No Place Like Home? Graduate Migration in Germany

The aim of this paper is to identify migration patterns of the highly educated, placing special emphasis on imbalances across regions. For this, we use data from a representative and longitudinal graduate survey in Germany with information about the work and migration history during the first 5 years after graduation. With regional funding of higher education, the number of graduates who leave the university region and the resulting net balance matter. It is equally important to understand whether economically weak and strong regions are affected differently and if graduates of study programs which are more or less costly to provide display different migration patterns. The findings show that stronger regions are more attractive for graduates. However, graduates of expensive study fields are less attached to their university region than graduates of inexpensive study fields if the university region has an above‐average GDP per capita. There is no evidence, however, that this also holds for regions with a below‐average GDP per capita. These weaker regions thus face a number effect, but there is no composition effect as far as the fields of study are concerned.     

Trace elements bioavailability to <Emphasis Type="Italic">Triticum aestivum</Emphasis> and <Emphasis Type="Italic">Dendrobaena veneta</Emphasis> in a multielement-contaminated agricultural soil amended with drinking water treatment residues

Purpose

The in situ stabilization of multielement-contaminated agricultural soils has limited effectiveness when using common single amendments. This study examined the use of drinking water treatment residues (WTR), based on (hydr)oxides of Fe, Al, or Mn, as a cost-effective solution to optimize the immobilization of metals (Cd, Pb, Zn) and As.

Materials and methods

Trace elements (TE) bioavailability was assessed under semi-controlled conditions in a pot study cultivating winter wheat (Triticum aestivum L. cv. Tiger) until maturity. An Fe-based WTR and a Mn-based WTR, applied at rates of 0.5 and 1% (m/m), were related to effects of lime marl (LM) application. Additionally, a bioassay with earthworms (Dendrobaena veneta) was conducted. Both bioassays were compared with measurements of NH₄NO₃-soluble, diffusive gradients in thin film (DGT)-available and soil solution TE concentrations, representing well-established surrogates for mimicking the bioavailable element fractions in soil.

Results and discussion

The application of the Fe-based WTR reduced As accumulation in vegetative wheat tissues (by up to 75%) and earthworms (by up to 41%), which corresponded with the findings from soil chemical analyses and improved plant growth and earthworm body weight. However, As concentrations in cereal grains were not affected, Cd or Pb accumulation by wheat was not mitigated, and Zn uptake was enhanced. By contrast, the Mn-based WTR effected the greatest reduction in Pb uptake, and lowered Cd transfer to wheat grain (by up to 25%). Neither the NH₄NO₃-soluble nor DGT-available concentrations matched with Cd and Zn accumulation in plants or earthworms, indicating interferences due to competition for binding sites according to the biotic ligand model.

Conclusions

The results obtained in this study suggest that a bioassay with key species prior to field application should be mandatory when designing in situ stabilization options. The application of WTR to an agricultural soil strongly affected TE bioavailability to plants and earthworms. Low application rates tended to improve biomass production of biota. Higher application rates involved risks (e.g., P fixation, TE inputs), and none of the amendments tested could immobilize all targeted elements.

     

A data-driven fuzzy approach to simulate the critical shear stress of mixed cohesive/non-cohesive sediments

Purpose

The critical shear stress of cohesive and mixed cohesive/non-cohesive sediments is affected by multiple interacting physical, chemical and biological parameters. There are various mathematical approaches in the scientific literature for computing critical shear stress. However, processes that influence sediment stability are still not fully understood, and available formulas differ considerably. These discrepancies in the literature arise from random system behaviour (natural variability of the sediments), different definitions of the critical shear stress, different measurement techniques and different model frameworks (scope of the parameters, undisturbed versus artificial sediment samples). While analytical approaches fail to address the involved uncertainties, fuzzy logic-based models integrate uncertainty and imprecision.

Materials and methods

With this in mind, a data-driven neuro-fuzzy model (ANFIS) was used to determine the critical shear stress based on sediment characteristics such as wet bulk density and grain size distribution. In order to select model predictors systematically, an automated stepwise regression algorithm was applied. The database for this analysis consisted of 447 measurements of the critical shear stress originating from 64 undisturbed sediment samples.

Results and discussion

The study identified clay content as the primarily controlling variable for erosion resistance. Depending on the characteristics of the sampling location, the bulk density was also selected as a model predictor. In comparison to analytical models that are available in the scientific literature, the fuzzy model achieved higher correlation coefficients between measured and predicted data.

