A review of the importance of mineral nitrogen cycling in the plant-soil-microbe system of permafrost-affected soils – changing the paradigm
- 1Karlsruhe Institute of Technology IMK-IFU, Biosphere-Atmosphere interactions under Global Change, D-82467 Garmisch-Partenkirchen, Germany (michael.dannenmann@kit.edu)
- 2State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences (CAS), Beijing 100029, People’s Republic of China
- 3Department of Geosciences and Natural Resource Management, Center for Permafrost (Cenperm), University of Copenhagen, Copenhagen DK-1350, Denmark
- 4Center of Molecular Ecophysiology (CMEP), College of Resources and Environment, Southwest University, Chongqing 400715, People’s Republic of China
- 5Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio 70210, Finland
- 6Department of Biological and Environmental Science, University of Jyväskylä, Jyväskylä FI-40014, Finland
- 7Chair of Soil Science, Science Center Weihenstephan, Department of Ecology and Ecosystem Management, Technical University Munich, Freising 85354, Germany
- 8Research Unit for Comparative Microbiome Analyses, Helmholtz Zentrum München, Oberschleissheim 85764, Germany
- 9Department of Geography, University of Montreal, Montreal, QC H2V 0B3, Canada
The paradigm that permafrost-affected soils show restricted mineral nitrogen (N) cycling in favor of organic N compounds is based on the observation that net N mineralization rates in these cold climates are negligible. However, we find here that this perception is wrong. By synthesizing published data on N cycling in the plant-soil-microbe system of permafrost ecosystems we show that gross ammonification and nitrification rates in active layers were of similar magnitude and showed a similar dependence on soil organic carbon (C) and total N concentrations as observed in temperate and tropical systems. Moreover, high protein depolymerization rates and only marginal effects of C:N stoichiometry on gross N turnover provided little evidence for N limitation. Instead, the rather short period when soils are not frozen is the single main factor limiting N turnover. High gross rates of mineral N cycling are thus facilitated by released protection of organic matter in active layers with nitrification gaining particular importance in N-rich soils, such as organic soils without vegetation. Our finding that permafrost-affected soils show vigorous N cycling activity is confirmed by the rich functional microbial community which can be found both in active and permafrost layers. The high rates of N cycling and soil N availability are supported by biological N fixation, while atmospheric N deposition in the Arctic still is marginal except for fire-affected areas. In line with high soil mineral N production, recent plant physiological research indicates a higher importance of mineral plant N nutrition than previously thought.
Our synthesis shows that mineral N production and turnover rates in active layers of permafrost-affected soils do not generally differ from those observed in temperate or tropical soils. We therefore suggest to adjust the permafrost N cycle paradigm, assigning a generally important role to mineral N cycling. This new paradigm suggests larger permafrost N climate feedbacks than assumed previously.
How to cite: Dannenmann, M., Ramm, E., Liu, C., Ambus, P., Butterbach-Bahl, K., Hu, B., Martikainen, P. J., Marushchak, M. E., Mueller, C. W., Rennenberg, H., Schloter, M., Siljanen, H. M. P., Voigt, C., Werner, C., and Biasi, C.: A review of the importance of mineral nitrogen cycling in the plant-soil-microbe system of permafrost-affected soils – changing the paradigm, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-11621, https://doi.org/10.5194/egusphere-egu22-11621, 2022.
