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Changes in agroecosystem management (e.g. landscape diversity, management intensity) affect the natural control of pests. The effects of agricultural change on this ecosystem service, however, are not universal and the mechanisms affecting it remain to be understood. As biological control is effectively the product of networks of interactions between pests and their natural enemies, food web analysis provides a versatile tool to address this gap of knowledge. The proposed project will utilize a molecular food web approach and examine, for the first time, how changes in plant fertilisation and landscape complexity affect quantitative aphid-parasitoid-hyperparasitoid food webs on a species-specific level to unravel how changes in food web interactions affect parasitoid aphid control. Based on the fieldderived data, cage experiments will be conducted to assess how parasitoid diversity and identity affect parasitoid interactions and pest control, complementing the field results. The work proposed here will take research on parasitoid aphid control one step further, as it will provide a clearer understanding of how plant fertilization affects whole aphid-parasitoid food webs in both simple and complex landscapes, allowing for further improvements in natural pest control.
Chromium (Cr) is introduced into the environment by several anthropogenic activities. A striking ex-ample is the area around Kanpur in the Indian state of Uttar Pradesh, where large amounts of Cr-containing wastes have been recently illegally deposited. Hexavalent Cr, a highly toxic and mobile contaminant, is present in significant amounts in these wastes, severely affecting the quality of sur-roundings soils, sediments, and ground waters. The first major goal of this study is to clarify the solid phase speciation of Cr in these wastes and to examine its leaching behavior. X-ray diffraction and synchrotron-based X-ray absorption spectroscopy techniques will be employed for quantitative solid phase speciation of Cr. Its leaching behavior will be studied in column experiments performed at un-saturated moisture conditions with flow interruptions simulating monsoon rain events. Combined with geochemical modeling, the results will allow the evaluation of the leaching potential and release kinetics of Cr from the waste materials. The second major goal is to investigate the spatial distribution, speciation, and solubility of Cr in the rooting zone of chromate-contaminated soils surrounding the landfills, and to study the suitability of biochar as novel soil amendment for mitigating the deleterious effects of chromate pollution. Detailed field samplings and laboratory soil incubation studies will be carried out with two agricultural soils and biochar from the Kanpur region.
Farm structures are often characterized by regional heterogeneity, agglomeration effects, sub-optimal farm sizes and income disparities. The main objective of this study is to analyze whether this is a result of path dependent structural change, what the determinants of path dependence are, and how it may be overcome. The focus is on the German dairy sector which has been highly regulated and subsidized in the past and faces severe structural deficits. The future of this sector in the process of an ongoing liberalization will be analyzed by applying theoretical concepts of path dependence and path breaking. In these regards, key issues are the actual situation, technological and market trends as well as agricultural policies. The methodology will be based on a participative use of the agent-based model AgriPoliS and participatory laboratory experiments. On the one hand, AgriPoliS will be tested as a tool for stakeholder oriented analysis of mechanisms, trends and policy effects. This part aims to analyze whether and how path dependence of structural change can be overcome on a sector level. In a second part, AgriPoliS will be extended such that human players (farmers, students) can take over the role of agents in the model. This part aims to compare human agents with computer agents in order to overcome single farm path dependence.
Subproject 3 will investigate the effect of shifting from continuously flooded rice cropping to crop rotation (including non-flooded systems) and diversified crops on the soil fauna communities and associated ecosystem functions. In both flooded and non-flooded systems, functional groups with a major impact on soil functions will be identified and their response to changing management regimes as well as their re-colonization capability after crop rotation will be quantified. Soil functions corresponding to specific functional groups, i.e. biogenic structural damage of the puddle layer, water loss and nutrient leaching, will be determined by correlating soil fauna data with soil service data of SP4, SP5 and SP7 and with data collected within this subproject (SP3). In addition to the field data acquired directly at the IRRI, microcosm experiments covering the broader range of environmental conditions expected under future climate conditions will be set up to determine the compositional and functional robustness of major components of the local soil fauna. Food webs will be modeled based on the soil animal data available to gain a thorough understanding of i) the factors shaping biological communities in rice cropping systems, and ii) C- and N-flow mediated by soil communities in rice fields. Advanced statistical modeling for quantification of species - environment relationships integrating all data subsets will specify the impact of crop diversification in rice agro-ecosystems on soil biota and on the related ecosystem services.
