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| Titel |
Microscale soil structure development after glacial retreat -- using
machine-learning based segmentation of elemental distributions obtained by
NanoSIMS |
| VerfasserIn |
Steffen Schweizer, Steffen Schlueter, Carmen Hoeschen, Ingrid Koegel-Knabner, Carsten W. Mueller |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250141028
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| Publikation (Nr.) |
 EGU/EGU2017-4489.pdf |
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| Zusammenfassung |
| Soil organic matter (SOM) is distributed on mineral surfaces depending on physicochemical
soil properties that vary at the submicron scale. Nanoscale secondary ion mass spectrometry
(NanoSIMS) can be used to visualize the spatial distribution of up to seven elements
simultaneously at a lateral resolution of approximately 100 nm from which patterns of SOM
coatings can be derived. Existing computational methods are mostly confined to visualization
and lack spatial quantification measures of coverage and connectivity of organic matter
coatings. This study proposes a methodology for the spatial analysis of SOM coatings
based on supervised pixel classification and automatic image analysis of the 12C,
12C14N (indicative for SOM) and 16O (indicative for mineral surfaces) secondary ion
distributions. The image segmentation of the secondary ion distributions into mineral
particle surface and organic coating was done with a machine learning algorithm,
which accounts for multiple features like size, color, intensity, edge and texture in all
three ion distributions simultaneously. Our workflow allowed the spatial analysis of
differences in the SOM coverage during soil development in the Damma glacier
forefield (Switzerland) based on NanoSIMS measurements (n=121; containing
ca. 4000 particles). The Damma chronosequence comprises several stages of soil
development with increasing ice-free period (from ca. 15 to >700 years). To investigate
mineral-associated SOM in the developing soil we obtained clay fractions (<2 μm)
from two density fractions: light mineral (1.6 to 2.2 g cm3) and heavy mineral
(>2.2 g cm3). We found increased coverage and a simultaneous development from
patchy-distributed organic coatings to more connected coatings with increasing time after
glacial retreat. The normalized N:C ratio (12C14N: (12C14N + 12C)) on the organic matter
coatings was higher in the medium-aged soils than in the young and mature ones in
both heavy and light mineral fraction. This reflects the sequential accumulation of
proteinaceous SOM in the medium-aged soils and C-rich compounds in the mature
soils. The results of our microscale image analysis correlated well with the SOM
concentration of the fractions measured by elemental analyzer. Image analysis in
combination with secondary ion distributions provides a powerful tool at the required
microscale and enhances our mechanistic understanding of SOM stabilization in soil. |
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