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Aktuelle Forschungsprojekte

The role of clay minerals and metal oxides for organic matter
stabilization in highly weathered tropical soils
Leitung:Robert Mikutta (Martin Luther University Halle-Wittenberg), Karlheinz Feger, Karsten Kalbitz, Maximilian Kirsten (Technical University Dresden), Carsten W. Müller (Technical University Munic)
Laufzeit:2017-2019
Förderung:Deutsche Forschungsgemeinschaft – DFG
Effects of land-use change from natural to agricultural ecosystems on storage and stabilization of soil organic matter (SOM) are not well understood in highly weathered acidic tropical soils, although these soils are largely affected by such perturbations. The uncertainty about losses of SOM and the responsible mechanisms have a huge impact because functioning of these tropical soils highly depends on SOM. Therefore, a strong need exists to determine the most important properties and mechanisms responsible for stabilization of SOM in such highly weathered tropical soils. Metal oxides and clay minerals are the most important agents for storage and stabilization of SOM in these soils. However, neither is information available if an optimum ratio of metal oxides to oxide-free clay exists for SOM storage and stabilization, nor if the formation of mineral-organic associations (MOA) and aggregates as key mechanisms have the same optimum. The overall objective of the project is to disentangle the complex interactions between metal oxides and clay minerals on storage and stabilization of SOM in highly weathered acidic soils of humid tropical Africa. We will use a unique gradient in the ratio of metal oxides to clay in the East Usambara Mountains (NE Tanzania) to study the relative importance of the two key stabilization mechanisms - the formation of MOA and physical protection of SOM by occlusion in aggregates. The gradient in metal oxides to clay will be combined with a gradient in land-use from natural forest to cropland. Soil samples will enter a combined density and aggregate size fractionation to differentiate between SOM storage provided by MOAs and aggregates. A basic soil characterization and advanced approaches to characterize soil minerals and their interactions with SOM (e.g., XRD, XRF, XPS, FTIR; SEM, NanoSIMS) will be applied to these fractions. In addition, incubation experiments will be used to determine the impact of metal oxides and clay on SOM stabilization and the responsible mechanisms. This improved quantitative process knowledge will contribute to a better predictive power of land-use change impacts on SOM in these vulnerable tropical soils, thus setting the base for strategies preventing SOM losses for sustainable land use.
Research project “Innovation for sustainable agricultural utilization of resources and climate adaption in arid environments of Kazakhstan and Southwest Siberia” - Subproject 2b: Effects of climate and land use on organic matter dynamics of Kazakh steppe soils
Leitung:Robert Mikutta and Klaus Kaiser (Martin Luther University Halle-Wittenberg) with national partners (Geography at MLU, Helmholtz-Zentrum für Umweltforschung GmbH – UFZ, Leibniz Universität Hannover, Amazonen-Werke H. Dreyer GmbH & Co. KG. Umwelt-Geräte-Technik GmbH) and Kazakh partners.
Laufzeit:2017-2019
Förderung:Bundesministerium für Bildung und Forschung – BMBF
The steppe regions of Kazakhstan belong to the core areas of agricultural production in Central Asia, responsible for about 90% of corn production. The highly intensive agricultural monoculture production in the past decades caused severe soil degradation (desertification, erosion, salinization) today accounting for about 75% of the total area of Kazakhstan. The multidisciplinary project "Innovation for sustainable agricultural utilization of resources and climate adaption in dry regions of Kazakhstan and Southwest Siberia"; "Innovationen für nachhaltige landwirtschaftliche Ressourcennutzung und Klimaanpassung in Trockensteppen Kasachstans und Südwestsibiriens") focuses on the development and implementation of climate-adapted soil management strategies in the semi-arid steppe soils of Kazakhstan and Southwest Siberia. In this subproject we intend to determine the current state of Kazakh soils with respect to soil organic matter stocks under diverse land use regimes in order to set the scientific basis for future development of advanced soil management systems and for predicting the accompanied changes on the C sequestration potential of heavily used steppe soils. Primary objectives of this project are (i) the analysis of soil physicochemical properties depending on climate, land use and management, (ii) quantification of organic matter stocks including organically bound nutrients, (iii) evaluation of organic matter degradation patterns under different temperatures and moisture, and finally (iv) assessment of soil structure changes in dependence of climate and soil management and the consequences for C sequestration and soil water balance.
