Peroxyradikale sind kurzlebige Spezies, die an den meisten Oxidationsprozessen in der Atmosphäre beteiligt sind, die zur Bildung von langlebigeren und chemisch oder toxikologisch wichtigen Schadstoffen wie Ozon führen. Insbesondere in Gebieten, die von komplexen Emissionsquellen betroffen sind, sind Peroxyradikal-Messmethoden mit ausreichender Genauigkeit, Reproduzierbarkeit und Empfindlichkeit erforderlich, um die chemische Umwandlung der städtischen Umweltverschmutzung zu verstehen. In dieser Hinsicht ermöglichen Vergleiche von state-of-the-art Sensoren in chemischen Reaktorkammern deren Charakterisierung unter kontrollierten Bedingungen und verbessern das Vertrauen in die Messung von Peroxyradikalen.SPRUCE strebt ein besseres Verständnis der Rolle der Peroxyradikale bei atmosphärischen chemischen Umwandlungen an, die aus der Wechselwirkung zwischen urbanen anthropogenen und ländlichen biogenen Emissionen resultieren. Im Rahmen der vorgeschlagenen Arbeit wird das vorhandene PeRCEAS-Instrument (Peroxy Radical Chemical Enhancement and Absorption Spectrometer) an der Messkampagne des internationalen Projekts ACROSS (Atmospheric ChemistRy Of the Suburban Forest) zur Untersuchung des Schadstoffausflusses von Paris über ein Waldgebiet, und in der internationalen Vergleichsstudie ROxCOMP22 für wissenschaftliche Instrumente, die atmosphärische Peroxyradikale teilnehmen. Diese beiden Messkampagnen befassen sich mit zwei Hauptaspekten von SPRUCE. Sie bieten eine einzigartige Gelegenheit für a) die Messung von Peroxyradikalen in der spezifischen Umgebung von Interesse und in Verbindung mit einer umfangreichen Reihe von Beobachtungen, die für die Interpretation der Radikalchemie von wesentlicher Bedeutung sind, und b) die Bewertung der Datenqualität und Leistungsfähigkeit von PeRCEAS, insbesondere die Überprüfung der Sensitivität und Effizienz für die Speziation der Radikale unter kontrollierten Bedingungen.Ein Schwerpunkt der Studie wird auf der Untersuchung von Oxidationsreaktionen und Ozonausbeuten in Luftmassen mit unterschiedlicher anthropogener/biogener Signatur in Abhängigkeit von der Menge und Zusammensetzung von Peroxyradikalen liegen. Numerische Berechnungen und Modelle werden durch die Beobachtungen von Vorläuferspezies eingeschränkt, um die Budgets von Peroxyradikalen abzuschätzen. Der Vergleich mit den PeRCEAS-Messungen wird verwendet, um das Verständnis der Oxidationsmechanismen in urbanen Plumes gemischt mit biogenen Emissionen zu testen. Es wird erwartet, dass die Analyse des resultierenden Datensatzes das aktuelle Wissen über die chemische Transformation von Megacity-Emissionen während des atmosphärischen Transports ergänzt.
In recent years science has taken an increased interest in mineralization processes in tropical soils in particular under minimal tillage operations. Plant litter quality and management strongly affect mineralization-nitrification processes in soil and hence the fate of nitrogen in ecosystems and the environment. Plant secondary metabolites like lignin and polyphenols are poorly degradable and interact with proteins (protein binding capacity) and hence protect them from microbial attack. Nitrification, a microbiological process, directly and indirectly influences the efficiency of recovery of N in the vegetation as well as the loss of N (through denitrification and leaching) causing environmental pollution to water bodies and contributes to global warming (e.g. the greenhouse gas N2O is emitted as a by-product of nitrification and denitrification). Nitrifiers comprise a relatively narrow species diversity (at least as known to date) and are generally thought to be sensitive to low soil pH and stress. Despite these properties nitrification occurs in acid tropical soils with high levels of aluminium and manganese. Thus the main objective of the project will be the identification of micro-organisms and mechanisms responsible for mineralization-nitrification processes in acid tropical soils and the influence of long-term litter input of different chemical qualities and minimal tillage options. The project will include the use of stable isotopes (15N, 13C), mass spectrometry, gas chromatography (CO2, N2O), biochemical methods (PLFA) and molecular biology (16s rRNA., PCR, DGGE)
Verlässliche Vorhersagen von Wetter und Klimawandel erfordern ein gutes Verständnis der Eisbildung in troposphärischen Wolken. Von besonderer Bedeutung ist dabei die sogenannte heterogene Eisnukleation durch atmosphärische Aerosolpartikel. Das hier beantragte Projekt beinhaltet eine umfassende Untersuchung der heterogenen Eisnukleation in Zirruswolken und Mischphasenwolken, gemeinsam mit 8 weiteren Projekten der Forschergruppe INUIT. Eisbildung durch Kontaktgefrieren wird für einzelne Tröpfchen in einem elektrodynamischen Levitator (Paulfalle) untersucht. Experimente zum Einfluss von Aerosolen auf Immersionsgefrieren, Kontaktgefrieren und Depositionsnukleation werden in der AIDA-Wolkenkammer und einer neuen dynamischen Wolkenkammer durchgeführt, falls diese wie geplant bis Anfang 2016 zur Verfügung stehen wird. Hauptziele und Arbeitspakete des Projekts sind (a) Untersuchungen