EGU2020-20330
https://doi.org/10.5194/egusphere-egu2020-20330
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Soil texture determines the microbial processing from litter to POM and MAOM in the detritussphere

Kristina Witzgall1, Alix Vidal1, David Schubert2, Carmen Höschen1, Steffen Schweizer1, Franz Bruegger3, Valerie Pouteau4, Hirte Juliane5, Claire Chenu4, and Mueller Carsten W1
Kristina Witzgall et al.
  • 1Lehrstuhl für Bodenkunde, Department ofEcology and Ecosystem Managemen, Center of Life and Food Sciences Weihenstephan, Technische Universität München, Freising-Weihenstephan, Germany
  • 2Technische Universität München, Freising-Weihenstephan, Germany
  • 3Institute of Soil Ecology, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
  • 4UMR Ecosys, AgroTechParis, Batiment EGER, Thiverval Grignon, France
  • 5Plant-Soil Interaction Group, Division Agroecology and Environment, Agroscope, Zurich, Switzerland

Soil texture and microorganisms are key drivers controlling the fate of organic matter (OM) originating from decaying plant litter, and thus the stabilization of soil organic matter (SOM). However, the understanding of the mutual interactions between microbial litter decay and soil structure formation controlled by different soil textures remains incomplete. We monitored the fate of litter-derived OM (using 13C isotopic enrichment) from decaying litter (shredded maize leaves) to microorganisms and SOM in two differently textured soils (sand and loam). The two soils were incubated with litter mixed in the top layer in microcosms for 95 days during which regular CO2 and 13CO2 measurements were conducted. After the incubation, each microcosm was divided in three to separate a top, center and bottom layer. Using a physical soil fractionation scheme, we assessed the fate of litter-derived OM to free and occluded particulate OM (POM), as well as mineral associated OM (MAOM). All SOM fractions were analysed with respect to their mass distribution, C, N, and 13C contents, and for their chemical composition using compound-specific 13C-CPMAS NMR spectroscopy. The effects of contrasting textures on the total microbial community structure were studied using phospholipid fatty acids (PLFA) and the incorporation of litter-derived C into individual PLFAs was assessed via 13C-PLFA. Lastly, scanning electron microscopy and nano scale secondary ion mass spectroscopy (NanoSIMS) analysis of free POM of both textures enabled qualitative insights directly at the biogeochemical interface of the microbial hot spot of decaying plant litter.

We were able to clearly demonstrate higher contents of litter-derived OM still residing as free POM in the loamy textured soil after the 95 day-incubation, while higher contents were found in occluded and MAOM in the sandy textured soil. This indicated that the overall litter decomposition was refrained in the finer-textured soil, whereas microbial alteration and allocation of litter-derived compounds was promoted in the coarser textured soil. This was further corroborated by higher respiration and higher amounts of respired litter-derived CO2-C in the sandy soil. The PLFA analysis showed a coherent pattern between the textures, with similar community structures in all treatments and significant increases in microbial abundance in the top layers induced by litter addition. This increase was found most pronounced in fungal biomarkers, which was in line with the 13C-PLFA measurements revealing over 90% of fungal biomarkers to be of litter-origin (compared to 30-40% in the other microbial groups). The labelled PLFA profiles also confirmed the importance of fungi as a vector for litter-derived OM into deeper layers of the soil columns, with significantly higher litter-derived fungal markers also in center and bottom layers. The NanoSIMS measurements verified the high 13C enrichment in fungal hyphae and further revealed clay minerals embedded in enriched microbial-derived extracellular polymeric substances and intertwined with hyphae directly on top of the POM. Based on this comprehensive data, we highlight that regardless of the texture, plant litter in association with microbial-derived products represent a hot spot for soil structure formation by harbouring a core for aggregation and MAOM formation.

How to cite: Witzgall, K., Vidal, A., Schubert, D., Höschen, C., Schweizer, S., Bruegger, F., Pouteau, V., Juliane, H., Chenu, C., and Carsten W, M.: Soil texture determines the microbial processing from litter to POM and MAOM in the detritussphere, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20330, https://doi.org/10.5194/egusphere-egu2020-20330, 2020

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