The leak in the phosphorus cycle ‒ exploring the mechanisms and controls of phosphorus leaching in soils of acquiring and recycling forest ecosystems
Leitung:Klaus Kaiser (Martin-Luther-Universität Halle-Wittenberg), Frank Hagedorn (Eidgenössische Forschungsanstalt für Wald, Schnee und Landschaft; Birmensdorf, Schweiz)
Laufzeit:2017-2019
Förderung:Deutsche Forschungsgemeinschaft – DFG
Schweizer Nationalfond – SNF
During ecosystem development, forest ecosystems gradually change from the acquisition of rock P to the recycling of organic P. Orthophosphate and dissolved organic P (DOP) are released in the organic layers and partly leached into the mineral soil. Our results obtained during phase 1 of SPP 1685 indicate decreasing leaching of orthophosphate from organic layers with increasing recycling tendency of the forest ecosystems. In comparison, DOP does not decrease much. Most DOP is not enzymatic hydrolysable, and consequently bioavailability is little. Orthophosphate decreases with depth in the mineral soil; the decline in DOP is less strong. Likely, DOP contributes substantially to the steady P loss from all forest ecosystems, but also orthophosphate is not retained completely in the mineral soil. Yet, the factors controlling the differential production of dissolved P in organic layers of acquiring and recycling forest ecosystems are not resolved. Also, the causes for the steady leaching of dissolved P are not fully understood. The proposed work aims at exploring the mechanisms and controls of the mobilization and leaching of P in forest ecosystems. Mobilization of P in organic layers will be assessed by measuring the release of P forms and DOP bioavailability in the SPP-fertilization experiment and in microcosms with organic matter of different quality. Also, we will trace the fate of 13C-labelled compounds to determine DOP turnover and the rate limiting steps in the mobilization process. By measuring P leaching with and without nutrient fertilization and from substrates with differing stoichiometry (C:P:N ratios), we can deduce if DOP production is driven by P availability or is rather a byproduct of soil organic matter cycling. In climate chambers, we will estimate the temperature dependency of P mobilization processes, which is a key factor in the P cycle. One possible cause for the mobility of dissolved P is colloidal transport. We, thus, will analyze soil solutions for colloids by ultracentrifugation. Binding to colloids can also explain the poor enzymatic hydrolyzability of DOP. The possible release of DOP from soil matrix-bound organic P compounds will be tested by separating DOP in P-rich and P-poor fractions, combined with 14C analyzes. Characterization of dissolved P will be carried out with 31P-NMR, which is often limited by the small amounts of P in subsoil solutions. Therefore, we will employ XPS with Ag anode excitation to determine P binding forms in small samples. Part of the project will be dedicated to the development of this new method. In order to generalize the obtained results, we will determine dissolved P in soil waters sampled sporadically at a number of additional forest sites. Finally, we will contribute to the synthesis on transport- and flux-related results within SPP 1685, which is a prerequisite for the modeling of the P cycle in forest ecosystems.
Plant-microbe strategies for utilization of mineral-associated P sources
Leitung:Prof. Dr. R. Mikutta, Prof. Dr. B. Glaser, Prof. Dr. G. Guggenberger (Universität Hannover)
Laufzeit:2017-2019
Förderung:Deutsche Forschungsgemeinschaft – DFG
Depleted resources in easy accessible apatite as well as the sorption of inorganic and organic phosphorus (P) to secondary minerals are the main proposed aspects for P limitation of old weathered forest ecosystems. In spite of that indications exist that sorption of P is not irreversible and that life communities are capable to recycle mineral-associated P. But the underlying processes and controlling factors are still poorly known. In this project we will test the hypothesis that particularly in P-limited ecosystems plant-microbe communities can utilize mineral-bound P. We assume that a higher P use efficiency from secondary minerals, especially of sorbed orthophosphate in comparison to P monoesters, is due to an enhanced investment of photosynthates into weathering-active mycorrhiza and bacteria, with such a strategy being realized for both ectomycorrhized plants as well as for plants living in symbiosis with arbuscular fungi. Therefore, mesocosm experiments with soils varying in P supply and amended with additional P sources, i.e. ferrihydrite with adsorbed orthophosphate and P-monoesters, will be run under Fagus sylvatica (ectomycorrhiza) und Acer pseudoplatanus (arbuscular mycorrhiza). 13CO2 isotope labeling and substance-specific 13C analysis in phospholipid fatty acids and low-molecular weight organic acids as well as enzyme activity measurements will inform about the investment of plants into microbial communites as well as weathering agents as a function of soil P availability and P types present. In a field exposure experiment, P adsorption complexes will be buried and incubated for one year to verify the mesocosms results. Phosphorus losses will be assessed by X-ray fluorescence and photoelectron spectroscopy and the involved microbial communities will be described based on quantitative real-time PCR and 454 pyrosequencing. The obtained data will clarify whether the recycling of P from secondary minerals is a relevant process and which strategies of life are realized.
