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| Titel |
Experimental evidence of the role of pores on movement and distribution of bacteria in soil |
| VerfasserIn |
Alexandra N. Kravchenko, Joan B. Rose, Terence L. Marsh, Andrey K. Guber |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250089681
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| Publikation (Nr.) |
 EGU/EGU2014-3891.pdf |
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| Zusammenfassung |
| It has been generally recognized that micro-scale heterogeneity in soil environments can have
a substantial effect on movement, fate, and survival of soil microorganisms. However,
only recently the development of tools for micro-scale soil analyses, including
X-ray computed micro-tomography (μ-CT), enabled quantitative analyses of these
effects. The long-term goal of our work is to explore how differences in micro-scale
characteristics of pore structures influence movement, spatial distribution patterns, and
activities of soil microorganisms. Using X-ray μ-CT we found that differences in
land use and management practices lead to development of contrasting patterns in
pore size-distributions within intact soil aggregates. Then our experiments with
Escherichia coli added to intact soil aggregates demonstrated that the differences in
pore structures can lead to substantial differences in bacteria redistribution and
movement within the aggregates. Specifically, we observed more uniform E.coli
redistribution in aggregates with homogeneously spread pores, while heterogeneous pore
structures resulted in heterogeneous E.coli patterns. Water flow driven by capillary
forces through intact aggregate pores appeared to be the main contributor to the
movement patterns of the introduced bacteria. Influence of pore structure on E.coli
distribution within the aggregates further continued after the aggregates were subjected to
saturated water flow. E. coli’s resumed movement with saturated water flow and
subsequent redistribution within the soil matrix was influenced by porosity, abundance of
medium and large pores, pore tortuosity, and flow rates, indicating that greater
flow accompanied by less convoluted pores facilitated E. coli transport within the
intra-aggregate space. We also found that intra-aggregate heterogeneity of pore structures can
have an effect on spatial distribution patterns of indigenous microbial populations.
Preliminary analysis showed that in aggregates from an organic agricultural system with
cover crops, characterized by greater intra-aggregate pore heterogeneity, bacteria of
Actinobacteria and Firmicutes groups were more abundant in presence of large as compared
to small pores. In contrast, no differences were observed in the aggregates from
conventionally managed soil, overall characterized by homogeneous intra-aggregate pore
patterns. Further research efforts are being directed towards quantification of the pore
structure effects on activities and community composition of soil microorganisms. |
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