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In soils and sediments there is a strong coupling between local biogeochemical processes and the distribution of water, electron acceptors, acids, nutrients and pollutants. Both sides are closely related and affect each other from small scale to larger scale. Soil structures such as aggregates, roots, layers, macropores and wettability differences occurring in natural soils enhance the patchiness of these distributions. At the same time the spatial distribution and temporal dynamics of these important parameters is difficult to access. By applying non-destructive measurements it is possible to overcome these limitations. Our non-invasive fluorescence imaging technique can directly quantity distribution and changes of oxygen and pH. Similarly, the water content distribution can be visualized in situ also by optical imaging, but more precisely by neutron radiography. By applying a combined approach we will clarify the formation and architecture of interfaces induces by oxygen consumption, pH changes and water distribution. We will map and model the effects of microbial and plant root respiration for restricted oxygen supply due to locally high water saturation, in natural as well as artificial soils. Further aspects will be biologically induced pH changes, influence on fate of chemicals, and oxygen delivery from trapped gas phase.
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.
Die Koordinationsstelle Waermeschutzforschung im Hochbau (KWH) will Forschung, auf dem Gebiet des Waermeschutzes, mit dem Forschungsplan koordinieren. Sie will zwischen den einzelnen Forschern vermitteln, sowie mithelfen, Forschungsresultate in die Architektur und Bautechnik einfliessen zu lassen. Im allgemeinen beschraenkt sich die KWH auf die Gebiete der Waermeschutzmassnahmen an der Gebaeudehuelle und auf die passive Sonnenenergie-Architektur. Diese Koordination ist zugleich Ziel und Mittel in der Erfuellung der Aufgaben der KWH. Als wichtige Aufgabe betrachten wir die Beratung des NEFF beim Beurteilen eingehender Gesuche um Forschungsbeitraege. Um diese Beratung nachvollziehbar zu gestalten, haben wir einen Entwurf fuer einen Forschungsplan aufgestellt, mit einer daraus abgeleiteten Kriterienliste. Diese Arbeit erlaubt uns auch, unsere eigenen Forschungsschwerpunkte zu praezisieren, wie z.B. die Installation des Rechenprogrammes DEROB und die damit durchgefuehrten Parameter-Analysen eines Wintergarten. Der Aufbau einer umfassenden Bibliothek ueber Waermeschutz und passive Sonnenenergie-Architektur ist ein weiteres Ziel der KWH. Zusaetzlich ist die KWH jetzt auch an der Koordination des IEA Programms 'Solar', Task 8 beteiligt.
This subproject aims at the development of spectral electrical impedance tomography (EIT) as a non-destructive tool for the imaging, characterization and monitoring of root structure and function in the subsoil at the field scale. The approach takes advantage of the capacitive properties of the soil-root interface associated with induced electrical polarization processes at the root membrane. These give rise to a characteristic electrical signature (impedance spectrum), which is measurable in an imaging framework using EIT. In the first project phase, the methodology is developed by means of controlled rhizotron experiments in the laboratory. The goal is to establish quantitative relationships between characteristics of the measured impedance spectra and parameters describing root system morphology, root growth and activity in dependence on root type, soil type and structure (with/without biopores), as well as ambient conditions. Parallel to this work, sophisticated EIT inversion algorithms, which take the natural characteristics of root system architecture into account when solving the inherent inverse problem, will be developed and tested in numerical experiments. Thus the project will provide an understanding of electrical impedance spectra in terms of root structure and function, as well as specifically adapted EIT inversion algorithms for the imaging and monitoring of root dynamics. The method will be applied at the field scale (central field trial in Klein-Altendorf), where non-destructive tools for the imaging and monitoring of subsoil root dynamics are strongly desired, but at present still lacking.