Relevance of functional soil organic matter fractions for kinetics and spatiotemporal patterns of denitrification
Leitung:Prof. Dr. R. Mikutta, Prof. Dr. J. Böttcher (Universität Hannover)
Laufzeit:2016-2018
Förderung:Deutsche Forschungsgemeinschaft – DFG
Denitrification is a key transformations process, which returns nitrogen (N) from soil back into the atmosphere as N2 and N oxides and therefore plays an important role for the closure of the global N cycle. Despite soil organic matter (OM) is known to fuel denitrification by acting as an electron donor, the role of OM quality and its spatial and temporal bioavailability is only poorly understood. Such information is mandatory for understanding and predicting the hot-spot─ and hot-moment─behavior of N trace gas emissions from agricultural soils. The present project is part of the new DFG research unit “Denitrification in Agricultural Soils: Integrated Control and Modelling at Various Scales (DASIM)”, which tackles the challenges of enhancing the mechanistic understanding of soil denitrification and developing new modeling tools for describing the heterogeneity of N gas fluxes from agricultural soils. Our subproject aims to study the effect of OM type and composition on soil denitrification. We will link the properties and abundance of different functional OM fractions (dissolved, particulate, and mineral-associated OM) to the onset and extent of soil denitrification and the respective gas products. Controlled incubation experiments utilizing different organic substrates and soil aggregate size-fractions will be conducted to derive rate equations for denitrification as well as threshold oxygen concentrations and to identify the prime locations of soil denitrification activity. The spatial arrangement of OM in soil will be evaluated microscopically using thin sections of aggregates. Based on OM properties, as judged from element analytics, 13C-NMR and X-ray photoelectron spectroscopy, and denitrification data we will develop an OM-specific quality index for implementation and use in denitrification models.
Forschergruppe 2179: "MAD Soil - Microaggregates: Formation and turnover of the structural building blocks of soils" - Subproject 4: Spatiotemporal interactions of aggregate-forming agents within soil microaggregates: Consequences for aggregate structure and stability
Leitung:Prof. Dr. G. Guggenberger (Universität Hannover), Prof. Dr. R. Mikutta
Laufzeit:2015-2017
Förderung:Deutsche Forschungsgemeinschaft – DFG
The identification of mechanisms in soil microaggregation is only possible by linking the surface chemistry of involved components to the formation and properties of microaggregates. We aim at identifying the role of different aggregate-forming agents (organic matter, clay minerals, metal oxides) involved in microaggregate formation and stability. For this, we will investigate the formation and temporal and spatial change of physicochemical properties of microaggregates (20-250 μm) and their building units (<20 μm) in a series of batch and microcosm experiments as well as in a soil toposequence. Our basic analytical approach relies on X-ray photoelectron spectroscopy (XPS) of microaggregates to determine the elemental composition of inorganic and organic surfaces. The microaggregate surface chemistry (XPS), morphology (scanning electron microscopy), particle and pore size distribution (laser diffraction, Hg porosimetry, gas adsorption), as well as wettability (contact angle analysis) will be related to the stability of microaggregates. Consequences of changing environmental conditions to microaggregate stability will be assessed upon selective removal of aggregate-forming agents via microbial reduction of FeIII oxides, organic matter mineralization, and pH shifts. These studies will provide a mechanistic background for modeling microaggregation with relevant implications for soil organic matter stabilization.
