processes. Rivers are the main drivers of continental denudation because they set the base level of most hillslopes and the mechanisms of fluvial incision are a key focus in geomorphological research and require accurate representation and models. River incision is often modeled with the Stream Power Model (SPM), based on the along-stream evolution of drainage area and channel elevation gradient, but can also incorporate more complex processes such as threshold effects and statistical discharge dis-tributions, which are fundamental features of river dynamics. Despite their importance in quantitative geomorphology, such model formulations have been confronted with fields data only in a limited number of cases. Here we investigate the behavior of stochastic-threshold incision models across the south-eastern margin of the Massif Central in France which is characterized by significant relief and the regular occurrence of high-discharge events. Our study is based on a new dedicated dataset combining measurements of discharge variability from gauging stations, denudation rates on 34 basins from 10Be cosmogenic radionuclide (CRN) concentration measurements in river sediments, morphometric analysis of river long-profiles analysis and field observations. This new dataset is used for a systematic investigation of various formulations of the SPM and discuss the importance of incision thresholds. Denudation rates across the SE margin of the Massif Central are in the 20–120 mm/ka range and they positively correlate with slope and precipitations. However, the relationship with steepness index is complex and hints at the importance of taking into account the spatial variations in parameters controlling the SPM. Overall, the range of denudation rate across the margin can mainly be explained using a simple version of the SPM accounting for spatially heterogeneous runoff. More complex formulations including stochastic discharge and incision thresholds yield poorer performances unless spatial variations in bedload characteristics, controlling incision threshold, are taken into account. Our results highlight the importance of the hypotheses used on such threshold in SPM application to field studies and notably the impact of actual constraints on bedload size.

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Influence of discharge variability on denudation rates and relief : example from the south-eastern margin of the Massif Central, France

10.5194/egusphere-egu21-9984 ◽

2021 ◽

Author(s):

Clement Desormeaux ◽

Vincent Godard ◽

Dimitri Lague ◽

Lucilla Benedetti ◽

Jules Fleury ◽

...

Keyword(s):

Extreme Events ◽

River Sediments ◽

Central Area ◽

Complex Model ◽

The South ◽

Massif Central ◽

Eastern Margin ◽

South Eastern ◽

Denudation Rates ◽

River Incision

The evolution of continental relief results from the combined action of tectonic and climatic forcings. These processes do not act continuously but often through punctual events (earthquakes, major floods, landslides) whose integrated action over time (100 Kyr to Myr) leads to the formation of landscapes. The distribution of these extreme events is often described by statistical functions involving power-law relationships between frequency and magnitude, which, coupled with the non-linearity of the geomorphological response and threshold effects for the activation of erosion agents, leads to a complex and often poorly understood relief dynamics.Studying the influence of discharge variability helps to better constrain river incision and long-term relief evolution. The south-eastern margin of the Massif Central (France) is a very interesting target for such investigations because it presents episodes of very intense precipitation focused on the relief resulting in marked differences in the statistical discharges distributions across the landscape. Some theoretical river incision models incorporate such variability (Lague et al., 2005) but they have been confronted with real data only in a limited number of cases (DiBiase et al., 2011; Scherler et al., 2017; Campfort et al., 2020). Here we test these models&#160; in the Massif Central area and in particular on C&#233;vennes, Ard&#232;che and Margeride mountains by quantifying denudation rates using cosmogenic nuclides (10Be), characterizing discharges variability and performing morphological analysis on longitudinal rivers profiles.The analysis of 326 river gauging stations allow us to observe a strong gradient in discharge variability from the external SE border to the interior of the Massif Central. The&#160;10Be concentrations measured from river sediments in 36 catchments imply a large variation of denudation rates between 29 mm/kyr and 126 mm/kyr.&#160;We compare these denudation rates with the spatial distribution of mean annual precipitations, local relief, slope and concavity index, and also integrate all the observations in the frame of a stochastic threshold incision model.&#160;Our results confirm the complex model predictions of non-linear relationships between mean denudation rates and the channel steepness index and their dependence on hydrological variability and run-off.key-words : extreme events, stochastic threshold incision model, denudation rates, discharge variability, morphometric parameters, Massif Central

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Reproduction and biomarker responses of Eisenia fetida after exposure to imidacloprid in biochar-amended soil

Biochar ◽

10.1007/s42773-021-00103-4 ◽

2021 ◽

Author(s):

Ngitheni Winnie-Kate Nyoka ◽

Ozekeke Ogbeide ◽

Patricks Voua Otomo

Keyword(s):

