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| Titel |
Using a trait-based approach to link microbial community composition and functioning to soil salinity |
| VerfasserIn |
Kristin Rath, Noah Fierer, Johannes Rousk |
| 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 |
250137959
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| Publikation (Nr.) |
 EGU/EGU2017-835.pdf |
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| Zusammenfassung |
| Our knowledge of the dynamics structuring microbial communities and the consequences this
has for soil functions is rudimentary. In particular, predictions of the response of
microbial communities to environmental change and the implications for associated
ecosystem processes remain elusive. Understanding how environmental factors
structure microbial communities and regulate the functions they perform is key to a
mechanistic understanding of how biogeochemical cycles respond to environmental
change.
Soil salinization is an agricultural problem in many parts of the world. The activity of soil
microorganisms is reduced in saline soils compared to non-saline soil. However, soil salinity
often co-varies with other factors, making it difficult to assign responses of microbial
communities to direct effects of salinity. A trait-based approach allows us to connect the
environmental factor salinity with the responses of microbial community composition and
functioning. Salinity along a salinity gradient serves as a filter for the community trait
distribution of salt tolerance, selecting for higher salt tolerance at more saline sites. This
trait-environment relationship can be used to predict responses of microbial communities to
environmental change.
Our aims were to (i) use salinity along natural salinity gradients as an environmental
filter, and (ii) link the resulting filtered trait-distributions of the communities (the trait being
salt tolerance) to the community composition.
Soil samples were obtained from two replicated salinity gradients along an Australian salt
lake, spanning a wide range of soil salinities (0.1 dS m−1 to >50 dS m−1). In one of the two
gradients salinity was correlated with pH. Community trait distributions for salt tolerance
were assessed by establishing dose-dependences for extracted bacterial communities using
growth rate assays. In addition, functional parameters were measured along the salt gradients.
Community composition of sites was compared through 16S rRNA gene amplicon
sequencing.
Microbial community composition changed greatly along the salinity gradients. Using the
salt-tolerance assessments to estimate bacterial trait-distributions we could determine
substantial differences in tolerance to salt revealing a strong causal connection between
environment and trait distributions. By constraining the community composition with salinity
tolerance in ordinations, we could assign which community differences were directly due to a
shift in community trait distributions. These analyses revealed that a substantial part (up to
30%) of the community composition differences were directly driven by environmental salt
concentrations.. Even though communities in saline soils had trait-distributions
aligned to their environment, their performance (respiration, growth rates) was
lower than those in non-saline soils and remained low even after input of organic
material.
Using a trait-based approach we could connect filtered trait distributions along
environmental gradients, to the composition of the microbial community. We show that soil
salinity played an important role in shaping microbial community composition by selecting
for communities with higher salt tolerance. The shift toward bacterial communities with trait
distributions matched to salt environments probably compensated for much of the potential
loss of function induced by salinity, resulting in a degree of apparent functional
redundancy for decomposition. However, more tolerant communities still showed
reduced functioning, suggesting a trade-off between salt tolerance and performance. |
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