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Neue Veröffentlichungen:
Critical analysis of socio-natural dynamics driven by the agricultural commodity boom: the case of Hass avocado in northern Caldas, Colombia
(2025) Suarez, Andres
This explanatory study investigates the expansion of Hass avocado plantations (HAP) and their transformative impact on the socio-natural dynamics in Salamina, Caldas, Colombia. The central research question—Why are Hass avocado plantations expanding and transforming the socio-natural dynamics in the Global South?—is addressed through a systematic approach grounded in interdisciplinary frameworks and methods.
To address this overarching question, a robust theoretical framework was first developed to analyze the socio-natural interactions underlying these transformations. The study then employed four sub-questions to explore the issue systematically. The first sub-question examined the phenomenon from a Global South perspective, followed by two sub-questions focusing on the specifics of the Salamina case. The final sub-question recontextualized the findings within the broader global transformations of food systems, offering insights into the dynamics of these changes as part of a larger learning process.
This interdisciplinary research is underpinned by Critical Realism, integrating theoretical and conceptual approaches from political ecology, critical resource geography, and critical political economy. A multilevel design was utilized to address the four sub-questions, employing tailored sub-designs for each. The study’s overarching objective was explanatory: not only to elucidate the socio-economic and environmental implications of HAP expansion but also to analyze the socio-historical, economic, and political structures enabling this phenomenon.
Methodologically, a mixed-methods approach was employed through a sequential design, balancing qualitative and quantitative data collected and analyzed simultaneously before integration during interpretation. A single cross-sectional explanatory case study further deepened the analysis.
Findings reveal a complex landscape of socio-economic and environmental dynamics in Colombia’s HAP sector. While the plantations have driven economic growth and employment in Salamina and Caldas, they have also introduced significant environmental and social challenges. Colombia faces a critical juncture where economic development must align with environmental sustainability and social responsibility. Policymakers, environmental agencies, and the agricultural community must act decisively to achieve this balance, leveraging the economic potential of Hass avocados while safeguarding ecological systems and cultural heritage. The development and enforcement of sustainable public policies will be essential to navigating this multifaceted challenge.
Verborgene Schätze – Eine Uhrmacherhandschrift aus dem 18. Jahrhundert
(2025) Schneider, Olaf
Stoffeigenschaften und Umweltverhalten von Ivermectin und anderen Antiparasitika im One Health-Kontext: Interdisziplinäre Herausforderungen für den Bodenschutz
(2025) Heinrich, Andre Patrick
Die kumulative Dissertation untersucht die Stoffeigenschaften und das Umweltverhalten des Veterinär-Antiparasitikums Ivermectin und weiterer verwandter Wirkstoffe. Ziel ist es, die Umweltrisiken dieser Substanzen aus einer One Health Perspektive zu betrachten. Diese strebt die ganzheitliche Betrachtung der Zusammenhänge zwischen menschlicher Gesundheit, Tiergesundheit und Umweltschutz an. Die Wirkstoffe gehören zur Gruppe der makrozyklischen Laktone, die in Human- und Veterinärmedizin sowie im Pflanzenschutz zur Kontrolle von Schadorganismen verwendet werden. Zunehmend wird auch ein Einsatz in der Vektorkontrolle diskutiert. Der breite Einsatz der Wirkstoffe wirft daher Fragen nach der Vereinbarkeit von Gesundheitszielen und Umweltschutz im Sinne von One Health auf.
Planen - Unterstützen - Durchführen: Fortbildungen in Volkshochschul-Verbandsstrukturen
(2025) Nistal, Lydia Johanna
Die Verbänden der Volkshochschulen und ihren stadtstaatlichen Zusammenschlüsse sind wichtige Akteure in der Erwachsenen- und Weiterbildung. Sie führen die politische Interessenvertretung ihrer Mitglieder aus, erbringen Dienstleistungen und sind an Forschung und Zeitschriftenwesen in der Erwachsenen- und Weiterbildung beteiligt.
Als Forschungsgegenstand sind sie dagegen erst sporadisch erschlossen.
