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Project 3 (phase II):

Microbial Engineers - Drivers of Earth Surface Development and Stabilization

 

Investigator Names and Contact Info:

  • Dirk Wagner (Microbiology). German Research Centre for GeoSciences (GFZ) Potsdam, Germany
  • Thomas Scholten (Soil Science/Geomorphology). University of Tübingen, Germany
  • Peter Kühn (Soil Science/Geomorphology). University of Tübingen, Germany
  • Carsten W. Mueller (Soil Science). University of Copenhagen, Denmark
  • Steffen Seitz (Soil Science/Geomorphology). University of Tübingen, Germany
  • Karsten Schmidt (Soil Science/Geomorphology). University of Tübingen, Germany

 

Chilean Collaborators Involved:

  • Rómulo Oses (Microbial Ecology / Environmental Microbiology). Center of Advanced Studies in Arid Zones (CEAZA) & CRIDESAT - University of Atacama, Chile
  • Oscar Seguel (Soil Sciences). Department of Engineering and Soil Science, Faculty of Agronomy, University of Chile,  Santiago, Chile

 

PhD:

Soil structure formation and organic matter cycling driven by microorganisms, biocrusts and vegetation.

supervisor: Carsten W. Mueller

PhD:

Soil formation and soil erosion driven by microorganisms, biocrusts and vegetation.

supervisor: Thomas Scholten, co-supervisor: Dr. Peter Kühn

 

PhD:

Microbial-driven soil formation under difefrent environmental conditions.

supervisor: Dirk Wagner, co-supervisor: Romulo Oses

 

MSc:

Soil structure formation driven by vascular plants along a climate gradient.

  • Baptist Köppendörfer. Technische Universität München (TUM), Germany

supervisor: Carsten W. Mueller

MSc:

Soil structure formation driven by biocrusts and vascular plants.

  • Franziska Steiner. Technische Universität München (TUM), Germany

supervisor: Carsten W. Mueller

BSc:

Influence of biological soil crustson soil erosion and infiltration processes.

  • Antonia Tertelmann. Universität Tübingen, Germany

supervisor: Thomas Scholten, co-supervisor: Steffen Seitz

 

 

 

Project summary:

Most of Earth is covered by soils and sediments. In this upper layer processes of decomposition of organic matter and structure formation are mediated by microorganisms. In this context, we ask how and to which extend microorganisms control the stabilization and formation of Earth’s surface. We hypothesize that the mechanisms of stabilization by microorganisms occur under all climate conditions but with varying intensity and different microbiological community structure in the presence of different types of vegetation providing energy to the microorganisms. Further, we assume that initial pedogenesis following soil erosion, i.e. structure formation differs in intensity and microbial community structure between erosional and depositional sites and that related process intensities are controlled by climate. Our results from phase show, that non-linear relationships of pedogenic and microbial processes in soils depending on climate with a sharp threshold between arid and semi-arid conditions. Such undulated trends indicate chemical threshold processes and buffer mechanisms in soils. We further found that the soils on the transition between arid and semi-arid conditions are especially sensitive and may be well used as indicators of long and medium-term climate changes. Also soil erodibility behaved in a complex adaptive manner and is not controlled by a fixed set of factors, but by those who show a minimum concentration that is needed to control the erosion process. The hyper-arid, salt-rich northern site has significantly different soil properties in contrast to the three other sites. Further, we were able to demonstrate a clear climatic gradient from north to south with respect to the distribution and composition of differently stabilized soil organic matter fractions in relation to soil aggregation. Using 13C-CPMAS-NMR spectroscopy we demonstrate a clear aggregation driven differentiation in the composition of the SOM fractions, with mostly fresh and labile free particulate and degraded aromatic occluded POM.

In phase 2 we follow the same road of combining microbial and soil formation processes. We ask how and to which extend microorganisms engineer the Earth’s surface development and stabilization. It is well known that they initially fix carbon and nitrogen and that their residues and extracellular substances aggregate primary soil particles. However, it is largely unclear to what extent microorganisms have a qualitative and quantitative influence on the development of initial soils towards developed soils and how this is linked to soil erosion and surface structure stabilization. Following this question, we assume that a large number of functional groups of microorganisms already exist alongside each other at the beginning of soil formation, whereas a dominant structure of individual groups only emerges during further soil development. In arid areas biocrusts are, in addition to microorganisms, essential elements of habitat development and stabilization of the soil surface. Biocrusts for instance provide very effective protection against erosive rainfall. Under humid climate conditions, plants and their extensive root system form a third central element of soil formation and stabilization, because plants interact with their root system as well as biocrusts very closely with microorganisms.

The climate gradient along the Chilean coastal cordillera offers a unique opportunity to analyze the combined effects of microorganisms, biocrusts and plants on soil formation and stabilization. In the second funding phase, we will use three combined simulation experiments to investigate how microorganisms alone and together with biocrusts and plants form and stabilize the earth's surface in initial and further developed soils. This work will reach from disturbed soil samples up to whole intact soil cores which we will study with respect to their microbiological community structures, soil structure development, organic matter allocation between biota and soil. We thus analyse the combined effect of microorganisms, biocrusts and plant roots for stabilizing the earth's surface by means of rainfall simulation using samples from field and lab experiments. In addition to modern microbiological and soil science methods as well as techniques from soil erosion research, the proposed project combines high-resolution imaging and isotope chemical methods from micromorphology and soil science (ESEM-EDX, NanoSIMS). This serves to identify and understand the mechanisms of soil development and stabilization by microorganisms in interaction with soil crusts and plant roots.