Nutrient availability drives carbon storage in particulate vs. mineral-associated organic matter in Antarctic soils

MSc. Luís  Almeida2, MSc. Isabel Prater1, MSc. Luis Colocho Hutarte1, Prof. Andreas Richter3, A/Prof. Carsten W. Mueller1

1Chair of Soil Science, Technical University of Munich, Freising, Germany, 2Department of Soil Science, Universidade Federal de Viçosa,  Viçosa, Brazil, 3Department of Microbiology and Ecosystem Science, University of Vienna, Vienna, Austria

Although low in total carbon, Antarctica with its pristine soils offers unique model systems to study soil organic matter cycling unbiased by high carbon inputs of vascular plants or anthropogenic disturbance. Furthermore, seabird rookeries with locally restricted high inputs of marine derived bioavailable C, N and P create natural gradients affecting vegetation distribution and productivity. Deception Island situated at the Antarctic Peninsula offers a unique setting with very young soils due to volcanic eruptions between 1968 and 70. This allows to study soil organic matter accrual, distribution and composition in newly developing soils in relation to soil nutrient availability. To this end we sampled three spatially separated sites on Deception Island distributed along a transect from higher to lower marine nutrient inputs, respectively. At the sampling sites patches below living and dead moss were sampled, to account for possible future effects on plant coverage by a changing climate. Besides bulk soil C, N, pH and EC analysis, we fractionated the top soils according to density and particle size, analysed the C and N contents of all fractions and the POM and clay fraction by 13C-CPMAS-NMR spectroscopy. Beside the clear local effect of the input of C, N and P by seabirds, we were able to also demonstrate distinct effects of dead moss cover on soil organic matter stocks, in which the dying of vegetation promotes increased soil C contents in sites with high primary productivity. Our results evidence that different nutrient availability lead to a clear shift in the dominating C pools from mineral-associated to particulate organic matter. The chemical composition of the input material is not reflected by mineral-associated organic matter in the clay fractions, indicating the microbial transformation prior to association with mineral surfaces.


Biography:

Carsten W. Mueller is currently an Associate Professor at the Technical University of Munich. Following his graduation in Forest science at the Technical University of Dresden, he did his PhD at the Technical University of Munich. After a PostDoc at Pennsylvania State University he became an Assistant Professor at the Technical University of Munich. He is mainly working on the fate of soil organic matter, from the plant input in rhizosphere and detritusphere over microbial transformations to particulate organic matter and mineral-associated organic matter in the soil. Having worked on soils from all continents, currently he especially focuses on soil structure formation and organic matter allocation in the rhizosphere and pristine environments in the Arctic and in Antarctica. In his research he combines quantitative approaches (e.g. density fractionation, elemental and isotopic analyses, lab incubations) with state of the art chemical (GC-MS, NMR spectroscopy) and spectromicroscopic (SEM, NanoSIMS) techniques.

SOIL ORGANIC MATTER

7th International Symposium
Soil Organic Matter

6 – 11 October 2019

Hilton Adelaide

Adelaide, South Australia

Australia

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