TY - JOUR A1 - Biegert, Thomas A1 - Brady, David A1 - Hipp, Lena T1 - Cross-national variation in the relationship between welfare generosity and single mother employment JF - The annals of the American Academy of Political and Social Science N2 - Reform of the U.S. welfare system in 1996 spurred claims that cuts to welfare programs effectively incentivized single mothers to find employment. It is difficult to assess the veracity of those claims, however, absent evidence of how the relationship between welfare benefits and single mother employment generalizes across countries. This study combines data from the European Union Labour Force Survey and the U.S. Current Population Survey (1992-2015) into one of the largest samples of single mothers ever, testing the relationships between welfare generosity and single mothers’ employment and work hours. We find no consistent evidence of a negative relationship between welfare generosity and single mother employment outcomes. Rather, we find tremendous cross-national heterogeneity, which does not clearly correspond to well-known institutional variations. Our findings demonstrate the limitations of single country studies and the pervasive, salient interactions between institutional contexts and social policies. KW - single mothers KW - employment KW - welfare state benefits KW - cross-national KW - heterogeneity Y1 - 2022 U6 - https://doi.org/10.1177/00027162221120760 SN - 0002-7162 SN - 1552-3349 VL - 702 IS - 1 SP - 37 EP - 54 PB - SAGE Publishing CY - Thousand Oaks ER - TY - JOUR A1 - Hennig, Theresa A1 - Stockmann, Madlen A1 - Kühn, Michael T1 - Simulation of diffusive uranium transport and sorption processes in the Opalinus Clay JF - Applied geochemistry : journal of the International Association of Geochemistry and Cosmochemistry N2 - Diffusive transport and sorption processes of uranium in the Swiss Opalinus Clay were investigated as a function of partial pressure of carbon dioxide pCO(2), varying mineralogy in the facies and associated changes in porewater composition. Simulations were conducted in one-dimensional diffusion models on the 100 m-scale for a time of one million years using a bottom-up approach based on mechanistic surface complexation models as well as cation exchange to quantify sorption. Speciation calculations have shown, uranium is mainly present as U(VI) and must therefore be considered as mobile for in-situ conditions. Uranium migrated up to 26 m in both, the sandy and the carbonate-rich facies, whereas in the shaly facies 16 m was the maximum. The main species was the anionic complex CaUO2(CO3)(3)(2-) . Hence, anion exclusion was taken into account and further reduced the migration distances by 30 %. The concentrations of calcium and carbonates reflected by the set pCO(2) determine speciation and activity of uranium and consequently the sorption behaviour. Our simulation results allow for the first time to prioritize on the far-field scale the governing parameters for diffusion and sorption of uranium and hence outline the sensitivity of the system. Sorption processes are controlled in descending priority by the carbonate and calcium concentrations, pH, pe and the clay mineral content. Therefore, the variation in porewater composition resulting from the heterogeneity of the facies in the Opalinus Clay formation needs to be considered in the assessment of uranium migration in the far field of a potential repository. KW - reactive transport KW - facies KW - heterogeneity KW - carbonate KW - PHREEQC KW - Mont Terri KW - speciation Y1 - 2020 U6 - https://doi.org/10.1016/j.apgeochem.2020.104777 SN - 0883-2927 SN - 1872-9134 VL - 123 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Steding, Svenja A1 - Kempka, Thomas A1 - Kühn, Michael T1 - How insoluble inclusions and intersecting layers affect the leaching process within potash seams JF - Applied Sciences : open access journal N2 - Potash seams are a valuable resource containing several economically interesting, but also highly soluble minerals. In the presence of water, uncontrolled leaching can occur, endangering subsurface mining operations. In the present study, the influence of insoluble inclusions and intersecting layers on leaching zone evolution was examined by means of a reactive transport model. For that purpose, a scenario analysis was carried out, considering different rock distributions within a carnallite-bearing potash seam. The results show that reaction-dominated systems are not affected by heterogeneities at all, whereas transport-dominated systems exhibit a faster advance in homogeneous rock compositions. In return, the ratio of permeated rock in vertical direction is higher in heterogeneous systems. Literature data indicate that most natural potash systems are transport-dominated. Accordingly, insoluble inclusions and intersecting layers can usually be seen as beneficial with regard to reducing hazard potential as long as the mechanical stability of leaching zones is maintained. Thereby, the distribution of insoluble areas is of minor impact unless an inclined, intersecting layer occurs that accelerates leaching zone growth in one direction. Moreover, it is found that the saturation dependency of dissolution rates increases the growth rate in the long term, and therefore must be considered in risk assessments. KW - salt dissolution KW - reactive transport KW - heterogeneity KW - density-driven KW - convection KW - PHREEQC KW - porous media Y1 - 2021 U6 - https://doi.org/10.3390/app11199314 SN - 2076-3417 VL - 11 IS - 19 PB - MDPI CY - Basel ER - TY - JOUR A1 - Hennig, Theresa A1 - Kühn, Michael T1 - Surrogate model for multi-component diffusion of Uranium through Opalinus Clay on the host rock scale JF - Applied Sciences : open access journal N2 - Multi-component (MC) diffusion simulations enable a process based and more precise approach to calculate transport and sorption compared to the commonly used single-component (SC) models following Fick's law. The MC approach takes into account the interaction of chemical species in the porewater with the diffuse double layer (DDL) adhering clay mineral surfaces. We studied the shaly, sandy and carbonate-rich facies of the Opalinus Clay. High clay contents dominate diffusion and sorption of uranium. The MC simulations show shorter diffusion lengths than the SC models due to anion exclusion from the DDL. This hampers diffusion of the predominant species CaUO2(CO3)32-. On the one side, species concentrations and ionic strengths of the porewater and on the other side surface charge of the clay minerals control the composition and behaviour of the DDL. For some instances, it amplifies the diffusion of uranium. We developed a workflow to transfer computationally intensive MC simulations to SC models via calibrated effective diffusion and distribution coefficients. Simulations for one million years depict maximum uranium diffusion lengths between 10 m and 35 m. With respect to the minimum requirement of a thickness of 100 m, the Opalinus Clay seems to be a suitable host rock for nuclear waste repositories. KW - facies KW - uranium speciation KW - sorption KW - reactive transport KW - heterogeneity KW - PHREEQC KW - Mont Terri KW - repository far-field Y1 - 2021 U6 - https://doi.org/10.3390/app11020786 SN - 2076-3417 VL - 11 IS - 2 PB - MDPI CY - Basel ER - TY - JOUR A1 - Vaidya, Shrijana A1 - Schmidt, Marten A1 - Rakowski, Peter A1 - Bonk, Norbert A1 - Verch, Gernot A1 - Augustin, Jürgen A1 - Sommer, Michael A1 - Hoffmann, Mathias T1 - A novel robotic chamber system allowing to accurately and precisely determining spatio-temporal CO2 flux dynamics of heterogeneous croplands JF - Agricultural and forest meteorology N2 - The precise and accurate assessment of carbon dioxide (CO2) exchange is crucial to identify terrestrial carbon (C) sources and sinks and for evaluating their role within the global C budget. The substantial uncertainty in disentangling the management and soil impact on measured CO2 fluxes are largely ignored especially in cropland. The reasons for this lies in the limitation of the widely used eddy covariance as well as manual and automatic chamber systems, which either account for short-term temporal variability or small-scale spatial heterogeneity, but barely both. To address this issue, we developed a novel robotic chamber system allowing for dozens of spatial measurement repetitions, thus enabling CO2 exchange measurements in a sufficient temporal and high small-scale spatial resolution. The system was tested from 08th July to 09th September 2019 at a heterogeneous field (100 m x 16 m), located within the hummocky ground moraine landscape of northeastern Germany (CarboZALF-D). The field is foreseen for a longer-term block trial manipulation experiment extending over three erosion induced soil types and was covered with spring barley. Measured fluxes of nighttime ecosystem respiration (R-eco) and daytime net ecosystem exchange (NEE) showed distinct temporal patterns influenced by crop phenology, weather conditions and management practices. Similarly, we found clear small-scale spatial differences in cumulated (gap-filled) R-eco, gross primary productivity (GPP) and NEE fluxes affected by the three distinct soil types. Additionally, spatial patterns induced by former management practices and characterized by differences in soil pH and nutrition status (P and K) were also revealed between plots within each of the three soil types, which allowed compensating for prior to the foreseen block trial manipulation experiment. The results underline the great potential of the novel robotic chamber system, which not only detects short-term temporal CO2 flux dynamics but also reflects the impact of small-scale spatial heterogeneity. KW - Automatic chamber KW - Net ecosystem exchange (NEE) KW - Gross primary KW - productivity (GPP) KW - Ecosystem respiration (R-eco) KW - Soil erosion KW - Soil KW - heterogeneity Y1 - 2021 U6 - https://doi.org/10.1016/j.agrformet.2020.108206 SN - 0168-1923 SN - 1873-2240 VL - 296 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Schall, Peter A1 - Gossner, Martin M. A1 - Heinrichs, Steffi A1 - Fischer, Markus A1 - Boch, Steffen A1 - Prati, Daniel A1 - Jung, Kirsten A1 - Baumgartner, Vanessa A1 - Blaser, Stefan A1 - Böhm, Stefan A1 - Buscot, Francois A1 - Daniel, Rolf A1 - Goldmann, Kezia A1 - Kaiser, Kristin A1 - Kahl, Tiemo A1 - Lange, Markus A1 - Müller, Jörg Hans A1 - Overmann, Jörg A1 - Renner, Swen C. A1 - Schulze, Ernst-Detlef A1 - Sikorski, Johannes A1 - Tschapka, Marco A1 - Türke, Manfred A1 - Weisser, Wolfgang W. A1 - Wemheuer, Bernd A1 - Wubet, Tesfaye A1 - Ammer, Christian T1 - The impact of even-aged and uneven-aged forest management on regional biodiversity of multiple taxa in European beech forests JF - Journal of applied ecology : an official journal of the British Ecological Society N2 - 1. For managed temperate forests, conservationists and policymakers favour fine-grained uneven-aged (UEA) management over more traditional coarse-grained even-aged (EA) management, based on the assumption that within-stand habitat heterogeneity enhances biodiversity. There is, however, little empirical evidence to support this assumption. We investigated for the first time how differently grained forest management systems affect the biodiversity of multiple above- and below-ground taxa across spatial scales. 