Selbsteinschätzungen von Schülern zum Sozial- und Lernverhalten - Erfassung, Struktur und Analyse von Schülerselbstkonzepten und schulischem Problemverhalten

The present doctoral thesis deals with the assessment, structure, and analysis of self-concepts of students for school-related social and learning behavior based on three empirical studies. The first study examines self-concepts of fourth graders and reveals that children at this age have specific self-concepts that are mainly valid and closely related to grades in mathematics and German. In addition, regression analysis indicate that good grades in mathematics are associated with high self-concepts in cooperation, self-control, endurance, concentration and diligence in learning. Moreover, good grades in German can be explained by high self-concepts in cooperation and concentration. The second study investigates gender differences in self-concepts for school-related social and learning behavior as well as in grades in mathematics and German. Boys score lower in almost all facets of school-related social and learning behavior and achieve lower grades in German than girls. Furthermore, both grades in mathematics and German are linked with high self-concepts in cooperation, endurance and concentration as well as with high class average grades in these two subjects. However, low assessments in care for learning and a migration background have a negative impact on these two grades. The third study analyses specific relations between reactive/proactive aggression and social-emotional skills in self-concepts of students. Regression analysis indicate that both types of aggression can be explained by low perceived skills (self-control, self-assertion). In addition, reactive aggression is associated with a high perceived empathy

Gene expression changes in the coccolithophore Emiliania huxleyi after 500 generations of selection to ocean acidification

Coccolithophores are unicellular marine algae that produce biogenic calcite scales and substantially contribute to marine primary production and carbon export to the deep ocean. Ongoing ocean acidification particularly impairs calcifying organisms, mostly resulting in decreased growth and calcification. Recent studies revealed that the immediate physiological response in the coccolithophore Emiliania huxleyi to ocean acidification may be partially compensated by evolutionary adaptation, yet the underlying molecular mechanisms are currently unknown. Here, we report on the expression levels of 10 candidate genes putatively relevant to pH regulation, carbon transport, calcification and photosynthesis in E. huxleyi populations short-term exposed to ocean acidification conditions after acclimation (physiological response) and after 500 generations of high CO2 adaptation (adaptive response). The physiological response revealed downregulation of candidate genes, well reflecting the concomitant decrease of growth and calcification. In the adaptive response, putative pH regulation and carbon transport genes were up-regulated, matching partial restoration of growth and calcification in high CO2-adapted populations. Adaptation to ocean acidification in E. huxleyi likely involved improved cellular pH regulation, presumably indirectly affecting calcification. Adaptive evolution may thus have the potential to partially restore cellular pH regulatory capacity and thereby mitigate adverse effects of ocean acidification

Functional ecology of tropical forest recovery

Electronic abstract of the thesis for the library for the acquisitions department of Wageningen UR library (published as a html file so hyperlinks may be included) In English, one or 2 pages. Functional ecology of tropical forest recovery Currently in the tropics, the area of secondary forest exceeds that of mature forest, and the importance of secondary forest will probably continue to increase in the future. Understanding secondary forests’ potential for maintaining biodiversity and critical ecosystem functions is thereby vital. The aim of this study was to mechanistically link tropical forest succession with the recovery of ecosystem functioning after agricultural field abandonment using a trait-based approach. Such an approach makes use of functional traits; components of an organism’s phenotype that are key to assess ecosystem responses to global change drivers, and are at the same time indicators of how organisms drive changes in ecosystem functioning. Trait-based approaches could therefore provide a mechanistic way to scale up from organisms to ecosystems and thereby contribute towards a more predictive biodiversity and ecosystem functioning science. For this study, I made use of secondary forest data from a wet forest region in Chiapas (main study site), that cover the first 3 decades of succession, complemented with data from a dry forest region in Oaxaca, that cover the first 6 decades of succession. Both are tropical regions in Mexico, characterized by high biodiversity levels and rapid forest loss for agricultural expansion. In this study I found that functional diversity (the range of different functional traits) increases rapidly and functional composition (the weighted average functional trait value) changes directionally with succession (chapter 2 and 3). These reflect changing habitat filters (changing environmental gradients that underlie succession), and also a gradual shift from habitat filtering towards an increasing effect of competitively driven limiting trait similarity (chapter 4 and 5). Such successional changes in community functional properties suggest strong changes in ecosystem functions, however in situ ecosystem function rates were primarily explained by the total amount of biomass present rather than by biodiversity or functional trait properties of secondary forests (chapter 6). Only the more controlled ex situ decomposition rates were additionally significantly influenced by functional diversity and functional composition. When evaluating the identity of species that drive most of the ecosystem functions I found that different functions were largely driven by the same (dominant) species, implying a limited effect of biodiversity for multifunctionality at a given moment in time. This suggests that biodiversity is mainly important for maintaining multifunctional ecosystems across temporal and spatial scales (chapter 7). Deforestation is a major threat to natural forests and biodiversity, and I recognize that secondary forests are generally a poor substitute of mature forest. Nevertheless, I show that unassisted recovery through natural succession can be rapid, and contribute considerably to maintenance of biodiversity, functional strategies and ecosystem functions. So while protecting the remaining tracts of mature forests is vital, secondary forests are key components of multifunctional human-modified landscapes where synergies between biodiversity, ecosystem functions and human wellbeing can be optimized.</p

