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| Titel |
Microbial carbon turnover in the plant-rhizosphere-soil continuum |
| VerfasserIn |
Ashish Malik, Helena Dannert, Robert Griffiths, Bruce Thomson, Gerd Gleixner |
| 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 |
250096748
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| Publikation (Nr.) |
 EGU/EGU2014-12265.pdf |
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| Zusammenfassung |
| Soil microbial biomass contributes significantly to maintenance of soil organic matter (SOM).
It is well known that biochemical fractions of soil microorganisms have varying turnover and
therefore contribute differentially to soil C storage. Here we compare the turnover rates of
different microbial biochemical fractions using a pulse chase 13CO2 plant labelling
experiment. The isotope signal was temporally traced into rhizosphere soil microorganisms
using the following biomarkers: DNA, RNA, fatty acids and chloroform fumigation
extraction derived microbial biomass size classes. C flow into soil microbial functional
groups was assessed through phospholipid and neutral lipid fatty acid (PLFA/NLFA)
analyses. Highest 13C enrichment was seen in the low molecular weight (LMW)
size class of microbial biomass (Δδ13C =151) and in nucleic acids (DNA: 38o
RNA: 66) immediately after the pulse followed by a sharp drop. The amount of 13C
in the high molecular weight (HMW) microbial biomass (17-81) and total fatty
acids (32-54) was lower initially and stayed relatively steady over the 4 weeks
experimental period. We found significant differences in turnover rates of different
microbial biochemical and size fractions. We infer that LMW cytosolic soluble
compounds are rapidly metabolized and linked to respiratory C fluxes, whereas mid-sized
products of microbial degradation and HMW polymeric compounds have lower
renewal rate in that order. The turnover of cell wall fatty acids was also very slow.
DNA and RNA showed faster turnover rate; and as expected RNA renewal was
the fastest due to its rapid production by active microorganisms independent of
cell replication. 13C incorporation into different functional groups confirmed that
mutualistic arbuscular mycorrhizal fungi rely on root C and are important in the initial
plant C flux. We substantiated through measurements of isotope incorporation into
bacterial RNA that rhizosphere bacteria are also important in the initial C conduit from
plants. Other saprophytic fungi and bacteria show a delayed 13C incorporation
pattern which could suggest secondary 13C assimilation often indicative of trophic
interactions. Thus, different soil microbial biochemical fractions as well as functional
groups show differential C turnover which could have implications on soil C storage. |
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