Preprints
https://doi.org/10.5194/soil-2016-73
https://doi.org/10.5194/soil-2016-73
18 Nov 2016
 | 18 Nov 2016
Status: this preprint was under review for the journal SOIL. A revision for further review has not been submitted.

Two different microbial communities did not cause differences in occlusion of particulate organic matter in a sandy agricultural soil

Frederick Büks, Philip Rebensburg, Peter Lentzsch, and Martin Kaupenjohann

Abstract. Apart from physico-chemical interactions between soil components, microbial life is assumed to be an important factor of soil structure forming processes. Bacterial exudates, the entanglement by fungal hypae and bacterial pseudomycelia as well as fungal glomalin are supposed to provide the occlusion of particulate organic matter (POM) through aggregation of soil particles.

This work investigates the resilience of POM occlusion in face of different microbial communities under controlled environmental conditions. We hypothesized that the formation of different communities would cause different grades of POM occlusion. For this purpose samples of a sterile sandy agricultural soil were incubated for 76 days in bioreactors. Particles of pyrochar from pine wood were added as POM analogue. One variant was inoculated with a native soil extract, whereas the control was infected by airborne microbes. A second control soil remained non-incubated. During the incubation, soil samples were taken for taxon-specific qPCR to determine the abundance of Eubacteria, Fungi, Archaea, Acidobacteria, Actinobacteria, α-Proteobacteria and β-Proteobacteria. After the incubation soil aggregates (100–2000 μm) were collected by sieving and disaggregated using ultrasound to subject the released POM to an analysis of organic carbon (OC).

Our results show, that the eubacterial DNA of both incubated variants reached a similar concentration after 51 days. However, the structural composition of the two communities was completely different. The soil-born variant was dominated by Acidobacteria, Actinobacteria and an additional fungal population, whereas the air-born variant mainly contained β-Proteobacteria. Both variants showed a strong occlusion of POM into aggregates during the incubation. Yet, despite the different population structure, there were only marginal differences in the release of POM along with the successive destruction of soil aggregates by ultrasonication. This leads to the tentative assumption that POM occlusion in agricultural soils could be resilient in face of changing microbial communities.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Frederick Büks, Philip Rebensburg, Peter Lentzsch, and Martin Kaupenjohann
 
Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed (peer review stopped)
Status: closed (peer review stopped)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Frederick Büks, Philip Rebensburg, Peter Lentzsch, and Martin Kaupenjohann
Frederick Büks, Philip Rebensburg, Peter Lentzsch, and Martin Kaupenjohann

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Short summary
Microbial communities play a role in soil aggregate formation. However, the influence of the microbial community structure on POM occlusion within soil aggregates is still unproved. In this experiment, sterile sandy agricultural soil was incubated in two variants – inoculated with soil extract and infected with air-born microorganisms. After 76 days of incubation soils show a strongly differing microbial populations structure, but no significant difference in POM occlusion.