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| Titel |
Assessing the soil microbial carbon budget: Probing with salt stress |
| VerfasserIn |
Kristin Rath, Johannes Rousk |
| 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 |
250092558
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| Publikation (Nr.) |
 EGU/EGU2014-6911.pdf |
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| Zusammenfassung |
| The amount of carbon stored as soil organic matter (SOM) constitutes a pool more than
double the size of the atmospheric carbon pool. Soil respiration represents one of the largest
fluxes of carbon between terrestrial ecosystems and the atmosphere. A large fraction of the
CO2 released by soils is produced by the microbial decomposition of SOM. The microbial
carbon budget is characterized by their carbon use efficiency, i.e. the partitioning of substrate
into growth and respiration. This will shape the role of the soil as a net source or sink for
carbon. One of the canonical factors known to influence microbial processes in soil is pH. In
aquatic systems salinity has been found to have a comparably strong influence as pH.
However salinity remains understudied in soil, despite its growing relevance due to land use
change and agricultural practices.
The aim of this project is to understand how microbial carbon dynamics respond to
disturbance by changing environmental conditions, using salinity as a reversible stressor.
First, we compiled a comparative analysis of the sensitivity of different microbial processes
to increasing salt concentrations. Second, we compared different salts to determine whether
salt toxicity depended on the identity of the salt. Third, we used samples from a natural
salinity gradient to assess if a legacy of salt exposure can influence the microbial response to
changing salt concentrations. If salt had an ecologically significant effect in shaping these
communities, we would assume that microbial processes would be less sensitive to an
increase in salt concentrations.
The sensitivity of microbial processes to salt was investigated by establishing inhibition
curves in order to estimate EC50 values (the concentration resulting in 50% inhibition). These
EC50 values were used to compare bacterial and fungal growth responses, as well as
catabolic processes such as respiration and nitrogen mineralisation. Initial results
suggest that growth related measures are more sensitive to salinity than catabolic
processes. This could be an indication that at higher salt concentrations, the microbial
community allocates less carbon towards growth, resulting in reduced carbon use
efficiency. We also found that microbial processes show different sensitivities depending
on the kind of salt used in the experiment. Currently we are making comparative
analyses to determine whether osmotic strength or specific ion concentrations best
explain toxicity. In addition we are in the process of investigating if pre-exposed
communities from naturally saline soils have developed a higher tolerance to salt. |
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