When nano-scale meets biodiversity: retention and recycling mechanisms of organic phosphorus in soil (SPP 1685 "Ecosystem Nutrition: Forest Strategies for limited Phosphorus Resources")
Leitung:Prof. Dr. R. Mikutta, Dr. J. Boy (Universität Hannover), Prof. Dr. G. Guggenberger (Universität Hannover)
Laufzeit:2013-2016
Förderung:Deutsche Forschungsgemeinschaft – DFG
Soil organic matter is considered to become an increasingly important source of bioavailable phosphorus (P) with depletion of inorganic P within primary minerals. Current concepts on P cycling and mobilization of organic P largely ignore the formation of mineral-organic associations. This project aims to link processes occurring at the nanoscale on mineral surfaces with the bioavailability of organic P, with particular focus on the influence of biodiversity and establishment of functional niches by microbial communities on P recycling in soils. Along a soil P availability gradient the proportion of mineral-associated P as well as its composition (31P NMR and X-ray absorption near edge structure spectroscopy) will be determined and related to mineralogical soil properties. Based on adsorption and desorption experiments using both, monomeric and polymeric P sources, the recycling potential of mineral-bound organic P by various biotic communities (plants, mycorrhiza, bacteria) will be determined in mesocosm and field experiments. We expect to assess the relevance of mineral-associated organic P for the P recycling of forest ecosystems and to identify the major controlling abiotic and biotic variables.
Phototrophic community succession as driver of mineral weathering and soil formation along chronosequences in maritime Antarctica (SPP 1158 "Antarctic Research")
Leitung:Dr. J. Boy, Prof. Dr. R. Mikutta, Dr. O. Shibistova, Prof. Dr. G. Guggenberger, Prof. Dr. R. Godoy
Laufzeit:2013-2016
Förderung:Deutsche Forschungsgemeinschaft – DFG
Weathering is of utmost importance for the support of life on earth, as it turns bedrock into soil and delivers nutrients to organisms. Vice versa, life itself is heavily engaged in mineral weathering by investment of photosynthates into weathering processes. We aim at investigating the processes and thresholds in biogenic weathering as a function of photoautotrophic community succession from microalgae/cyanobacteria to lichen-dominated stages towards the appearance of higher plants along soil chronosequences built by global-change induced glacier retreat in maritime Antarctica. For this, along the chronosequences weathering agents, organic carbon allocation to the soil, mineral in-situ composition and biogenic weathering on surfaces of introduced and defined, rock forming minerals will be assessed and related to phototrophic community structure. We expect to contribute to the understanding if and how life alters its own habitat in an extreme terrestrial ecosystem, and how this biogeosystem may respond to changes induced by Global Change in an increasingly warmer Antarctica.
Global comparison of the biogenic weathering rates of mycorrhiza
Leitung:Dr. J. Boy, Prof. Dr. R. Mikutta, Prof. G. Guggenberger
Laufzeit:2013-2016
Förderung:Deutsche Forschungsgemeinschaft – DFG
Weathering is of utmost importance for the support of life on earth, as it delivers nutrients to organisms. Besides physico-chemical weathering, biogenic weathering might contribute substantially to overall mineral degradation and supply of nutrients to the ecosystem. Mycorrhizal fungi are increasingly identified to be a major player in biogenic weathering, but the underlying processes are still little understood as comparative in situ studies on large scale are lacking. This project aims at elucidating the biogenic weathering functioning of mycorrhizal fungi in a global field study by comparing forest ecosystems dominated by closely related plants either realizing arbuscular mycorrhiza (AM) or ectomycorrhiza (EM). Mesh bags containing minerals with different stability and nutrient contents are buried at 21 biogeochemically monitored sites for up to three years. Using multiple wet chemical, imaging, and spectroscopic methods we will assess (i) the extent of fungal colonization and type of mycorrhiza involved in mineral weathering, (ii) the selectivity, magnitude and rate of mycorrhiza-induced mineral weathering depending on ecosystem properties, and (iii) the contribution of different organism groups to biogenic weathering. This unique data set will largely extend our current understanding of the role of biota in ecosystem functioning and sustainability on global scale.