zum Immersionsgefrieren, Kontaktgefrieren und zur Depositionsnukleation von INUIT-2 Referenzaerosolen in enger Zusammenarbeit mit allen anderen lNUlT-2-Partnern, (b) AIDA-Wolkensimulationsexperimente mit redispergierten atmosphärischen Aerosolen die auf Filtern gesammelt wurden (in Zusammenarbeit mit RP8), (c) AIDA-Experimente mit porösen Partikeln zur Untersuchung des Einflusses von Kapillarkondensation und Prä-aktivierung auf Eisnukleationsprozesse, (d) EDB-Experimente zur Kontaktnukleation mit atmosphärisch relevanten und komplexen Aerosolen, (e) Untersuchungen zu den grundlegenden Mechanismen des Kontaktgefrierens, (f) die Entwicklung einer umfassenden und einheitlichen Parametrisierung heterogener Eisnukleation in enger Zusammenarbeit mit RP3 und RP5, (g) erste Experimente zur Kontaktnukleation in einer neuen Wolkenkammer unter Nutzung der Expertise aus langjährigen Experimenten zum Kontaktgefrieren und mit der Wolkensimulationskammer, (h) die Durchführung von zwei AIDA-Messkampagnen, eine nur für die INUIT-2- Partner und eine mit internationaler Beteiligung, bei denen Labormethoden und Feld Instrumente für die Messung von Aerosolen und eisbildenden Partikeln getestet und miteinander verglichen werden um hohe internationale Standards in der Eisnukleationsforschung zu entwickeln und zu erhalten. Die Aktivitäten an der AIDA-Wolkenkammer bieten auch eine gute Verknüpfung der Labor-, Feld und Modellieraktivitäten innerhalb der Forschergruppe INUIT und mit externen Partnern. In Ergänzung der laufenden INUIT-Arbeiten möchten wir in weiteren drei Jahren der Forschergruppe folgende neue Schwerpunkte setzen: die Eisnukleationseigenschaften von porösen Partikeln, Immersionsgefrieren und Depositionsnukleation von größenselektierten Partikeln mit Durchmessern bis zu einigen Mikrometern, die Quantifizierung von Kontaktgefrierraten von atmosphärisch relevanten komplexen Aerosolpartikeln, und erste Wolkenkammerexperimente zum Kontaktgefrieren. Außerdem werden wir die Erstellung und Pflege einer neuen Datenbank für Laborergebnisse zur heterogenen Eisnukleation unterstützen.
Atmospheric CO2 concentrations present a repetitive pattern of gradual decline and rapid increase during the last climate cycles, closely related to temperature and sea level change. During the Last Glacial Maximum (LGM; 23-19 kyr BP), when sea level was ca. 120 m below present, the ocean must have stored additionally about 750 Gt carbon. There is consensus that the Southern Ocean represents a key area governing past and present CO2 change. The latter is not only of high scientific but also of socio-economic and political concern since the Southern Ocean provides the potential for an efficient sink of anthropogenic carbon. However, the sensitivity of this carbon sink to climate-change induced reorganizations in wind patterns, ocean circulation, stratification, sea ice extent and biological production remains under debate. Models were not yet able to reproduce the necessary mechanisms involved, potentially due to a lack of the dynamic representation/resolution of atmospheric and oceanic circulation as well as missing carbon cycling. Data on past Southern Ocean hydrography and productivity are mainly from the Atlantic sector, thus do not adequately document conditions in the Pacific sector. This sector is not only the largest part of the Southern Ocean, but it also represents the main drainage area of the marine-based West Antarctic Ice Sheet (WAIS). In the proposed study we aim to generate paleo-data sets with a newly established proxy method from sediment core transects across the Pacific Southern Ocean. This will enhance the baselines for the understanding and modeling of the Southern Ocean's role in carbon cyling, i.e. ocean/atmosphere CO2 exchange and carbon sequestration. It will also allow insight into the response of the WAIS to past warmer than present conditions. Paired isotope measurements (oxygen, silicon) will be made on purified diatoms and radiolarians to describe glacial/interglacial contrasts in physical and nutrient properties at surface and subsurface water depth. This will be used to test (i) the impact of yet unconsidered dust-borne micronutrient deposition on the glacial South Pacific on shifts of primary productivity, Si-uptake rates and carbon export, (ii) the 'silicic-acid leakage' hypothesis (SALH) and (iii) the formation and extent of surface water stratification. Diatom and radiolarian oxygen isotopes will provide information on the timing of surface ocean salinity anomalies resulting from WAIS melt water. Climate model simulations using a complex coupled atmosphere ocean general circulation model (AOGCM) in combination with a sophisticated ocean biogeochemical model including Si-isotopes will be used for comparison with the paleo records. The analysis will cover spatial as well as temporal variability patterns of Southern Ocean hydrography, nutrient cycling and air-sea CO2-exchange. With the help of the climate model we aim to better separate and statistically analyse the individual impacts of ocean circulation and bio
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.
