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There is much interest in the identification of the main drivers controlling changes in the microbial community that may be related to sustainable land use. We examined the influence of soil properties and land-use intensity (N fertilization, mowing, grazing) on total phospholipid fatty acid (PLFA) biomass, microbial community composition (PLFA profiles) and activities of enzymes involved in the C, N, and P cycle. These relationships were examined in the topsoil of grasslands from three German regions (Schorfheide-Chorin (SCH), Hainich-Dun (HAI), Schwabische Alb (ALB)) with different parent material. Differences in soil properties explained 60% of variation in PLFA data and 81% of variation in enzyme activities across regions and land-use intensities. Degraded peat soils in the lowland areas of the SCH with high organic carbon (OC) concentrations and sand content contained lower PLFA biomass, lower concentrations of bacterial, fungal, and arbuscular mycorrhizal PLFAs, but greater enzyme activities, and specific enzyme activities (per unit microbial biomass) than mineral soils in the upland areas of the HAI and ALB, which are finer textured, drier, and have smaller OC concentrations. After extraction of variation that originated from large-scale differences among regions and differences in land-use intensities between plots, soil properties still explained a significant amount of variation in PLFA data (34%) and enzyme activities (60%). Total PLFA biomass and all enzyme activities were mainly related to OC concentration, while relative abundance of fungi and fungal to bacterial ratio were mainly related to soil moisture. Land-use intensity (LUI) significantly decreased the soil C:N ratio. There was no direct effect of LUI on total PLFA biomass, microbial community composition, N and P cycling enzyme activities independent of study region and soil properties. In contrast, the activities and specific activities of enzymes involved in the C cycle increased significantly with LUI independent of study region and soil properties, which can have impact on soil organic matter decomposition and nutrient cycling. Our findings demonstrate that microbial biomass and community composition as well as enzyme activities are more controlled by soil properties than by grassland management at the regional scale.
This study examines how often and in which form students use the option of gradeskipping in Germany and what characterizes those students. The database was derived from a sample of N = 4,103 students (grades 8-10), who were tested within the standardisation process of the national educational standards in mathematics. For these students data existed on their mathematical competence (educational standard items) and intelligence (subtests word analogies and figural analogies of the KFT 4-12 + R). Furthermore, we identified n = 33 (0,8%) students by questionnaire, who had already skipped one grade. Those accelerated students are predominantly boys, had skipped the grade during their first years at school and performed only slightly above-average on two cognitive ability scales. At the time the survey was conducted, 39% did not attend a Gymnasium and 34 % had to repeat one grade after having been accelerated. While they report average grades in relation to their peers, their mathematical competence is well above average.
The present study investigates school context effects on psychosocial characteristics (academic self-concept, peer relations, school satisfaction, and school anxiety) of high-achieving and gifted students. Students who did or did not make an early transition from elementary to secondary schools for high-achieving and gifted students in 5th grade in Berlin, Germany, are compared in their psychosocial development. The sample comprises 155 early-entry students who moved to an academically selective secondary school (Gymnasium) and 3,169 regular students who remained in elementary school until the end of 6th grade. Overall, a complex pattern of psychosocial development emerged for all students, with both positive and negative outcomes being observed. Specifically, the transition into academically selective learning environments seemed to come at some cost for psychosocial development. Propensity score matching analysis isolating the effects of selective school intake and the school context effect itself revealed negative contextual effects of early transition to Gymnasium on academic self-concept and school anxiety; additionally, the positive trend in peer relations observed among regular students was not discernible among early-entry students.
Using German data, we examined the effects of one specific type of acceleration-grade skipping-on academic performance. Prior research on the effects of acceleration has suffered from methodological restrictions, especially due to a lack of appropriate comparison groups and a priori measurements. For this reason, propensity score matching was applied in this analysis to minimize selection bias due to observed confounding variables. Various types of matching were attempted, and, in consideration of balancing the covariates, full matching was the final choice. We used data from the Berlin ELEMENT Study, analyzing, after matching, the information of 81 students who had skipped a grade over the course of elementary school and up to 1,668 nonaccelerated students who attended the same grade level as the accelerated students. Measurements took place 3 times between the 4th and 6th grades, including the assessment of reading, spelling, and mathematics performance. After matching, the results of between-group comparisons regarding performance indices showed no significant effects of skipping a grade, other than a small positive effect found on spelling performance. Theoretical implications and methodological limitations are discussed.