Nitrogen dynamics in Turbic Cryosols from Siberia and Greenland
Creators: name: Wild, Birgit
name: Schnecker, Jörg
name: Bárta, Jiri
name: Čapek, Petr
name: Guggenberger, Georg
name: Hofhansl, Florian
name: Kaiser, Christina
name: Lashchinskiy, Nikolay
name: Mikutta, Robert
name: Mooshammer, Maria
name: Šantrůčková, Hana
name: Shibistova, Olga
name: Urich, Tim
name: Zimov, Sergey A.
name: Richter, Andreas
Publisher: name: Amsterdam : Elsevier
Year: 2013
Subjects: subject: Arctic
subject: Cryoturbation
subject: Ecological stoichiometry
subject: Nitrification
subject: Nitrogen availability
subject: Nitrogen mineralization
subject: Nitrogen transformation
subject: Protein depolymerization
subject: Soil organic matter
subject: Tundra
subject: Nitrogen transformations
subject: Soil organic matters
subject: Amino acids
subject: Biogeochemistry
subject: Decay (organic)
subject: Depolymerization
subject: Mineralogy
subject: Nitrogen
subject: Organic compounds
subject: Permafrost
subject: Proteins
subject: Soils
subject: arctic environment
subject: cryoturbation
subject: decomposition
subject: freezing
subject: microbial community
subject: mineralization
subject: nitrification
subject: nitrogen
subject: nitrogen cycle
subject: permafrost
subject: protein
subject: soil horizon
subject: soil organic matter
subject: stoichiometry
subject: subsoil
subject: thawing
subject: transformation
subject: tundra
subject: Greenland
subject: Siberia
subject: Dewey Decimal Classification::500 | Naturwissenschaften::570 | Biowissenschaften, Biologie

description: Turbic Cryosols (permafrost soils characterized by cryoturbation, i.e., by mixing of soil layers due to freezing and thawing) are widespread across the Arctic, and contain large amounts of poorly decomposed organic material buried in the subsoil. This cryoturbated organic matter exhibits retarded decomposition compared to organic material in the topsoil. Since soil organic matter (SOM) decomposition is known to be tightly linked to N availability, we investigated N transformation rates in different soil horizons of three tundra sites in north-eastern Siberia and Greenland. We measured gross rates of protein depolymerization, N mineralization (ammonification) and nitrification, as well as microbial uptake of amino acids and NH4 + using an array of 15N pool dilution approaches. We found that all sites and horizons were characterized by low N availability, as indicated by low N mineralization compared to protein depolymerization rates (with gross N mineralization accounting on average for 14% of gross protein depolymerization). The proportion of organic N mineralized was significantly higher at the Greenland than at the Siberian sites, suggesting differences in N limitation. The proportion of organic N mineralized, however, did not differ significantly between soil horizons, pointing to a similar N demand of the microbial community of each horizon. In contrast, absolute N transformation rates were significantly lower in cryoturbated than in organic horizons, with cryoturbated horizons reaching not more than 32% of the transformation rates in organic horizons. Our results thus indicate a deceleration of the entire N cycle in cryoturbated soil horizons, especially strongly reduced rates of protein depolymerization (16% of organic horizons) which is considered the rate-limiting step in soil N cycling.