2. We sampled 15 taxa of animals, plants, fungi and bacteria within the largest contiguous beech forest landscape of Germany and classified them into functional groups. Selected forest stands have been managed for more than a century at different spatial grains. The EA (coarse-grained management) and UEA (fine-grained) forests are comparable in spatial arrangement, climate and soil conditions. These were compared to forests of a nearby national park that have been unmanaged for at least 20years. We used diversity accumulation curves to compare -diversity for Hill numbers D-0 (species richness), D-1 (Shannon diversity) and D-2 (Simpson diversity) between the management systems. Beta diversity was quantified as multiple-site dissimilarity. 3. Gamma diversity was higher in EA than in UEA forests for at least one of the three Hill numbers for six taxa (up to 77%), while eight showed no difference. Only bacteria showed the opposite pattern. Higher -diversity in EA forests was also found for forest specialists and saproxylic beetles. 4. Between-stand -diversity was higher in EA than in UEA forests for one-third (all species) and half (forest specialists) of all taxa, driven by environmental heterogeneity between age-classes, while -diversity showed no directional response across taxa or for forest specialists. 5. Synthesis and applications. Comparing EA and uneven-aged forest management in Central European beech forests, our results show that a mosaic of different age-classes is more important for regional biodiversity than high within-stand heterogeneity. We suggest reconsidering the current trend of replacing even-aged management in temperate forests. Instead, the variability of stages and stand structures should be increased to promote landscape-scale biodiversity. KW - beta diversity KW - forest specialists KW - gamma diversity KW - heterogeneity KW - Hill numbers KW - saproxylic beetles KW - spatial grain KW - species accumulation curve KW - species richness KW - species turnover Y1 - 2017 U6 - https://doi.org/10.1111/1365-2664.12950 SN - 0021-8901 SN - 1365-2664 VL - 55 IS - 1 SP - 267 EP - 278 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Ringel, Lisa Maria A1 - Somogyvári, Márk A1 - Jalali, Mohammadreza A1 - Bayer, Peter T1 - Comparison of hydraulic and tracer tomography for discrete fracture network inversion JF - Geosciences N2 - Fractures serve as highly conductive preferential flow paths for fluids in rocks, which are difficult to exactly reconstruct in numerical models. Especially, in low-conductive rocks, fractures are often the only pathways for advection of solutes and heat. The presented study compares the results from hydraulic and tracer tomography applied to invert a theoretical discrete fracture network (DFN) that is based on data from synthetic cross-well testing. For hydraulic tomography, pressure pulses in various injection intervals are induced and the pressure responses in the monitoring intervals of a nearby observation well are recorded. For tracer tomography, a conservative tracer is injected in different well levels and the depth-dependent breakthrough of the tracer is monitored. A recently introduced transdimensional Bayesian inversion procedure is applied for both tomographical methods, which adjusts the fracture positions, orientations, and numbers based on given geometrical fracture statistics. The used Metropolis-Hastings-Green algorithm is refined by the simultaneous estimation of the measurement error’s variance, that is, the measurement noise. Based on the presented application to invert the two-dimensional cross-section between source and the receiver well, the hydraulic tomography reveals itself to be more suitable for reconstructing the original DFN. This is based on a probabilistic representation of the inverted results by means of fracture probabilities. KW - hydraulic tomography KW - tracer tomography KW - DFN KW - Bayesian inversion KW - heterogeneity KW - fracture KW - hydrogeophysics Y1 - 2019 U6 - https://doi.org/10.3390/geosciences9060274 SN - 2076-3263 VL - 9 IS - 6 PB - MDPI CY - Basel ER - TY - JOUR A1 - Dietrich, Julia A1 - Lazarides, Rebecca T1 - Gendered development of motivational belief patterns in mathematics across a school year and career plans in math-related fields JF - Frontiers in psychology N2 - Rooted in Eccles and colleagues' expectancy-value theory, this study aimed to examine how expectancies and different facets of task value combine to diverse profiles of motivational beliefs, how such complex profiles develop across a school year, and how they relate to gender and career plans. Despite abundant research on the association between gender and motivational beliefs, there is a paucity of knowledge regarding the gendered development of student motivational belief profiles in specific domains. Using latent-transition