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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2020-48
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2020-48
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 25 Feb 2020

Submitted as: research article | 25 Feb 2020

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This preprint is currently under review for the journal BG.

Bacterial and fungal predator – prey interactions modulate soil aggregation

Amandine Erktan1, Matthias C. Rillig2, Andrea Carminati3, Alexandre Jousset4, and Stefan Scheu1 Amandine Erktan et al.
  • 1J.F. Blumenbach Institute of Zoology and Anthropology, University of Goettingen, 37077 Goettingen, Germany
  • 2Institut für Biologie, Freie Universität Berlin, 14195 Berlin, Germany
  • 3Chair of Soil Physics, University of Bayreuth, 95440 Bayreuth, Germany
  • 4Institute of Environmental Biology, Ecology and Biodiversity, Utrecht University, 3584CH Utrecht, the Netherlands

Abstract. The formation and stabilisation of soil macro-aggregates protects soils from erosion, a major worldwide threat on soils. While the role of bacteria and fungi in soil aggregation is well established, how predators feeding on microbes modify soil aggregation has hardly been tested. Here, we studied how predators modulate the effect of microbial prey on soil aggregation. We focused on two predator – prey interactions: bacterial-based interactions comprising amoebae (Acanthamoeba castellanii) grazing on free-living bacteria (Pseudomonas fluorescens), and fungal-based interactions comprising collembolans (Heteromurus nitidus) grazing on saprotrophic fungi (Chaetomium globosum). We conducted a microcosm experiment lasting six weeks and assessed changes in soil aggregate formation and stabilisation, together with modifications in soil microbial communities (PLFAs). We further traced the food resource consumed by microbes using δ13C isotopic tracing. The protist A. castellanii increased the formation of soil aggregates but decreased their stability, without affecting bacterial abundance and community composition, suggesting that the changes were due to amoebae-mediated changes in the production of bacterial mucilage. Saprotrophic fungi showed the highest positive effect on soil aggregate formation and stabilisation, associated with a more efficient use of particulate organic carbon (chopped litter) added to the microcosms. Adding collembolans decreased the abundance of fungi and their ability to capture carbon of litter origin, with negative consequences on soil aggregation. Our work here has demonstrated that trophic interactions are important for achieving a mechanistic understanding of biological contributions to soil aggregation.

Amandine Erktan et al.

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Amandine Erktan et al.

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Short summary
Soil aggregation is crucial for protecting soils from erosion, a major worldwide threat. While the role of bacteria and fungi in soil aggregation is well established, how predators feeding on microbes modify soil aggregation has hardly been investigated. We showed for the first time that protists modify soil aggregation, presumably through changes in the production of bacterial mucilage, and that collembolans reduce soil aggregation, presumably by reducing the abundance of saproptrophic fungi.
Soil aggregation is crucial for protecting soils from erosion, a major worldwide threat. While...
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