Long-term dynamics of adaptive evolution in a globally important phytoplankton species to ocean acidification

Marine phytoplankton may adapt to ocean change, such as acidification or warming, because of their large population sizes and short generation times. Long-term adaptation to novel environments is a dynamic process, and phenotypic change can take place thousands of generations after exposure to novel conditions. We conducted a long-term evolution experiment (4 years = 2100 generations), starting with a single clone of the abundant and widespread coccolithophore Emiliania huxleyi exposed to three different CO2 levels simulating ocean acidification (OA). Growth rates as a proxy for Darwinian fitness increased only moderately under both levels of OA [+3.4% and +4.8%, respectively, at 1100 and 2200 μatm partial pressure of CO2 (Pco2)] relative to control treatments (ambient CO2, 400 μatm). Long-term adaptation to OA was complex, and initial phenotypic responses of ecologically important traits were later reverted. The biogeochemically important trait of calcification, in particular, that had initially been restored within the first year of evolution was later reduced to levels lower than the performance of nonadapted populations under OA. Calcification was not constitutively lost but returned to control treatment levels when high CO2–adapted isolates were transferred back to present-day control CO2 conditions. Selection under elevated CO2 exacerbated a general decrease of cell sizes under long-term laboratory evolution. Our results show that phytoplankton may evolve complex phenotypic plasticity that can affect biogeochemically important traits, such as calcification. Adaptive evolution may play out over longer time scales (>1 year) in an unforeseen way under future ocean conditions that cannot be predicted from initial adaptation responses

Between- and within-population variations in thermal reaction norms of the coccolithophore Emiliania huxleyi

Thermal reaction norms for growth rates of six Emiliania huxleyi isolates originating from the central Atlantic (Azores, Portugal) and five isolates from the coastal North Atlantic (Bergen, Norway) were assessed. We used the template mode of variation model to decompose variations in growth rates into modes of biological interest: vertical shift, horizontal shift, and generalist–specialist variation. In line with the actual habitat conditions, isolates from Bergen (Bergen population) grew well at lower temperatures, and isolates from the Azores (Azores population) performed better at higher temperatures. The optimum growth temperature of the Azores population was significantly higher than that of the Bergen population. Neutral genetic differentiation was found between populations by microsatellite analysis. These findings indicate that E. huxleyi populations are adapted to local temperature regimes. Next to between-population variation, we also found variation within populations. Genotype-by-environment interactions resulted in the most pronounced phenotypic differences when isolates were exposed to temperatures outside the range they naturally encounter. Variation in thermal reaction norms between and within populations emphasizes the importance of using more than one isolate when studying the consequences of global change on marine phytoplankton. Phenotypic plasticity and standing genetic variation will be important in determining the potential of natural E. huxleyi populations to cope with global climate change

Drivers of field-saturated soil hydraulic conductivity: Implications for restoring degraded tropical landscapes

Water security represents a major challenge in East Africa, affecting the livelihoods of millions of people and hindering sustainable development. Predicted increases in rainfall intensity and variability are expected to exacerbate water insecurity and land degradation. Improving soil infiltrability is an effective strategy for addressing water insecurity and land degradation. Research on soil infiltrability is often highly localized; therefore, scientific understanding of the drivers of infiltrability on larger spatial scales is limited. The aim of this study was to understand the main drivers of infiltrability across five contrasting landscapes in Kenya. We measured field-saturated hydraulic conductivity (Kfs) in 257 plots and collected data for variables representing soil properties (sand content, soil organic carbon (SOC) and pH), land degradation (grazing pressure and presence of erosion), vegetation quantity (woody aboveground biomass), and vegetation quality (functional properties and diversity). We used generalized mixed-effects models to test for the effects of these variables on Kfs. Median Kfs for the five sites ranged between 23.8 and 101.8 mm h−1. We found that Kfs was positively associated with sand content (standardized effect 0.39), SOC content (0.15), and functional diversity of woody vegetation (0.09), while it had a negative relationship with the presence of erosion (−0.24) and grazing pressure (−0.09). Subsequently, we conclude that infiltrability can be enhanced through using land restoration strategies which specifically target parameters that affect Kfs. The results further support that Kfs is not solely dictated by inherent soil properties, and that management interventions which boost SOC, reduce erosion, and minimize unsustainable grazing can help address water scarcity by restoring soil hydrological function

Review of Methodologies for Land Degradation Neutrality Baselines: Sub-National case studies from Costa Rica and Namibia

The objective of this report is to identify entry points and challenges for subnational LDN baselines in order to inform subnational planning processes as potential vehicle for the implementation of LDN targets on the ground. For this purpose two focus regions were chosen within two of the countries – namely Namibia and Costa Rica – that participated in the first LDN pilot phase. The focus areas in Namibia and Costa Rica are the regions of Otjozondjupa and Rio Jesus Maria watershed respectively. Both Namibia and Costa Rica provide interesting case studies given the differences in types of land degradation, national capacities, and land resources