Conclusions

The neuro-fuzzy-model includes uncertainties of input variables and their interactions directly. Thus, it provides a reliable method for the prediction of erosion thresholds of cohesive/non-cohesive mixtures. It was also shown that this approach requires fewer measured variables as well as fewer assumptions than the models it was compared to.

     

Competence of <Emphasis Type="Italic">Xanthomonas campestris</Emphasis> from Cruciferous Weeds and Wallflower (<Emphasis Type="Italic">Erysimum cheiri</Emphasis>) to Induce Black Rot in Cabbage

Aphanomyces euteiches Drechsler is an oomycete pathogen of leguminous crops that causes root rot, a severe disease of pea (Pisum sativum L.) worldwide. An improved understanding of the genetic structure of A. euteiches populations would increase knowledge of pathogen evolution and assist in the design of strategies to develop pea cultivars and germplasm with stable disease resistance. Twenty six primers pairs were used to amplify Sequence Related Amplified Polymorphisms (SRAP) among 49 A. euteiches isolates sampled from pea. A total of 190 polymorphic SRAP bands were generated, of which 82 were polymorphic between all the A. euteiches isolates. The percentage of polymorphic bands per primer pair ranged from 22 to 75%. According to the PIC value estimated for each marker, 60% of the SRAP markers were highly to reasonably informative (PIC > 0.25). Genetic structure of A. euteiches populations sampled in different American and French locations showed low to high genetic diversity within populations. The largest variation occurred within countries, with a total estimated genetic diversity of 0.477 and 0.172 for American and French populations, respectively. This was particularly evident from a principal component analysis (PCA) and a Minimum Spanning Networks (MSN) based on genetic profiles of isolates, which generated two different clusters, one corresponding to the French isolates and four American isolates (MV1, MV5, MV7, Ath3), and the other to American isolates. A. euteiches populations from cultivated pea in France appeared as a single unstructured population, whereas American isolates of A. euteiches diverged into three different populations.     

Waste management in recirculating aquaculture system through bacteria dissimilation and plant assimilation

Wastewater management and disposal in aquaculture is becoming increasingly important due to stringent water regulations regarding waste discharges into natural water systems. Recirculation aquaculture is one of the technologies designed to reduce waste discharge through the nitrification process. However, nitrification results in nitrate accumulation which is normally reduced by dilution through water exchange. Water exchange is only possible with sufficient water. Although nitrification is a conventional process, it has limitations because the autotrophic bacteria require long start-up and multiplication periods. The nitrifiers require high levels of oxygen with relatively higher aeration costs. Moreover, the bacteria are sensitive to rapid changes in pH, temperature, and flow rate. Denitrification can be a solution to the limitations of nitrification since denitrifiers are most abundant in the natural environment and have higher growth rates than nitrifiers. In addition, the process reduces energy costs since there is no need for aeration, water consumption is also reduced drastically since water exchange is minimized. Organic loading can be reduced when fish waste is utilized as a carbon source. An alternative process to manage aquaculture wastes is through anaerobic ammonium oxidation (anammox), where ammonia and nitrite are converted into nitrogen gas. Anammox can efficiently reduce ammonia and nitrites from culture water, but it has not received wide application in aquaculture. Aquaculture wastewater contains nutrients which are essential for plant growth. The plants maintain good water quality by absorbing the dissolved nutrients. Denitrification, anammox, and nutrient uptake by plants are feasible strategies to reduce wastes from aquaculture effluents.     

Cold tolerance during juvenile development in sorghum: a comparative analysis by genomewide association and linkage mapping

Improved cold tolerance during the juvenile phase is a major breeding goal to develop new sorghum cultivars suitable as an alternative energy crop in temperate regions. The objectives of this study were to identify marker‐trait associations for cold tolerance in a sorghum diversity panel fingerprinted with 2620 single nucleotide polymorphism (SNP) markers and to detect quantitative trait loci (QTL) in two F_2:3 populations. Traits of interest were dry matter growth rate (DMGR), leaf appearance rate (LAR), chlorophyll content (SPAD) and chlorophyll fluorescence (F_v′/F_m′ and Ф_PSII) in relation to temperature. The association panel comprised 194 genotypes, while the F_2:3 populations consisted of 80 and 92 genotypes. All populations were tested under controlled conditions in a minimum of four temperature regimes ranging from 9.4°C to 20.8°C. QTL were identified for means across environments and regression parameters describing temperature effects. Several marker‐trait associations for mean (m) DMGR, base temperature (T_b) of SPAD and Ф_PSII and temperature effect on LAR were validated by QTL detected in population 1 or 2. Promising QTL regions were found on chromosomes SBI‐01, SBI‐02, SBI‐03, SBI‐04, SBI‐06 and SBI‐09, among them genomic regions where candidate genes involved in the C‐repeat binding pathway or encoding cold‐shock proteins are located.     