Eisenia Fetida ◽

Field Studies ◽

Application Rate ◽

Land Application ◽

Acetylcholinesterase Inhibition ◽

Beneficial Effects ◽

Pesticide Pollution ◽

The One ◽

The Impact ◽

Amended Soil

AbstractTerrestrial and aquatic ecosystems are increasingly threatened by pesticide pollution resulting from extensive use of pesticides, and due to the lack of regulatory measures in the developing world, there is a need for affordable means to lessen environmental effects. This study aimed to investigate the impact of biochar amendment on the toxicity of imidacloprid to life-cycle parameters and biomarker responses of the earthworm Eisenia fetida. E. fetida was exposed to 10% biochar-amended and non-amended OECD artificial soils spiked with 0, 0.75, 1.5, 2.25 and 3 mg imidacloprid/kg for 28 days. An LC50 of 2.7 mg/kg was only computed in the non-amended soil but not in the biochar-amended soil due to insignificant mortality. The EC50 calculated in the non-amended soil (0.92 mg/kg) for reproduction (fertility) was lower than the one computed in the biochar amended (0.98 mg/kg), indicating a decrease in toxicity in the biochar-amended substrate. Significant weight loss was observed at the two highest imidacloprid treatments in the non-amended soil and only at the highest treatment in the biochar-amended substrate, further highlighting the beneficial effects of biochar. Catalase activity decreased significantly at the two highest concentrations of non-amended soil. Yet, in the amended soil, the activity remained high, especially in the highest concentration, where it was significantly higher than the controls. This indicated more severe oxidative stress in the absence of biochar. In all non-amended treatments, there was a significant acetylcholinesterase inhibition, while lower inhibition percentages were observed in the biochar-amended soil. In most endpoints, the addition of biochar alleviated the toxic effects of imidacloprid, which shows that biochar has the potential to be useful in soil remediation. However, there is still a need for field studies to identify the most effective application rate of biochar for land application.

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Collectivistic Leadership in Context: An Examination of How and When Collective Charismatic Leadership Relates to Unit Functioning

Journal of Leadership & Organizational Studies ◽

10.1177/1548051820986536 ◽

2021 ◽

pp. 154805182098653

Author(s):

Jonathan C. Ziegert ◽

David M. Mayer ◽

Ronald F. Piccolo ◽

Katrina A. Graham

Keyword(s):

Social Inclusion ◽

Task Complexity ◽

Contextual Factors ◽

Negative Relationship ◽

Field Studies ◽

Charismatic Leadership ◽

Interactive Effects ◽

Collective Leadership ◽

Contingency Perspective ◽

The Impact

This research explores the nature of collective leadership by examining the boundary conditions of how and when it relates to unit functioning. Building from a contingency perspective that considers the impact of contextual factors, we propose that collective charismatic leadership will be associated with lowered unit conflict, and this relationship will be strengthened by the contingency elements of individual charismatic leadership, task complexity, and social inclusion. Furthermore, we propose that the interactions of collective charismatic leadership with these contextual factors will relate to performance and satisfaction through conflict. We examine our hypotheses across two unit-level field studies, and the results illustrated that high levels of these contextual factors enhanced the negative relationship between collective charismatic leadership and conflict, which generally mediated the relationships between these interactive effects and performance and satisfaction. The results also highlight the detrimental aspects of collective leadership and how it can relate to reduced unit functioning when it is not aligned with an appropriate context. Overall, these findings begin to provide a more complete picture of collective leadership from a contingency perspective through a greater understanding of when and how it is related to unit functioning.

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Self-Secondaries Formed by Cold Spot Craters on the Moon

Remote Sensing ◽

10.3390/rs13061087 ◽

2021 ◽

Vol 13 (6) ◽

pp. 1087

Author(s):

Yiren Chang ◽

Zhiyong Xiao ◽

Yang Liu ◽

Jun Cui

Keyword(s):

