Кл.слова (ненормированные):
Arctic -- Cryoturbation -- Ecological stoichiometry -- Nitrification -- Nitrogen availability -- Nitrogen mineralization -- Nitrogen transformation -- Protein depolymerization -- Soil organic matter -- Tundra -- Arctic -- Cryoturbation -- Ecological stoichiometry -- Nitrogen availability -- Nitrogen mineralization -- Nitrogen transformations -- Protein depolymerization -- Soil organic matters -- Tundra -- Amino acids -- Biogeochemistry -- Decay (organic) -- Depolymerization -- Mineralogy -- Nitrification -- Nitrogen -- Organic compounds -- Permafrost -- Proteins -- Soils -- arctic environment -- cryoturbation -- decomposition -- freezing -- microbial community -- mineralization -- nitrification -- nitrogen -- nitrogen cycle -- permafrost -- protein -- soil horizon -- soil organic matter -- stoichiometry -- subsoil -- thawing -- transformation -- tundra -- Arctic -- Greenland -- Siberia
Аннотация: 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. В© 2013 The Authors.
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Держатели документа:
University of Vienna, Department of Microbiology and Ecosystem Science, Division of Terrestrial Ecosystem Research, Althanstrasse 14, 1090 Vienna, Austria
Austrian Polar Research Institute, 1090 Vienna, Austria
University of South Bohemia, Department of Ecosystems Biology, Branisovska 31, 37005 Ceske Budejovice, Czech Republic
Leibniz Universitat Hannover, Institut fur Bodenkunde, Herrenhauser Strasse 2, 30419 Hannover, Germany
International Institute for Applied Systems Analysis (IIASA), Schlossplatz 1, 2361 Laxenburg, Austria
Central Siberian Botanical Garden, Siberian Branch of Russian Academy of Sciences, St. Zolotodolinskaya 101, 630090 Novosibirsk, Russian Federation
VN Sukachev Institute of Forest, Siberian Branch of Russian Academy of Sciences, Akademgorodok, 660036 Krasnoyarsk, Russian Federation
University of Vienna, Department of Ecogenomics and Systems Biology, Althanstrasse 14, 1090 Vienna, Austria
University of Bergen, Department of Biology/Centre for Geobiology, Allegaten 41, 5007 Bergen, Norway
Northeast Scientific Station, Pacific Institute for Geography, Far-East Branch of Russian Academy of Sciences, 678830 Chersky, Republic of Sakha, Russian Federation
Доп.точки доступа:
Wild, B.; Schnecker, J.; Barta, J.; Capek, P.; Guggenberger, G.; Hofhansl, F.; Kaiser, C.; Lashchinsky, N.; Mikutta, R.; Mooshammer, M.; Santruckova, H.; Shibistova, O.; Urich, T.; Zimov, S.A.; Richter, A.