The decomposition of terrestrial organic material such as leaf litter represents a fundamental ecosystem function in streams that delivers energy for local and downstream food webs. Although agriculture dominates most regions in Europe and fungicides are applied widely, effects of currently used fungicides on the aquatic decomposer community and consequently the leaf decomposition rate are largely unknown. Also potential compensation of such hypothesised adverse effects due to nutrients or higher average water temperatures associated with climate change are not considered. Moreover, climate change is predicted to alter the community of aquatic decomposers and an open question is, whether this alteration impacts the leaf decomposition rate. The current projects follows a tripartite design to answer these research questions. Firstly, a field study in a vine growing region where fungicides are applied in large amounts will be conducted to whether there is a dose-response relationship between the exposure to fungicides and the leaf decomposition rate. Secondly, experiments in artificial streams with field communities will be carried out to assess potential compensatory mechanisms of nutrients and temperature for effects of fungicides. Thirdly, field experiments with communities exhibiting a gradient of taxa sensitive to climate change will be used to investigate potential climate-related effects on the leaf decomposition rate.
Outbreaks of foodborne illness linked to consumptions of fresh, or partially processed, agricultural products are a growing concern in industrialized and developing countries. The incidence of human pathogens on fresh fruits and vegetables is often related to the use of recycled wastewaster in surface irrigation as well as high amounts of animal manure in agricultural management practice. Thereby the soil inhabiting fauna plays an important role in the transport and dissemination of microorganisms. The focus of the proposed project is on nematodes, well known vectors for bacteria and viruses in soil. The major goals are to: (1) survey human pathogens in soil and on/in free-living and plant parasitic nematodes in agriculture field sites irrigated with recycled wastewater or fertilized with fresh animal manure in Israel and the Palestinian Authority, (2) assess the function of nematodes as vectors in transmitting bacteria from microbial hot spots to plants, and (3) localize bacteria on and/or within the nematode and identify bacterial factors required for survival in the nematode host. Understanding the mechanisms involved in dissemination of human pathogens by nematodes will enhance the ability to develop practical means to minimize contamination of fresh produce and increase safety in food production.
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.
Most soils develop distinct soil architecture during pedogenesis and soil organic carbon (SOC) is sequestered within a hierarchical system of mineral-organic associations and aggregates. Permafrost soils store large amounts of carbon due to their permanently frozen subsoil and a lack of oxygen in the active layer, but they lack complex soil structure. With permafrost thaw more oxidative conditions and increasing soil temperature presumably enhance the build-up of more complex units of soil architecture and may counterbalance, at least partly, SOC mineralization. We aim to explore the development of mineral-organic associations and aggregates under different permafrost impact with respect to SOC stabilization. This information will be linked to environmental control factors relevant for SOC turnover at the pedon and stand scale to bridge processes occurring at the aggregate scale to larger spatial dimensions. We will combine in situ spectroscopic techniques with fractionation approaches and identify mechanisms relevant for SOC turnover at different scales by multivariate statistics and variogram analyses. From this we expect a deeper knowledge about soil architecture formation in the transition of permafrost soils to terrestrial soils and a scale-spanning mechanistic understanding of SOC cycling in permafrost regions.
Soil microorganisms can mobilize and immobilize phosphorus (P), and therefore strongly affect the availability of P to plants. In this project we hypothesize that the ratio of labile P to microbial P increases during the transition from acquiring to recycling ecosystems. Microbial and plant P uptake will be studied with 33P that will be quantified in microbial and plant biomass as well as in lipids. To what extent microorganisms immobilize and mobilize P during decomposition of soil organic matter will be explored with a 14C/33P labeled monoester. Seasonal dynamics of actual and potential P mineralization (33P dilution and phosphatase activity), and microbial P immobilization will be studied with soils of the transition from acquiring to recycling ecosystems. The contribution of litter-derived P will be explored in a litter exclusion experiment in the field. Spatial patterns of microbial and plant P mineralization in the rhizosphere will be explored by analyses of areas of high acid and alkaline (=microbial-derived) phosphatase activity by soil zymography, and their relations with areas of high rhizodeposition (14C imaging). In conclusion, we will analyse mechanisms of actual and potential microbial P mineralization and immobilization, localization, and consequences for P uptake by plants.
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