Mutual interactions between decaying plant litter, soil microorganisms and mineral particles, controlled by soil texture

Ms Kristina Witzgall1, Ms Alix Vidal1, Mr Steffen Schweizer1, Ms Valerie  Pouteau2, Ms Claire Chenu2, Mr David Schubert3, Ms Juliane Hirte4, Mr Carsten Müller1

1TU München, Lehrstuhl für Bodenkunde, Technische Universität München, Freising-Weihenstephan, Germany, 2UMR Ecosys, AgroTechParis, Batiment EGER, Thiverval Grignon, France, 3TU München, Freising-Weihenstephan, Germany, 4Plant-Soil Interaction Group, Division Agroecology and Environment, Agroscope, Zurich, Switzerland

Soil texture and microorganisms are key drivers controlling the fate of organic matter (OM) from decaying plant litter and thus soil organic matter (SOM) stabilization. A better understanding of mutual interactions between microbial litter decay and soil structure formation controlled by different soil texture remains challenging. We monitored the fate of litter-derived compounds (using 13C isotopic enrichment) from decaying litter (maize leaves) to microorganisms and soil in two differently textured soils (sand and loam). We incubated the two soils with litter mixed in the top layer in microcosms for three months with regular CO2 and 13CO2 measurements. Using a physical soil fractionation scheme, we assessed the fate of the litter-derived OM as free and occluded particulate organic matter (POM) as well as mineral associated OM (MOM) together with the effects of the different textures on the microbial communities using PLFA. The POM and MOM fractions were analyzed with respect to mass distribution, C, N and 13C contents, as well as the chemical composition using 13C-CPMAS NMR spectroscopy. We could clearly demonstrate higher contents of OM in the mineral associated fractions of the sandy textured soil in contrast to the loamy textured soil, where instead higher OM contents were detected in the POM fractions. Thus we show a distinct negative effect of the clay content on MOM, while clay sustains a high level of OM stored as POM. The 13C measurements showed higher enrichment in almost all fractions in the sandy textured soil compared to the loamy soil. The PLFA analysis revealed a coherent pattern between the textures, where microbial activity increased in the top layers and the community structure remained similar in both treatments. This interdisciplinary approach, where biogeochemical and microbiological methods were combined, gave insights in the interactions between decaying plant litter, microorganisms, and soil minerals.


Biography:

Kristina Witzgall, born 1992 in Lund, Sweden.

  • 2016-2019 M.Sc. Sustainable Resource Management, Technical University of Munich, Germany
  • 2018 Internship, Bavarian State Research Centre for Agriculture, Germany
  • 2017-2018 Student Research Assistant, Technical University of Munich, Germany
  • 2016-2017 Student Representative, Technical University of Munich, Germany
  • 2011-2015 B.Sc. Environmental Sciences, Lund University, Sweden

SOIL ORGANIC MATTER

7th International Symposium
Soil Organic Matter

6 – 11 October 2019

Hilton Adelaide

Adelaide, South Australia

Australia

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