TY - JOUR

T1 - Visualizing the transfer of organic matter from decaying plant residues to soil mineral surfaces controlled by microorganisms

AU - Vidal, Alix

AU - Klöffel, Tobias

AU - Guigue, Julien

AU - Angst, Gerrit

AU - Steffens, Markus

AU - Hoeschen, Carmen

AU - Mueller, Carsten W.

N1 - Funding Information: This work was financially supported by the Deutsche Forschungsgemeinschaft in the frame of the DFG research unit FOR1806 ?The forgotten part of carbon cycling: Soil organic matter storage and turnover in subsoils (SUBSOM)? [grant number MU 3021/4-1]. We also thank Dominik Fiedler from Fraunhofer-Institut for the support with the SEM analyses. We acknowledge Gertraud Harrington and Johann Lugmeier for technical support related to NanoSIMS measurements, and Lukas Heinrich for his help with the maintenance of the experiment. We also thank Derek Rogge for his preliminary advices on digital image processing and the DFG for funding the NanoSIMS instrument [grant number KO 1035/38-1]. Funding Information: This work was financially supported by the Deutsche Forschungsgemeinschaft in the frame of the DFG research unit FOR1806 “The forgotten part of carbon cycling: Soil organic matter storage and turnover in subsoils (SUBSOM)” [grant number MU 3021/4-1 ]. We also thank Dominik Fiedler from Fraunhofer-Institut for the support with the SEM analyses. We acknowledge Gertraud Harrington and Johann Lugmeier for technical support related to NanoSIMS measurements, and Lukas Heinrich for his help with the maintenance of the experiment. We also thank Derek Rogge for his preliminary advices on digital image processing and the DFG for funding the NanoSIMS instrument [grant number KO 1035/38-1 ]. Publisher Copyright: © 2021 Elsevier Ltd

PY - 2021/9

Y1 - 2021/9

N2 - The interface between decaying plant residues and soil minerals represents an essential soil microenvironment at which soil organic matter forms. The high amount of microbial products and residues within this hot spot of microbial activity fosters the formation of mineral-associated organic matter. Besides classical quantitative analyses, our understanding of processes controlling soil organic matter formation greatly benefits from microscopic observations and measurements, which provide spatially resolved information at a meaningful scale for microbial processes and for the association between organic and mineral particles. We studied carbon and nitrogen transfer from fresh-plant residues to the mineral soil, through a litter decomposition experiment in an artificial soil mixture. Needles of Norway spruce (Picea abies L.) were placed in microbatch containers filled with an artificial soil mixture free of soil organic matter. Containers were buried in fresh organic layer material from a Norway spruce stand and incubated for 14 and 42 days. We applied nanoscale secondary ion mass spectroscopy (NanoSIMS) to investigate the spatial distribution of mineral and organic compounds at the needle vicinity and into the mineral soil (0–550 μm from the needle). After 14 days, we depicted the formation of mineral-associated organic matter in the surrounding of the decaying needles. After 42 days, we observed substantial colonization of the needles and the detritusphere by saprotrophic fungi. The fungal hyphae extended into the mineral matrix of the artificial soil acting as vectors for the transfer of litter-derived carbon and nitrogen into the bulk soil. This resulted in an increase of the area covered by organic matter in the detritusphere, with up to 10% of the total investigated area classified as organic matter closely associated with mineral surfaces. Our results provide evidence that the carbon and nitrogen derived from litter decomposition transformed by microorganisms is transferred as mineral-associated organic matter, heterogeneously distributed from the litter source, and still detected 550 μm away from the latter. The close association of newly formed soil organic matter and fine sized minerals suggests that the formation of mineral-associated OM and likely also microaggregates is directly driven by microbial activity in the vicinity of hot spots for plant carbon input (e.g. the detritusphere).

AB - The interface between decaying plant residues and soil minerals represents an essential soil microenvironment at which soil organic matter forms. The high amount of microbial products and residues within this hot spot of microbial activity fosters the formation of mineral-associated organic matter. Besides classical quantitative analyses, our understanding of processes controlling soil organic matter formation greatly benefits from microscopic observations and measurements, which provide spatially resolved information at a meaningful scale for microbial processes and for the association between organic and mineral particles. We studied carbon and nitrogen transfer from fresh-plant residues to the mineral soil, through a litter decomposition experiment in an artificial soil mixture. Needles of Norway spruce (Picea abies L.) were placed in microbatch containers filled with an artificial soil mixture free of soil organic matter. Containers were buried in fresh organic layer material from a Norway spruce stand and incubated for 14 and 42 days. We applied nanoscale secondary ion mass spectroscopy (NanoSIMS) to investigate the spatial distribution of mineral and organic compounds at the needle vicinity and into the mineral soil (0–550 μm from the needle). After 14 days, we depicted the formation of mineral-associated organic matter in the surrounding of the decaying needles. After 42 days, we observed substantial colonization of the needles and the detritusphere by saprotrophic fungi. The fungal hyphae extended into the mineral matrix of the artificial soil acting as vectors for the transfer of litter-derived carbon and nitrogen into the bulk soil. This resulted in an increase of the area covered by organic matter in the detritusphere, with up to 10% of the total investigated area classified as organic matter closely associated with mineral surfaces. Our results provide evidence that the carbon and nitrogen derived from litter decomposition transformed by microorganisms is transferred as mineral-associated organic matter, heterogeneously distributed from the litter source, and still detected 550 μm away from the latter. The close association of newly formed soil organic matter and fine sized minerals suggests that the formation of mineral-associated OM and likely also microaggregates is directly driven by microbial activity in the vicinity of hot spots for plant carbon input (e.g. the detritusphere).

KW - Artificial soil mixture

KW - Microaggregates

KW - Mineral-associated organic matter

KW - NanoSIMS

KW - Norway spruce

KW - Saprotrophic fungi

U2 - 10.1016/j.soilbio.2021.108347

DO - 10.1016/j.soilbio.2021.108347

M3 - Journal article

AN - SCOPUS:85109104295

VL - 160

JO - Soil Biology & Biochemistry

JF - Soil Biology & Biochemistry

SN - 0038-0717

M1 - 108347

ER -