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| Titel |
Microbial diversity and biogeochemistry in glacier forefields: assessment of ecological stability in high alpine environments |
| VerfasserIn |
M. Meola, A. Lazzaro, J. Zeyer |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250066945
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| Zusammenfassung |
| Microbial communities inhabiting recently deglaciated, unvegetated, high alpine soils
(e.g. glacier forefields) need to be adapted to fluctuating environmental conditions,
such as strong daily and seasonal humidity and temperature variations. Soil-related
characteristics (e.g. oligotrophy, pH, water holding capacity, nutrient concentration) may in
addition determine the presence of locally adapted microbial communities. Currently
little is known on the ecological stability (resistance and resilience) of such an
environment.
In this project, we aim at understanding ecological stability of microbial communities of
alpine glacier forefields through a reciprocal soil transplantation experiment. The study
consists in i) determining bacterial phylotypes that may respond to environmental
changes and ii) relating biological, chemical and physical data to observed microbial
responses.
We selected two different glacier forefields located in the Swiss Alps (approximately at
2500 m.a.s.l.) The Griessen forefield (Canton Obwalden) is characterized by a calcareous
bedrock, while the Tiefen forefield (Canton Uri) is of siliceous composition. The sites are
well characterized in terms of their geography (e.g. exposure, slope) and climatic
fluctuations (Lazzaro et al. 2009, Lazzaro et al. 2011). At each site, we incubated
stainless steel pots with four different soil treatments (autochthonous untreated,
autochthonous sterilized, allochthonous untreated and allochthonous sterilized). The
setup was repeated in quadruplicate. Soil temperature and soil moisture at 10 cm
depth were measured every hour by Decagon EM 50 sensors (Decagon Devices
Inc.).
In July (D0), August (D1) and September (D2) 2011, soil aliquots were sampled from the
pots for analysis. We plan to further extend the sampling for at least three snow-free seasons
(2011-2013). Chemical analysis of the soil encompassed soluble ions, pH and DOC. Bacterial
community analysis included microbial biomass (DAPI cell counts), basal activity
(microcalorimetry) and community structures (Terminal-Restriction Fragment Length
Polymorphism (T-RFLP) profiling of the 16S rRNA gene).
DOC concentrations were within the range of values reported from other glacier forefields
(< 0.5 mg [g soil dry wt.]-1) and suggested an oligotrophic character of the soils. Nitrate
concentrations were apparently not affected by the sterilization but slightly by the
transplantation. The nitrate concentration fluctuated strongly from D0 to D3 in a range
between approximately 10 – 30 μg NO3- [g soil dry wt.]-1. Ammonium concentrations
were higher (1.5 – 4 μg NH4+ [g soil dry wt.]-1) in all samples incubating at Griessen.
Neither transplantation nor sterilization had an effect on ammonium concentration. T-RFLP
analysis showed that the bacterial communities from both soils changed with both the
transplantation and time. Moreover, in all sterilized samples, we could observe a gradual
increase in operational taxonomic unit (OTU) richness from D0 to D1 and D2. Ongoing
analyses, based on the association of T-RFLP profiles and clone libraries, will allow
identifying the main phylotypes involved in the community changes and in the colonization
processes.
In conclusion, this experimental setup allowed a detailed monitoring of changes of
physico-chemical soil properties and of in situ microbial responses. Resistance and resilience
will be quantified according to community changes observed in the untreated and sterilized
soils at different sampling timepoints.
Lazzaro A., Abegg C., Zeyer J. (2009). Bacterial community structure of glacier
forefields on siliceous and calcareous bedrock. European Journal of Soil Science, 60:
860–870.
Lazzaro A., R. Brankatschk,., Zeyer J. (2011). Seasonal dynamics of nutrients and
bacterial communities in unvegetated alpine glacier forefields. Applied Soil Ecology. 53:
10-22. |
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