Mikrobiell beeinflusste Bodenbildung in der maritimen Antarktis unter simulierten Umweltbedingungen
Zusammenfassung der Projektergebnisse
Antarctica offers the extraordinary opportunity to study the diversity and function of microbial communities in soil ecosystems and their interrelationship with soil formation in a pristine natural laboratory, even without the influence of higher plants or burrowing animals. Soil formation is traditionally viewed as a sequential chain of processes beginning with physicochemical weathering and aggregate formation. These pedogenic abiotic processes are based on water- and temperature-controlled mechanisms such as wet-dry and freeze-thaw cycles and provide the habitat for microorganisms and pioneer plants. Advances in high-throughput genotyping technology have markedly improved our understanding of the role of microorganisms for the biochemical transformation of soils and sediments in close interrelation with environmental forces. The main goal of the proposed project is to better understand the impact of microbial community structure and function on the pedogenesis of permafrostaffected soils, particularly under changing environmental conditions. For this, we conducted fieldwork on James Ross Island and we conducted an environmental simulation experiment (EnviSimEx) with different environmental conditions of temperature and soil moisture. We used substrates from James Ross Island and organic matter from Usnea antarctica. The two investigates sites on James Ross Island (JRI) can be considered as archetypal sites for coastal and for inland soils. Despite similarities in topographic position and substrates, both soils have distinct differences in chemistry (content of salts indicated by EC, opposing trends in pH and states of weathering, indicated by weathering indices and pedogenic oxides) and microbiology (depth functions of microbial abundances and diversity, e.g. Proteobacteria, Gemmatimonadetes and Thaumarchaeota abundances). The EC values of the soils and the depth function of the pH values clearly showed different conditions for soil formation at the two sites caused by the more exposed coastal location towards the mainly southwesterly winds, resulting in a more intense weathering and higher input of salt by sea spray. Taking weathering and aggregation as indicators of soil formation, we conclude that coastal conditions – in contrast to inland conditions – favor the formation of soils in maritime Antarctica. The EnviSimEx showed that two distinct microbial community clusters can be attributed to the two different substrates from the two profiles on JRI. Whereas substrates exposed to treatments with no organic matter addition did not differ much from the initial state, substrates exposed to treatments with additional organic matter changed substantially on a community level. Although the EnviSimEx has not yet been fully evaluated, it is already apparent that the microbial communities are very flexible and can maintain their function for the development of initial soils as a community. The pending analyses, to what extent organic matter and microbial communities play a role for structure formation will be part of the last publications by the PhD students. This was not originally planned, but to obtain additional information on the role of microbial communities and their functions in the initial soil formation processes under extreme climate conditions, we analysed soil samples from four soil profiles with no to 100% vegetation cover in the foreland of Ecology Glacier on King Georges Island, taken during an expedition in 2014. Here, the main soil forming processes on a decadal times scale are acidification and accumulation of soil organic carbon and nitrogen, accompanied by changes in microbial abundances, microbial community compositions, and plant coverage, whereas quantifiable silicate weathering and the formation of pedogenic oxides occur on a centennial to a millennial timescale after deglaciation. However, the lowering of the soil pH in bare soil can be explained by more active Chitinophagaceae and other potential heterotrophs, and the decomposition of organic material of microbial origin, such as chitin from fungi. In general, Antarctica9s cold climate slows microbial weathering processes and soil formation rates on recently exposed sediments. At sites with no bird or penguin rookeries, coastal environmental conditions favour soil formation in contrast to inland conditions. In summary, we conclude that prokaryotic microorganisms initiate measurable changes of soil properties such as pH at a very early stage (within decades), and thereby promote weathering processes and microstructure formation. Consequently, we hypothesize that pedogenesis and the formation of the native earth surface processes in ice-free areas of Antarctica are driven by microbial succession in microhabitats triggering the gradual alteration of physicochemical properties of sediments and soils.
Projektbezogene Publikationen (Auswahl)
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Active layer monitoring at CALM-S site near J.G.Mendel Station, James Ross Island, eastern Antarctic Peninsula. Science of The Total Environment, 601-602(c(2017, 12)), 987-997.
Hrbáček, Filip; Kňažková, Michaela; Nývlt, Daniel; Láska, Kamil; Mueller, Carsten W. & Ondruch, Jakub
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Alteration of rocks by endolithic organisms is one of the pathways for the beginning of soils on Earth. Scientific Reports, 8(1).
Mergelov, Nikita; Mueller, Carsten W.; Prater, Isabel; Shorkunov, Ilya; Dolgikh, Andrey; Zazovskaya, Elya; Shishkov, Vasily; Krupskaya, Victoria; Abrosimov, Konstantin; Cherkinsky, Alexander & Goryachkin, Sergey
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Pedogenic and microbial interrelation in initial soils under semiarid climate on James Ross Island, Antarctic Peninsula region. Biogeosciences, 16(12), 2481-2499.
Meier, Lars A.; Krauze, Patryk; Prater, Isabel; Horn, Fabian; Schaefer, Carlos E. G. R.; Scholten, Thomas; Wagner, Dirk; Mueller, Carsten W. & Kühn, Peter
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Site conditions and vegetation determine phosphorus and sulfur speciation in soils of Antarctica. Geochimica et Cosmochimica Acta, 246(c(2019, 2)), 339-362.
Prietzel, Jörg; Prater, Isabel; Colocho Hurtarte, Luis Carlos; Hrbáček, Filip; Klysubun, Wantana & Mueller, Carsten W.
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How vegetation patches drive soil development and organic matter formation on polar islands. Geoderma Regional, 27(c(2021, 12)), e00429.
Prater, Isabel; Hrbáček, Filip; Braun, Christina; Vidal, Alix; Meier, Lars Arne; Nývlt, Daniel & Mueller, Carsten W.
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Influence of prokaryotic microorganisms on initial soil formation along a glacier forefield on King George Island, maritime Antarctica. Scientific Reports, 11(1).
Krauze, Patryk; Wagner, Dirk; Yang, Sizhong; Spinola, Diogo & Kühn, Peter