Anhand recherchierter Forschungsdesiderate erforscht die Dissertation in einem qualitativen Vorgehen verbandliche Funktionen in Volkschochschul-Verbandsstrukturen. Dabei wird ein besonderer Fokus auf Fortbildungen gelegt, die für die Mitglieder und ihr Personal entwickelt, angeboten und durchgeführt werden. Hierbei zeigen sich mehrere Varianten der Zusammenarbeit zwischen den Verbänden, ihren Mitgliedern und weiteren Akteuren aus dem Organisationalen Feld in verschiedenen Konstellationen.
Trapped, Released, Transformed: How Minerals Shape the Cycling of Organic Matter in Soils
(2025) Konrad, Alexander
Soil organic carbon persistence arises from the intertwined effects of mineral surfaces, microbial activity, and the chemical structure of organic matter, which is further modulated by a soil´s boundary conditions. This dissertation addresses two linked questions: How do minerals govern soil organic matter adsorption and desorption, and how do these organo-mineral interactions feed back on microbial utilization and persistence of mineral-associated organic carbon?
To probe these questions, calorimetry was combined with isotope tracing and mineral long-term field exposure studies. Isothermal titration calorimetry provided the first direct thermodynamic quantification of adsorption of organic acids to mineral surface, showing that salicylic acid and citric acids bind exothermically to goethite. Calorimetry adsorption experiments onto goethite with differing lattice defect densities uncovered intensified exothermic binding and a greater loss of entropy on minerals abundant with defects, highlighting that adsorption thermodynamics can differ even for a single mineral type substantially. To connect mineral control of organic matter sorption with its microbial fate, uniformly and carboxyl-radiocarbon labeled monomers were adsorbed onto kaolinite, illite and goethite in a set of batch sorption experiments and incubated in loamy and sandy arable topsoil. Despite strong inner-sphere complexation, a substantial share of ligand-bound carboxyl carbon was mineralized.
At the molecular scale, microbial carbon use efficiency (CUE) of mineral-adsorbed monomers rose linearly with desorbability (i.e., the ratio of the amount desorbed to the amount sorbed) across all investigated compounds. Notably, CUE values were consistently lower for monomers bound to goethite than to the clay minerals. Taken together, these findings show that mineral surface properties and sorption-desorption dynamics can redirect metabolic allocation between biomass synthesis and respiratory loss. Recognizing that minerals alter nutrient availability in soil, the dissertations research extended to cover phosphorus dynamics as well. In incubation studies, goethite-amended soil´s strong immobilization of phosphate constrained microbial growth, which channeled metabolism toward higher respiration and lower CUE, while illite did not immobilize phosphorus, resulting in higher CUEs for mineral-adsorbed monomers.
Conversely, studying phosphorus transport in forest ecosystems exposed that soil colloids rich in carbon and iron can deliver large quantities of bioavailable phosphorus into sinks mimicking plant roots. This demonstrates that organo-mineral associations can alternate between acting as phosphorus sinks and nutrient shuttles, depending on their saturation state and soil boundary conditions. Laboratory findings on mineral-associated organic matter cycling were further validated under field conditions investigating minerals buried in temperate grassland and forests for five years. Across all sites, goethite accrued nearly four times more carbon than illite, while the proportion of microbial biomass on mineral-associated organic carbon was higher on illite. Notably, carbon-, nitrogen-, and phosphorus-acquiring enzymes were significantly higher on goethite than illite or the surrounding soil, characteristic of microbial mining under nutrient limitations.
Three overarching insights emerge. First, the amount of carbon stabilized on mineral surfaces is mineral-specific and further depends on molecular functionality and soil properties such as pH and phosphate accessibility, but no sorption-strength threshold dictates bioaccesibility. Second, microbial processing of mineral-associated organic carbon is inseparable from phosphorus cycling, both of which are mediated by mineral type. Third, oxides and clay minerals both contribute to the persistence of organic carbon, but via contrasting mechanisms. Illite´s nutrient-rich surfaces promote rapid turnover with high CUE that channels carbon into new biomass, whereas goethite traps larger amounts in forms less accessible to microbes, leaving the small bioavailable fraction prone to respiration. Together, these findings refine our understanding of how minerals govern organic matter turnover and nutrient availability in soil: their role is soil specific, affected by pH, nutrient availability, and land use.