Robert Brankatschk (ETH Zürich, Switzerland), Stefanie Töwe, Kristina Kleineidam, Michael Schloter & Josef Zeyer
"Mineralization not Nitrogen Fixation Drives Nitrogen Turnover of the Youngest Soils in the forefield of the Receding Damma Glacier, Switzerland"


Forefields of receding glaciers represent ideal ecosystems to study the development of the nitrogen (N) cycle. We studied the development of the N cycling microbial community in the soil chronosequence of the Damma glacier, Switzerland. Bulk soil of five different ages was sampled. Four N cycling processes were quantitatively assessed, first on protein-level by potential enzyme activity and second on DNA-level by abundance of functional genes. The functional genes studied, corresponded to the four N transformation processes: N fixation (nifH), mineralization (chiA and aprA), nitrification (amoA) and denitrification (nirK, nirS, and nosZ). Our results suggest that mineralization drives nitrogen turnover in the very initial soil system (10 years), before N fixation establishes (50 years and onwards). In late succession (120 years) the N cycle is closed, i.e. the processes N-fixation, mineralization, nitrification and denitrification are all participating in N turnover.