Forschergruppe 1806: "SubSOM - The forgotten part of carbon cycling: Organic matter storage and turnover" - Subproject 5: Origin and fate of dissolved organic matter in the subsoil
Leitung:Prof. Dr. G. Guggenberger (Universität Hannover), Prof. Dr. R. Mikutta, Prof. Dr. K. Kalbitz (TU Dresden)
Laufzeit:2013-2016
Förderung:Deutsche Forschungsgemeinschaft – DFG
Details:
SPICE III Indonesia: TIMES – Terrestrial Influences on Mangrove Ecology and Sustainability of their resources - Carbon sequestration as a function of land use change in mangroves
Leitung:Dr. J. Boy, Prof. Dr. R. Mikutta, Prof. Dr. G. Guggenberger
Laufzeit:2012-2016
Förderung:Deutsche Forschungsgemeinschaft – DFG
This project aims at understanding the processes of carbon (C) sequestration in representative mangrove ecosystems in Indonesia (Segara Anakan Lagoon, Java, Togian Islands, Sulawesi, Berau, Kalimantan) as a function of mangrove conversion, in order to develop and test an easy-to-use tool for pricing of C related environmental services (CRES) in REDD and PES schemes. We will investigate into the C sequestration potential of mangrove by linking C stocks to sources, composition, and turnover of organic matter (OM) species in soil. Furthermore, we aim to clarify to which extent these functions are triggered by plant and microorganisms (bacteria and fungi) species composition in pristine and used (including completely deforested) mangroves. This process-based understanding of utilization thresholds is a prerequisite for successful future management scenarios dealing with C sequestration in mangrove ecosystems. Moreover, it will be tested whether identification of aboveground species composition could act as a valid indicator for CRES, both in economically based decision making on broader scale and local cost-efficient monitoring of the consecutive provision of CRES.
KULUNDA: Ökologische und Ökonomische Strategien zur nachhaltigen Landnutzung in Russischen Steppen: Ein Beitrag zur Anpassung an den Klimawandel - Teilprojekt: Landnutzungseffekte für die Kohlenstoffsequestrierung in Steppenböden
Leitung:Prof. Dr. G. Guggenberger, Prof. Dr. R. Mikutta, Dr. O. Shibistova
Laufzeit:2012-2016
Förderung:Bundesministerium durch Bildung und Forschung (BMBF)
Die Böden der Kulunda-Steppe in Süd-Sibirien leiden aufgrund unsachgemäßer Bodenbewirtschaftung und Erosion an substantiellen Verlusten an organischem Kohlenstoff (C). Zielstellung des Teilprojektes ist es daher, die wissenschaftlichen Grundlagen für ein C-optimiertes nachhaltiges Bodenmanagement in diesem intensiv genutzten Agroökosystem zu legen. Das Teilprojekt widmet sich der Analyse des C-Speicherpotentials der Böden unter verschiedenen Landnutzungs- und Bodenbearbeitungsformen entlang von Zeitserien und Klimagradienten. Im Rahmen der an der Leibniz Universität Hannover vorgesehenen Arbeiten umfass dieses sowohl die chemische und funktionelle Charakterisierung von organischer Bodensubstanz als auch die Erfassung ihres Umsatzes. Aus den Ergebnissen sollen Richtlinien für C-optimierte Landnutzung-/Bodenbearbeitungsverfahren erarbeitet werden. Spezifische Arbeitsziele sind: (1) Quantifizierung der C-Vorräte und Analyse der Qualität organischer Bodensubstanz in Steppenböden unterschiedlicher landwirtschaftlicher Nutzung (Brache, konventionelle bzw. pfluglose Bodenbearbeitung), (2) Analyse des C-Umsatzes ausgewählter Fraktionen organischer Substanz mittels 14C-Datierung, (3) Abschätzung des Einflusses veränderter Umweltbedingungen (Climate Change) auf C-Vorräte und C-Umsatz durch Analysen entlang von Klimagradienten innerhalb der Kulunda-Steppe, sowie (4) Datenanalyse und Entwicklung eines Entscheidungsmediums (Modell) für die Anwendung von C-freundlichen, nachhaltigen Landnutzungs- und Bodenbearbeitungsverfahren.