It is well established that reduced supply of fresh organic matter, interactions of organic matter with mineral phases and spatial inaccessibility affect C stocks in subsoils. However, quantitative information required for a better understanding of the contribution of each of the different processes to C sequestration in subsoils and for improvements of subsoil C models is scarce. The same is true for the main controlling factors of the decomposition rates of soil organic matter in subsoils. Moreover, information on spatial variabilities of different properties in the subsoil is rare. The few studies available which couple near and middle infrared spectroscopy (NIRS/MIRS) with geostatistical approaches indicate a potential for the creation of spatial maps which may show hot spots with increased biological activities in the soil profile and their effects on the distribution of C contents. Objectives are (i) to determine the mean residence time of subsoil C in different fractions by applying fractionation procedures in combination with 14C measurements; (ii) to study the effects of water content, input of 13C-labelled roots and dissolved organic matter and spatial inaccessibility on C turnover in an automatic microcosm system; (iii) to determine general soil properties and soil biological and chemical characteristics using NIRS and MIRS, and (iv) to extrapolate the measured and estimated soil properties to the vertical profiles by using different spatial interpolation techniques. For the NIRS/MIRS applications, sample pretreatment (air-dried vs. freeze-dried samples) and calibration procedures (a modified partial least square (MPLS) approach vs. a genetic algorithm coupled with MPLS or PLS) will be optimized. We hypothesize that the combined application of chemical fractionation in combination with 14C measurements and the results of the incubation experiments will give the pool sizes of passive, intermediate, labile and very labile C and N and the mean residence times of labile and very labile C and N. These results will make it possible to initialize the new quantitative model to be developed by subproject PC. Additionally, we hypothesize that the sample pretreatment 'freeze-drying' will be more useful for the estimation of soil biological characteristics than air-drying. The GA-MPLS and GA-PLS approaches are expected to give better estimates of the soil characteristics than the MPLS and PLS approaches. The spatial maps for the different subsoil characteristics in combination with the spatial maps of temperature and water contents will presumably enable us to explain the spatial heterogeneity of C contents.
Sekundäre Partikelneubildung ist eine Hauptquelle für atmosphärische Partikel mit wichtigen Folgen für das Klima und die menschliche Gesundheit. Dieses Vorhaben untersucht die Rolle von Luft Ionen bei der sekundären Partikelneubildung in Flussreaktor- und Aerosolkammer-Experimenten unter kontrollierten Laborbedingungen. Trotz beträchtlicher Fortschritte in der Messtechnik zur Untersuchung der atmosphärischen Nukleation und des Partikelwachstums bestehen weiterhin Verständnislücken hinsichtlich der grundlegenden physikalischen und chemischen Prozesse. Insbesondere die möglichen Effekte von Ionen-Partikel-Wechselwirkungen und von Ionenchemie auf die Partikelneubildung werden kontrovers diskutiert. In Ergänzung zu bestehenden Forschungsprogrammen hinsichtlich der Rolle von Ionen im initialen Nukleationsschritt wird vorgeschlagen, Ionen-Partikel-Wechselwirkungen während des anschließenden Partikelwachstums zu untersuchen und sich dabei auf direkte Messungen des Ladungszustands, der Wachstumsraten und der chemischen Zusammensetzung von sekundärem organischem Aerosol zu konzentrieren. Hierzu werden der Ladungszustand und die Wachstumsraten von Partikelpopulationen mit einem modifizierten Mobilitätspartikelspektrometer unter wohldefinierten Randbedingungen in Laborexperimenten quantifiziert. In einem nächsten Schritt werden die neuartigen Messmöglichkeiten unseres Aerosol-Massenspektrometers CAChUP voll ausgeschöpft, um den Beitrag verschiedener organischer Vorläufergase zur chemischen Zusammensetzung von sekundärem organischen Aerosol bei variierenden Ladungszuständen zu quantifizieren. Schließlich werden die Ergebnisse dieser Experimente durch Messungen zur sekundären organischen Partikelbildung bei wohldefinierten Ionenkonzentrationen an einer Aerosolkammer überprüft. Die vorgeschlagene Forschungsagenda ist somit darauf abgestimmt, mögliche ladungs-katalysierte chemische Mechanismen bei der sekundären Aerosolbildung besser einzuordnen.
We are currently facing the urgent need to improve our understanding of carbon cycling in subsoils, because the organic carbon pool below 30 cm depth is considerably larger than that in the topsoil and a substantial part of the subsoil C pool appears to be much less recalcitrant than expected over the last decades. Therefore, small changes in environmental conditions could change not only carbon cycling in topsoils, but also in subsoils. While organic matter stabilization mechanisms and factors controlling its turnover are well understood in topsoils, the underlying mechanisms are not valid in subsoils due to depth dependent differences regarding (1) amounts and composition of C-pools and C-inputs, (2) aeration, moisture and temperature regimes, (3) relevance of specific soil organic carbon (SOC) stabilisation mechanisms and (4) spatial heterogeneity of physico-chemical and biological parameters. Due to very low C concentrations and high spatio-temporal variability of properties and processes, the investigation of subsoil phenomena and processes poses major methodological, instrumental and analytical challenges. This project will face these challenges with a transdisciplinary team of soil scientists applying innovative approaches and considering the magnitude, chemical and isotopic composition and 14C-content of all relevant C-flux components and C-fractions. Taking also the spatial and temporal variability into account, will allow us to understand the four-dimensional changes of C-cycling in this environment. The nine closely interlinked subprojects coordinated by the central project will combine field C-flux measurements with detailed analyses of subsoil properties and in-situ experiments at a central field site on a sandy soil near Hannover. The field measurements are supplemented by laboratory studies for the determination of factors controlling C stabilization and C turnover. Ultimately, the results generated by the subprojects and the data synthesized in the coordinating project will greatly enhance our knowledge and conceptual understanding of the processes and controlling factors of subsoil carbon turnover as a prerequisite for numerical modelling of C-dynamics in subsoils.