Systematic Investigation ◽

Impact Craters ◽

Spatial Density ◽

Cold Spot ◽

The Moon ◽

Potential Threat ◽

Frequency Distributions ◽

Crater Size ◽

The Impact ◽

Density Pattern

Self-secondaries are a population of background secondaries, and they have been observed on top of impact melt and ballistically emplaced ejecta deposits on various planetary bodies. Self-secondaries are formed by impacts of sub-vertically launched ejecta, but the launch mechanism is not confirmed. The potential threat of self-secondaries to the theoretical and applicable reliability of crater chronology has been noted, but not constrained. Hitherto discovered self-secondaries were located around complex impact craters, but their potential existence around simple craters has not been discovered. Here we report the first discovery of self-secondaries around lunar cold spot craters, which are an extremely young population of simple craters formed within the past ~1 million years on the Moon. Self-secondaries are widespread on layers of cascading flow-like ejecta deposits around cold spot craters. The spatial density of self-secondaries dwarfs that of potential primary craters. The spatial distribution of self-secondaries is highly heterogeneous across the ejecta deposits. With respect to the impactor trajectory that formed cold spot craters, self-secondaries formed at the downrange of the ejecta deposits have the largest spatial density, while those at the uprange have the smallest density. This density pattern holds for all cold spot craters that were formed by non-vertical impacts, but self-secondaries do not exhibit other systematic density variations at different radial distances or at other azimuths with respect to the impactor trajectory. Among known mechanics of ejecting materials to the exterior of impact craters, impact spallation is the most likely scenario to account for the required large ejection velocities and angles to form self-secondaries. The production population of self-secondaries is estimated based on the highly diverse crater size-frequency distributions across the ejecta deposits of cold spot craters. For a better understanding of the impact history on the Moon, a systematic investigation for the effect of self-secondaries on lunar crater chronology is required.

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The nature of entrepreneurial orientation strength: the impact of shared values on firm performance

Journal of Management & Organization ◽

10.1017/jmo.2021.37 ◽

2021 ◽

pp. 1-21

Author(s):

Laurence G. Weinzimmer ◽

Eric J. Michel ◽

Jennifer Robin

Keyword(s):

Firm Performance ◽

Entrepreneurial Orientation ◽

Convergent Validity ◽

Field Studies ◽

Theory And Practice ◽

Interactive Effects ◽

Revenue Growth ◽

Entrepreneurship Theory ◽

The Impact ◽

Strong Culture

Abstract Drawing on Wales, Monsen, and McKelvie's (2011, Entrepreneurship Theory and Practice, 35(5), 895–923) model of entrepreneurial orientation pervasiveness and the strong culture hypothesis (Denison, 1984, Organization Dynamics, 13, 4–22), this study investigates how entrepreneurial orientation (EO) strength, defined as the level of agreement in the shared perceptions of EO, serves as a boundary condition of the EO–firm performance relationship. Four field studies provide evidence for a valid and reliable 10-item multidimensional measure of entrepreneurial orientation, the EO-10, which in turn, may be used to assess EO strength. We establish content and construct validity of the EO-10 (study 1; n = 447 employees), criterion-related validity with revenue growth and sales growth (study 2; n = 412 employees in 43 profit centers), and convergent validity with Covin and Slevin's (1989, Strategic Management Journal, 10, 75–87) 9-item measure (study 3; n = 291 employees). Finally, in study 4 (n = 853 employees nested in 22 organizations), we demonstrate the interactive effects of EO and EO strength on profit growth and revenue growth. In sum, this study provides conceptual and empirical evidence for the importance of EO strength as a moderator of the EO–firm performance relationship.

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The Impact of Pressure and Hydrocarbons on NOx Abatement over Cu- and Fe-Zeolites at Pre-Turbocharger Position

Catalysts ◽

10.3390/catal11030336 ◽

2021 ◽

Vol 11 (3) ◽

pp. 336

Author(s):

Deniz Zengel ◽

Simon Barth ◽

Maria Casapu ◽

Jan-Dierk Grunwaldt

Keyword(s):

Catalytic Reduction ◽

Elevated Pressure ◽

Systematic Investigation ◽

Diesel Oxidation Catalyst ◽

Zeolite Catalysts ◽

Oxidation Catalyst ◽

Pollutant Concentrations ◽

Oxidation Of Hydrocarbons ◽

Negative Effect ◽

The Impact

Positioning the catalysts in front of the turbocharger has gained interest over recent years due to the earlier onset temperature and positive effect of elevated pressure. However, several challenges must be overcome, like presence of higher pollutant concentrations due to the absence or insufficient diesel oxidation catalyst volume at this location. In this context, our study reports a systematic investigation on the effect of pressure and various hydrocarbons during selective catalytic reduction (SCR) of NOx with NH3 over the zeolite-based catalysts Fe-ZSM-5 and Cu-SSZ-13. Using a high-pressure catalyst test bench, the catalytic activity of both zeolite catalysts was measured in the presence and absence of a variety of hydrocarbons under pressures and temperatures resembling the conditions upstream of the turbocharger. The results obtained showed that the hydrocarbons are incompletely converted over both catalysts, resulting in numerous byproducts. The emission of hydrogen cyanide seems to be particularly problematic. Although the increase in pressure was able to improve the oxidation of hydrocarbons and significantly reduce the formation of HCN, sufficiently low emissions could only be achieved at high temperatures. Regarding the NOx conversion, a boost in activity was obtained by increasing the pressure compared to atmospheric reaction conditions, which compensated the negative effect of hydrocarbons on the SCR activity.