Environmental and spatial characterisation of bacterial community composition in soil to inform sampling strategies

Soil physicochemical properties and microbial communities are highly heterogeneous and vary widely over spatial scales, necessitating careful consideration of sampling strategies to provide representative and reproducible soil samples across field sites. To achieve this, the study aimed to establish appropriate sampling methodology and to determine links between the variability of parameters, utilising two sampling strategies. The first (design 1) involved extracting 25 cores from random locations throughout the field and pooling them into five sets of five cores. The second (design 2) involved a further 25 cores within five 1 m² sub-plots. Sub-samples from each sub-plot were pooled in order to determine between and within sub-plot variability. All samples were analysed independently and as pooled sub-samples. Results indicate that pooling spatially separated samples significantly reduced the variability in pH, compared to individual samples. Pooling samples from a small area resulted in lower within sub-plot variability than between sub-plots for pH and bacterial community composition assessed by terminal-restriction fragment length polymorphism analysis. Following multivariate statistical analysis, a large amount of variation in community composition was explained by soil pH, which is remarkable given the relatively small size of the sampling area and minor differences in pH. Moisture content was also important in determining bacterial communities in the random design (design 1). In the 1 m² sub-plot design (design 2), the spatial location of the plots explained a large degree of the variation in bacterial community composition between plots, which was due to spatial autocorrelation of pH and possible additional environmental parameters. This study emphasises the importance of sampling design for obtaining representative samples from soil.     

Efficacy of an intranasal modified live bovine respiratory syncytial virus and temperature-sensitive parainfluenza type 3 virus vaccine in 3-week-old calves experimentally challenged with PI3V

Two experimental parainfluenza type 3 virus (PI3V) challenge studies were undertaken to evaluate the efficacy of a single intranasal dose of an attenuated live vaccine containing modified live bovine respiratory syncytial virus (BRSV) and temperature-sensitive PI3V in 3-week-old calves. In the first study, vaccine efficacy was evaluated in colostrum deprived calves. Nasal shedding of PI3V was highly significantly reduced in vaccinated calves challenged 10 days or 21 days after vaccination. In the second study, vaccine efficacy was assessed in calves with maternal antibodies against PI3V by challenge 66 days post-vaccination. Vaccination also significantly reduced PI3V excretion after challenge in this study. In both studies, clinical signs after challenge were very mild and were not different between vaccinated and control calves.     

Lichen diversity in temperate montane forests is influenced by forest structure more than climate

Although the effect of forest management on lichens in temperate forests has been widely examined, little is known about the influence of management-related factors on their biodiversity relative to factors that cannot be altered by management. Here we determined whether forest structure or climate determines lichen diversity in the Bavarian Forest National Park in southeastern Germany, taking spatial variables into account. We investigated 517 single tree stems along 4 transects in 113 pre-stratified plots (8 m in diameter) in this montane forest. We grouped environmental variables into three sets: climate (macroclimate, non-manageable), forest structure (manageable), and space. The explanatory powers of these sets of variables for lichen diversity were compared using variance partitioning for the lichen community, species density, and threatened species density. The relationships of single characteristics of forest structure with lichen species diversity were analyzed using generalized linear models (GLM). Lichen diversity was better explained by stand structures than by climate. Spatial effects influenced the number of species per plot. Among the structural features, the availability of dead wood and sycamore maple as well as forest continuity were most important for the enhancement of lichen diversity. Open canopy structures affected the total diversity positively. Although the availability of large trees was not an influential factor in the GLM at the plot level, high diversity levels were generally associated with large stem diameters at the level of single stems. We provide recommendations for sustainable forest-management practices that aim at specifically enhancing lichen diversity in temperate areas experiencing low levels of air pollution.