Vom Einzelprozess zum Zyklus: Die Entstehung von Stickstoff-Umsetzungsprozessen in terrestrischen Ökosystemen der maritimen Antarktis
Zusammenfassung der Projektergebnisse
Many studies investigating initial ecosystems reported diverse heterotrophic communities in newly exposed substrates feeding on ancient and allochthonous carbon and air-deposited nitrogen before autotrophic succession starts. This situation might be different in Antarctic ecosystems due to the lack of continuous N deposition, resulting in nitrogen fixation as main source of additional N input into soil. The aim of this project was to investigate (i) the establishment of nitrogen turnover processes and their microbial drivers along a succession gradient of differently developed soils in the maritime Antarctic, with special focus on processes related to nitrogen input (N fixation), recycling (DNRA) and losses (nitrification and denitrification) and (ii) the linking of different nutrient cycles, especially N and P turnover processes. To overcome the spatial heterogeneity of Antarctic habitats, two soil chronosequences defined by different deglaciation schemes and two soil depths were investigated. Our data revealed that: (i) Despite the occurrence of a heterotrophic community, nitrogen fixation and DNRA was highest in initial sites but decreased with soil age, whereas nitrification and denitrification increased. Furthermore, clear shifts in functional microbial community related to succession stage and soil depth were observed for all processes. Whereas sequences related to N2 fixation and nitric oxide reduction (norB) mainly derived from various Proteobacteria, sequences related to nitrous oxide reduction (nosZ) originated from different phyla including Bacteroidetes, Chloroflexi, Firmicutes, Gemmatimonadetes, Proteobacteria, Verrucomicrobia, Euryarchaeota and Crenarchaeota. Similarly, genes of the functionally redundant enzymes catalyzing DNRA were differently distributed among microbial taxa, with nirBD being present in various taxonomic classes but nrfA mainly in Deltaproteobacteria. (ii) Genes related to phosphorous turnover processes are abundant in the microbial community. However, while pioneer taxa like Cyanobacteria harbor both genes encoding for P uptake and P mineralization other taxa might “specialize” on either uptake or mineralization.
Projektbezogene Publikationen (Auswahl)
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“Establishment and evolution of microbial communities during ecosystem development” (SCAR Conference 2017, Poster)
Gschwendtner S.; Boy J. & Godoy R.
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“Establishment of functional microbial communities and nutrient cycling processes during ecosystem development” (PAM Conference 2017, Poster)
Gschwendtner S.; Boy J. & Godoy R.
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“Establishment of microbial communities and nutrient turnover processes during ecosystem development in the maritime Antarctic” (ISME17 Conference 2018, Poster)
Gschwendtner S.; Boy J.; Godoy R. & Schloter M.
