Plant residues and fungal growth as drivers for microaggregate formation in the detritusphere

Dr Alix Vidal1, PD Dr. Markus Steffens2, Dr. Derek M. Rogge3, Dr. Gerrit Angst4, Dr. Carmen Hoeschen1, PD Dr. Carsten W. Mueller1

1TU München, Lehrstuhl für Bodenkunde, Freising, Germany, 2Research Institute of Organic Agriculture, Department of Soil Sciences, Frick, Switzerland, 3Deutsche Forschungsanstalt für Luft- und Raumfahrt, Applied spectroscopy group, Wessling, Germany, 4Institute of Soil Biology & SoWa Research Infrastructure, Biology Centre of the Czech Academy of Sciences , České Budějovic, Czech Republic

Plant residues, i.e., the detritusphere, represents a hotspot for soil structure formation. The direct vicinity of labile plant residues, microorganisms and soil minerals demonstrate the perfect microenvironment for soil aggregate formation driven by microbial products as gluing agents. However, there is a lack of experimental approaches exploring this theory in intact soil samples, considering the spatial heterogeneity of soil microstructures. We aimed at depicting the sources and vectors of organic carbon during the simultaneous formation of SOM and soil structure. To exclude possible bias in differentiating between new and inherited SOM, we used an artificial soil mixture (quartz sand, illite and goethite) free of SOM, as well as spruce needles as particulate OM. Small containers filled with the artificial soil were placed in an organic layer to allow natural microbial colonization. We studied the soil structure and OM gradient formation using spectromicroscopic imaging. We used nanoscale secondary ion mass spectroscopy with subsequent digital image processing to explore the spatial distribution of mineral (¹⁶O-, ²⁷Al¹⁶O-, ⁵⁶Fe¹⁶O-) and organic (¹²C, ¹²C¹⁴N-, ³²S-) compounds on 69 measurements. At the start of the incubation, we depicted OM free mineral surfaces in the vicinity of the needle, demonstrating the feasibility to follow subsequent OM distribution without the need of isotopic labelling. Already after 14 days, fresh OM was associated with the mineral domains surrounding the needles. After 42 days, we could demonstrate that the needles were massively infested with saprotrophic fungi, which extended into the mineral matrix of the artificial soil acting as vectors for litter derived C and N into the bulk soil. There was also an increase of the OM at greater distance to the needle and in association with mineral particles. We demonstrate the formation of micro-aggregates in the direct vicinity of plant residues as driven by microbial activity.


Dr. Alix Vidal, born 1989 in Epernay, France

7 ISI-papers with 43 citations, h-index is 4

Professional and academic career

->since 2016 – Research Assistant (Akademischer Ratin auf Zeit), Chair of soil science, Technical University of Munich

->Sep. 2016 – Dr. in Soil science, University Pierre et Marie Curie (UPMC), France

->2013 – 2016 – Doctoral candidate at UMR Metis, UPMC, France

->2013 – Dipl. Agricultural engineering, Ecole Supérieure d´Agriculture d´Angers, France

->2013 – Dipl. Agricultural engineering, Escola Superior de Agricultura « Luiz de Queiroz », São Paulo, Brazil

->2007-2013 – Study of agricultural engineering, France/Brazil

Research areas

->Soil biogeochemistry

->Biotic factors (litter type and earthworms) controlling soil organic matter decomposition

->Interactions between plant, soil and microorganisms in the rhizosphere

->Influence of organic amendments on soil characteristics

->Use of carbon stable isotope (13C) to trace carbon flows in soils

->Combination of classical quantitative (EA-IRMS, GC-MS, NMR spectroscopy) and spectromicroscopic (NanoSIMS) and imaging techniques (TEM, SEM)

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