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Evaluating the Impact of Two Generalist Predators on the Leafhopper Erasmoneura vulnerata Population Density

Insects ◽

10.3390/insects12040321 ◽

2021 ◽

Vol 12 (4) ◽

pp. 321

Author(s):

Stefan Cristian Prazaru ◽

Giulia Zanettin ◽

Alberto Pozzebon ◽

Paola Tirello ◽

Francesco Toffoletto ◽

...

Keyword(s):

Field Experiments ◽

Field Studies ◽

Generalist Predators ◽

Predator Species ◽

Potted Plants ◽

Naturally Occurring ◽

Orius Majusculus ◽

Limited Effectiveness ◽

Pest Outbreaks ◽

The Impact

Outbreaks of the Nearctic leafhopper Erasmoneura vulnerata represent a threat to vinegrowers in Southern Europe, in particular in North-eastern Italy. The pest outbreaks are frequent in organic vineyards because insecticides labeled for organic viticulture show limited effectiveness towards leafhoppers. On the other hand, the naturally occurring predators and parasitoids of E. vulnerata in vineyards are often not able to keep leafhopper densities at acceptable levels for vine-growers. In this study, we evaluated the potential of two generalist, commercially available predators, Chrysoperla carnea and Orius majusculus, in suppressing E. vulnerata. Laboratory and semi-field experiments were carried out to evaluate both species’ predation capacity on E. vulnerata nymphs. The experiments were conducted on grapevine leaves inside Petri dishes (laboratory) and on potted and caged grapevines (semi-field); in both experiments, the leaves or potted plants were infested with E. vulnerata nymphs prior to predator releases. Both predator species exhibited a remarkable voracity and significantly reduced leafhopper densities in laboratory and semi-field experiments. Therefore, field studies were carried out over two growing seasons in two vineyards. We released 4 O. majusculus adults and 30 C. carnea larvae per m2 of canopy. Predator releases in vineyards reduced leafhopper densities by about 30% compared to the control plots. Results obtained in this study showed that the two predators have a potential to suppress the pest density, but more research is required to define appropriate predator–prey release ratios and release timing. Studies on intraguild interactions and competition with naturally occurring predators are also suggested.

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Enhancing Patient Motivation through Intelligibility in Cardiac Tele-rehabilitation

Interacting with Computers ◽

10.1093/iwc/iwz008 ◽

2019 ◽

Vol 31 (2) ◽

pp. 122-137

Author(s):

Supraja Sankaran ◽

Kris Luyten ◽

Dominique Hansen ◽

Paul Dendale ◽

Karin Coninx

Keyword(s):

Medication Adherence ◽

Exercise Training ◽

Physical Exercise ◽

Health Outcomes ◽

Cardiac Rehabilitation ◽

Field Studies ◽

Activity Levels ◽

Patient Motivation ◽

Physical Exercise Training ◽

The Impact

Abstract Physical exercise training and medication compliance are primary components of cardiac rehabilitation. When rehabilitating independently at home, patients often fail to comply with their prescribed medication and find it challenging to interpret exercise targets or be aware of the expected efforts. Our work aims to assist cardiac patients in understanding their condition better, promoting medication adherence and motivating them to achieve their exercise targets in a tele-rehabilitation setting. We introduce a patient-centric intelligible visualization approach to present prescribed medication and exercise targets to patients. We assessed efficacy of intelligible visualizations on patients’ comprehension in two lab studies. We evaluated the impact on patient motivation and health outcomes in field studies. Patients were able to adhere to medication prescriptions, manage their physical exercises, monitor their progress and gained better self-awareness on how they achieved their rehabilitation targets. Patients confirmed that the intelligible visualizations motivated them to achieve their targets better. We observed an improvement in overall physical activity levels and health outcomes of patients. Research Highlights Presents challenges currently faced in cardiac tele-rehabilitation. Demonstrates how intelligibility was applied to two core aspects of cardiac rehabilitation- promoting medication adherence and physical exercise training. Lab., field and clinical studies to demonstrate efficacy of intelligible visualization, impact on patient motivation and resultant health outcomes. Reflection on how similar HCI approaches could be leveraged for technology-supported management of critical health conditions such as cardiac diseases.