LA-ICP-MS data from three different experiments including five foraminiferal species: Ammonia confertitesta (Bourgenuf, France), Bulimina marginata, Cassidulina laevigata (Gullmard Fjord, Sweden), Amphistegina lessonii and Operculina ammonoides (Eilat, Israel). Foraminifera were cultured at different oxygen concentrations (30% and 100% oxygen saturation). Element to calcium ratio (E/Ca) and partition coefficients (D) of Mg, Mn and Sr are noted for individual laser ablation measurements per specimen.
Vorkommen, Häufigkeit, chemische Zusammensetzung und Mischungszustand jener Aerosolpartikel in der Erdatmosphäre, an denen sich durch heterogene Nukleation in unterkühlten Wolken Eis bilden kann (Ice Nucleating Particles = INP), werden experimentell untersucht. Diese Informationen sind wichtig für das Verständnis der Niederschlagsbildung, und finden in parametrisierter Form Eingang in meteorologische Modelle zur Vorhersage des Niederschlages. Das Projekt verwendet hierbei im Wesentlichen physikalische Methoden zur Identifikation und Isolation der Partikel aus der Atmosphäre, und nachfolgend elektronenmikroskopische Methoden zur mineralogischen Analyse einzelner Partikel. Die Identifikation jener wenigen Aerosolpartikel (ca. 1 von 10.000 bis 1 von 100.000), die Eisbildungsfähigkeit besitzen, erfolgt, indem eine Aerosolprobe einer Unterkühlung unter 0°C und Wasserdampfübersättigung ausgesetzt wird, und die an INP entstehenden Eiskristalle fotografiert und gezählt werden. Es werden sowohl Aerosolpartikel aus luftgetragenem Aerosol untersucht (aus dem Eiskeimzähler FINCH) wie auch Partikel, die aus einer Luftprobe auf einem Silizium-Probenträger niedergeschlagen und danach als INP identifiziert wurden (Eiskeimzähler FRIDGE). Eine dritte und vierte Methode (Ice-CVI und ISI) isolieren eisbildungsfähige Partikel, indem aus einer angesaugten Probe von Wolkenluft die Eiskristalle strömungstechnisch von den übrigen Luftbestandteilen getrennt werden. Alle Eiskeimproben werden im Rasterelektronenmikroskop auf Größe, Morphologie, Mischungszustand und chemische Zusammensetzung untersucht und die Ergebnisse der verschiedenen Ansätze verglichen. In Feldexperimenten werden Atmosphärenproben verschiedener geographischer Provenienz (Mitteleuropa, Forschungsstation Jungfraujoch, Wüstenstaub, Vulkanstaub) erhalten. In Laborexperimenten wird mit vorher gesammelt und charakterisierten Modellsubstanzen gearbeitet. Weiterhin wird durch tägliche Messungen der Anzahl-Konzentration und Zusammensetzung von Eiskeimen am Taunus Observatorium nahe Frankfurt über einen längeren Zeitraum untersucht, ob es Saisonalitäten, bevorzugte Quellgebiete (z.B. Wüsten, Industrie, etc.) und biologische Einflussfaktoren (z.B. Pollen, Pflanzenabrieb, Bakterien) für das Vorkommen von Eisnuklei gibt.
Soil organic matter (SOM) controls large part of the processes occurring at biogeochemical interfaces in soil and may contribute to sequestration of organic chemicals. Our central hypothesis is that sequestration of organic chemicals is driven by physicochemical SOM matrix aging. The underlying processes are the formation and disruption of intermolecular bridges of water molecules (WAMB) and of multivalent cations (CAB) between individual SOM segments or between SOM and minerals in close interaction with hydration and dehydration mechanisms. Understanding the role of these mediated interactions will shed new light on the processes controlling functioning and dynamics of biogeochemical interfaces (BGI). We will assess mobility of SOM structural elements and sorbed organic chemicals via advanced solid state NMR techniques and desorption kinetics and combine these with 1H-NMR-Relaxometry and advanced methods of thermal analysis including DSC, TGADSC- MS and AFM-nanothermal analysis. Via controlled heating/cooling cycles, moistening/drying cycles and targeted modification of SOM, reconstruction of our model hypotheses by computational chemistry (collaboration Gerzabek) and participation at two larger joint experiments within the SPP, we will establish the relation between SOM sequestration potential, SOM structural characteristics, hydration-dehydration mechanisms, biological activity and biogechemical functioning. This will link processes operative on the molecular scale to phenomena on higher scales.
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