NTH Graduate School GeoFluxes - Microbially-mediated transformation and mobilization of Fe-organic associations in the critical zone
Leitung:Prof. Dr. G. Guggenberger, Prof. Dr. R. Mikutta, Prof. Dr. A. Schippers
Laufzeit:2012-2015
Förderung:Deutsche Forschungsgemeinschaft – DFG
Ferric hydrous oxides (FHO) are ubiquitous in soils and sediments. Their geochemical behavior has a profound influence on the biogeochemical cycling of many elements including iron, carbon, phosphorus, sulfur, nitrogen, as well as trace metals. While it is well accepted that FHO are significantly involved in the storage of organic matter (OM) in aerated soils worldwide, under oxygen-deficient conditions Fe-OM phases are prone to microbial-mediated dissolution, thus counteracting the proposed stabilizing effect on associated compounds. Adsorbed or coprecipitated OM is believed to affect the rate of Fe reduction and solution transfer by its ability to shuttle electrons from the involved bacteria to the Fe solid or by the blocking of reactive Fe centers. The focus of this project is therefore to study the effect of the amount and composition of Fe-bound OM on the dissimilatory Fe(III) reduction and properties of a range of pedogenic Fe oxides under varying environmental conditions, as well as on the concomitant mobilization of co-associated compounds (dissolved OM; DOC, trace elements). The results of these batch studies will be transferred to field conditions by relating the Fe-cycling microbial communities to the abundance and properties of FHO phases present along geochemical soil gradients.
Changes in the mineral composition of paddy soils upon redox cycles
Leitung:Prof. Dr.-Ing. R. Jahn, Dr. K. Kaiser, Prof. Dr. S. Fiedler (Universität Mainz), Prof. Dr. K. Kalbitz (TU Dresden)
Bearbeiter:Pauline Winkler
Laufzeit:2012-2016
Förderung:Deutsche Forschungsgemeinschaft – DFG (Projekt JA 523/16-1); Teilprojekt DFG-Forschergruppe 995 „Biogeochemistry of paddy soil evolution”
Previous studies indicated that the development and biogeochemistry of paddy soils relates to the parent material, thus the original soil paddies derive from. The proposed research focuses on redox-mediated changes in mineral composition and mineral-associated organic matter (OM) during paddy transformation of different soils. We plan to subject soil samples to a series of redox cycles, in order to mimic paddy soil formation and development. Soils with strongly different properties and mineral composition as well as at different states of paddy transformation; ranging from unchanged soils to fully developed paddy soils, are to be included. We hypothesize that dissolved organic matter is one key driver in redox-mediated transformations, serving as an electron donator as well as interacting with dissolved metals and minerals. The extent of effects shall depend on the parent soil’s original mineral assemblage and organic matter and their mutual interactions. The experimental paddy soil transformation will tracked by analyses of soil solutions, of the (re-)distribution of carbon (by addition of 13C-labelled rice straw), of indicative biomolecules (sugars, amino sugars, fatty acids, lignin) and of minerals (including the redox state of Fe). For analyses of organic matter as well as of mineral characteristics we plan to utilize XPS, for Fe-bearing minerals also Mößbauer spectroscopy. This approach of experimental pedology seems appropriate to give insight into the major factors during paddy soil formation and development.
Land-use intensity and Ecological Engineering – Assessment Tools for risks and Opportunities in irrigated rice based production systems (LEGATO)
Leitung:Dr. J. Settele ( UFZ Halle/Saale)
Bearbeiter:Dr. T. Klotzbücher
Laufzeit:2011-2016
Förderung:Bundesmisministerium für Bildung und Forschung (BMBF)
Details:
Forschergruppe 1806: "SubSOM - The forgotten part of carbon cycling: Organic matter storage and turnover"
Leitung:Prof. Dr. B. Marschner, Prof. Dr. J. Bachmann, Prof. Dr. B. Ludwig, PD Dr. E. Priesack
Bearbeiter:Dr. T. Klotzbücher
Laufzeit:2013-2016
Förderung:Deutsche Forschungsgemeinschaft – DFG
Details:

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