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The impact of leaf shape on the feeding preference of insect herbivores: experimental and field studies with Capsella and Phyllotreta

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.1996.0149 ◽

1996 ◽

Vol 351 (1348) ◽

pp. 1671-1677 ◽

Cited By ~ 28

Keyword(s):

Leaf Shape ◽

Laboratory Data ◽

Leaf Size ◽

Field Studies ◽

Feeding Preference ◽

Insect Herbivores ◽

Flea Beetles ◽

Shape Effects ◽

Leaf Size And Shape ◽

The Impact

Leaves display an enormous array of sizes and shapes. Although these attributes appear to have evolved primarily in response to abiotic conditions in the plant’s habitat, the importance of insect herbivores as additional selective agents is still poorly understood. A necessary requirem ent for leaf size and shape to evolve in response to attack by insects is that insects must respond to and/or be affected by, leaf morphology. We tested leaf-shape preferences in adult flea beetles ( Phyllotreta spp.) feeding on the highly variable rosette leaves of Capsella bursa-pastoris . Contrary to theoretical expectation (Brown & Lawton 1991), leaves with deeply lobed margins were more intensely damaged, both in field-collected and experimental plants. In two ancillary experiments with Capsella , we found that Spodoptera caterpillars showed no preferences for leaf shape, but that adult vine weevils ( Otiorhynchus sulcatus ) did, preferring (as predicted), undivided over divided leaves. We conclude that Brown & Law ton’s (1991) hypothesis is at best weakly supported by laboratory data for vine weevils, refuted by laboratory data for Spodoptera , and consistently refuted by both laboratory and field data for flea beetles. Although the experiment tried to reduce confounding variables to a minimum, interpretation was complicated by correlations between leaf shape and other developmental parameters of the plants, and highlights the difficulty of disentangling leaf-shape effects from other confounding factors.

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Soybean Sensitivity to Florpyrauxifen-benzyl during Reproductive Growth and the Impact on Subsequent Progeny

Weed Technology ◽

10.1017/wet.2017.108 ◽

2017 ◽

Vol 32 (2) ◽

pp. 135-140 ◽

Cited By ~ 3

Author(s):

M. Ryan Miller ◽

Jason K. Norsworthy

Keyword(s):

Plant Height ◽

Field Studies ◽

Yield Reduction ◽

Growth Stages ◽

Soybean Plant ◽

Reproductive Growth ◽

Similar Reduction ◽

Structural Class ◽

Soybean Plants ◽

The Impact

AbstractTo address recent concerns related to auxin herbicide drift onto soybean, a study was developed to understand the susceptibility of the reproductive stage of soybean to a new auxin herbicide compared with dicamba. Florpyrauxifen-benzyl is under development as the second herbicide in a new structural class of synthetic auxins, the arylpicolinates. Field studies were conducted to (1) evaluate and compare reproductive soybean injury and yield following applications of florpyrauxifen-benzyl or dicamba across various concentrations and reproductive growth stages and (2) determine whether low-rate applications of florpyrauxifen-benzyl or dicamba to soybean in reproductive stages would have similar effect on the progeny of the affected plants. Soybean were treated with 0, 1/20, or 1/160, of the 1X rate of florpyrauxifen-benzyl (30 g ai ha−1) or dicamba (560 g ae ha−1) at R1, R2, R3, R4, or R5 growth stage. Soybean plant height and yield was reduced from 1/20X dicamba across all reproductive stages. High drift rates (1/20X) of florpyrauxifen-benzyl also reduced soybean plant height >25% and yield across R1 to R4 stages. Germination, stand, plant height, and yield of the offspring of soybean plants treated with dicamba and florpyrauxifen-benzyl were significantly affected. Dicamba applied at a rate of 1/20X at R4 and R5 resulted in 20% and 35% yield reduction for the offspring, respectively. A similar reduction occurred from florpyrauxifen-benzyl applied at R4 and R5 at the 1/20X rate, resulting in 15% to 24% yield reduction for the offspring, respectively. Based on these findings, it is suggested that growers use caution when applying these herbicides in the vicinity of reproductive soybean.

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