analysis in a sample of N = 751 ninth to tenth graders (55.9% girls), we investigated girls' and boys' development of motivational belief profiles (profile paths) in mathematics across a school year. We further analyzed the association between these profile paths and math-related career plans. The results revealed four motivational belief profiles: high motivation (intrinsic and attainment oriented), balanced above average motivation, average motivation (attainment and cost oriented), and low motivation (cost oriented). Girls were less likely than expected by chance to remain in the high motivation profile, while the opposite was true for boys. The math-relatedness of students' career plans was significantly higher in the "stable high motivation" profile path than in all other stable profile paths. KW - motivation in mathematics KW - latent transition analysis/latent profile analysis KW - expectancy-value theory KW - heterogeneity KW - adolescence Y1 - 2019 U6 - https://doi.org/10.3389/fpsyg.2019.01472 SN - 1664-1078 VL - 10 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Koussoroplis, Apostolos-Manuel A1 - Wacker, Alexander T1 - Covariance modulates the effect of joint temperature and food variance on ectotherm life-history traits JF - Ecology letters N2 - Understanding animal performance in heterogeneous or variable environments is a central question in ecology. We combine modelling and experiments to test how temperature and food availability variance jointly affect life-history traits of ectotherms. The model predicts that as mean temperatures move away from the ectotherm's thermal optimum, the effect size of joint thermal and food variance should become increasingly sensitive to their covariance. Below the thermal optimum, performance should be positively correlated with food–temperature covariance and the opposite is predicted above it. At lower temperatures, covariance should determine whether food and temperature variance increases or decreases performance compared to constant conditions. Somewhat stronger than predicted, the covariance effect below the thermal optimum was confirmed experimentally on an aquatic ectotherm (Daphnia magna) exposed to diurnal food and temperature variance with different amounts of covariance. Our findings have important implications for understanding ectotherm responses to climate-driven alterations of thermal mean and variance. KW - Biotic interactions KW - co-limitation KW - Daphnia KW - environmental fluctuations KW - heterogeneity KW - variability KW - vertical migration KW - zooplankton Y1 - 2016 U6 - https://doi.org/10.1111/ele.12546 SN - 1461-023X SN - 1461-0248 VL - 19 SP - 143 EP - 152 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Jeltsch, Florian A1 - Grimm, Volker A1 - Reeg, Jette A1 - Schlägel, Ulrike E. T1 - Give chance a chance BT - from coexistence to coviability in biodiversity theory JF - Ecosphere N2 - A large part of biodiversity theory is driven by the basic question of what allows species to coexist in spite of a confined number of niches. A substantial theoretical background to this question is provided by modern coexistence theory (MCT), which rests on mathematical approaches of invasion analysis to categorize underlying mechanisms into factors that reduce either niche overlap (stabilizing mechanisms) or the average fitness differences of species (equalizing mechanisms). While MCT has inspired biodiversity theory in the search for these underlying mechanisms, we feel that the strong focus on coexistence causes a bias toward the most abundant species and neglects the plethora of species that are less abundant and often show high local turnover. Given the more stochastic nature of their occurrence, we advocate a complementary cross-level approach that links individuals, small populations, and communities and explicitly takes into account (1) a more complete inclusion of environmental and demographic stochasticity affecting small populations, (2) intraspecific trait variation and behavioral plasticity, and (3) local heterogeneities, interactions, and feedbacks. Focusing on mechanisms that drive the temporary coviability of species rather than infinite coexistence, we suggest a new approach that could be dubbed coviability analysis (CVA). From a modeling perspective, CVA builds on the merged approaches of individual-based modeling and population viability analysis but extends them to the community level. From an empirical viewpoint, CVA calls for a stronger integration of spatiotemporal data on variability and noise, changing drivers, and interactions at the level of individuals. The resulting large volumes of data from multiple sources could be strongly supported by novel techniques tailored to the discovery of complex patterns in high-dimensional data. By complementing MCT through a stronger focus on the coviability of less common species, this approach can help make modern biodiversity theory more comprehensive, predictive, and relevant for applications. KW - behavioral plasticity KW - biodiversity KW - coexistence KW - community theory KW - coviability analysis KW - demographic noise KW - environmental noise KW - heterogeneity KW - individual-based modeling KW - intraspecific trait variation KW - modern coexistence theory KW - population viability analysis Y1 - 2019 U6 - https://doi.org/10.1002/ecs2.2700 SN - 2150-8925 VL - 10 IS - 5 PB - ESA CY - Ithaca, NY ER -