Soil nitrogen turnover and nitrous oxide emissions in continuous permafrost landscapes of Northern China in a changing climate (NIFROCLIM)
Biochemistry
Microbial Ecology and Applied Microbiology
Metabolism, Biochemistry and Genetics of Microorganisms
Final Report Abstract
In this project, soil nitrogen (N) turnover and nitrous oxide (N2O) emissions in permafrost landscapes in a changing climate were investigated. Due to an assumption of strong temperature limitation and low ecosystem inputs and availability of N according to the traditional permafrost N cycle paradigm, organic N cycling has been thought to dominate over only marginal mineral N cycling (ammonification, nitrification, denitrification). Thus, also hardly any climate change feedbacks via emissions of N2O had been expected, since these require an active mineral N cycle. However, this traditional permafrost N cycle paradigm builds on relatively little experimental evidence such as net rates of N turnover but not on measurement of gross N turnover processes. In addition, climate change, being particularly rapid in the Arctic, could amplify mineral N cycling in permafrost-affected soils. Thus, the overall goal of this project was to improve the understanding of soil biogeochemical N turnover processes in permafrost ecosystems. Field studies in the Eurasian permafrost of Northeast China and in Greenland were conducted to quantify gross N turnover across landscapes, the role of alder invasion, as well as of different fire intensities for N turnover in permafrost-affected soils. Finally, within a comprehensive synthetic meta-analysis and review we modified the traditional N cycle paradigm. This was necessary because both meta-analyses and field studies revealed the main assumptions of the traditional permafrost N cycle paradigm to be erroneous: Gross N mineralization and N2O emissions occur despite low temperatures, supported by, e.g., large N inputs via biological N2 fixation. In fact, organic N is ammonified and nitrified in active layers at large rates comparable to those in temperate and tropical systems. Permafrost-affected soils even show a very similar dependency on soil organic carbon content as a universal driver of gross N mineralization. Vigorous permafrost N cycling is confirmed by a well-adapted functional microbial community found both in active and permafrost layers. We therefore suggested a revised paradigm of permafrost N cycling with a high importance of mineral N at least in active layers and no general difference to N cycling in other soils. Also in the field study in boreal permafrost in Northeast China, significant gross mineral N turnover rates determined with in situ 15N pool dilution were detected both in mineral upland and organic lowland soils. Importantly, expansion of alders leads to a massive acceleration of the N cycle. Symbiotic input of N via Alnus-Frankia associations doubled topsoil N concentrations, thereby boosting gross ammonification and gross nitrification as well as soil N2O emissions by an order of magnitude in the sampled alder forest. As alders spread on permafrost-affected soils in the course of climate change, the described effect could trigger significant permafrost N-climate feedbacks. In addition, increasing thawing depths promote N release from formerly protected permafrost which can further increase mineral N turnover. N turnover in frozen soils and the origin of unexpected ammonium peaks close to the permafrost table are remaining research gaps. Another climate change factor are Arctic fires. Our molecular ecological studies within a fire experiment in Greenland underlined the potential role of tundra fires of low intensity but not high intensity for promoting microbes involved in N mineralization in the short term, while long-term fire effects on the microbiome need further investigation. Overall, the results of this project quantitatively reveal the unexpectedly large importance of mineral N transformations in permafrost-affected soils which will further increase through climatechange impacts. This has severe implications for Arctic ecosystem functioning in a warming climate, as more mineral N turnover might strongly increase N2O source strength, but also provide mineral nutrients for a potentially faster development of vegetation.
Publications
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From fibrous plant residues to mineral-associated organic carbon – the fate of organic matter in Arctic permafrost soils. Biogeosciences, 17(13), 3367-3383.
Prater, Isabel; Zubrzycki, Sebastian; Buegger, Franz; Zoor-Füllgraff, Lena C.; Angst, Gerrit; Dannenmann, Michael & Mueller, Carsten W.
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The Forgotten Nutrient—The Role of Nitrogen in Permafrost Soils of Northern China. Advances in Atmospheric Sciences, 37(8), 793-799.
Ramm, Elisabeth; Liu, Chunyan; Wang, Xianwei; Yue, Hongyu; Zhang, Wei; Pan, Yuepeng; Schloter, Michael; Gschwendtner, Silvia; Mueller, Carsten W.; Hu, Bin; Rennenberg, Heinz & Dannenmann, Michael
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Alder-induced acceleration of nitrogen cycling in permafrost-affected soils. Copenhagen Symposium on Arctic carbon and nitrogen dynamics, Copenhagen, Denmark, 18. – 19.03.2021.
Ramm E.; Liu C.; Mueller CW; Gschwendtner S.; Yue H.; Bachmann J.; Bohnhoff JA; Ostler U.; Schloter M.; Rennenberg H. & Dannenmann M.
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Alder-induced acceleration of nitrogen cycling in permafrost-affected soils. OZCAR-TERENO International Conference, Strasbourg, France, 04. – 08.10.2021
Ramm E.; Liu C.; Mueller CW; Gschwendtner S.; Yue H.; Bachmann J.; Bohnhoff JA; Ostler U.; Schloter M.; Rennenberg H. & Dannenmann M.
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Current research on Eurasian permafrost in Northeast China. The DFG-NSFC NIFROCLIM project 2021 International Symposium Focus Siberian Permafrost – Terrestrial Cryosphere and Climate Change, Hamburg, Germany, 24. – 25.03.2021
Ramm E.; Liu C.; Mueller CW; Gschwendtner S.; Yue H.; Bachmann J.; Bohnhoff JA; Ostler U.; Hu B.; Schloter M.; Rennenberg H.; Butterbach-Bahl K.; Rennenberg H. & Dannenmann M.
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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, Vienna, Austria, 23. – 27.05.2022. Invited and solicited presentation
Dannenmann M.; Ramm E.; Liu C.; Ambus P.; Butterbach-Bahl K.; Hu B.; Martikainen PJ; Marushchak ME; Mueller CW; Rennenberg H.; Schloter M.; Siljanen HMP; Voigt C.; Werner C. & Biasi C.
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A review of the importance of mineral nitrogen cycling in the plant-soil-microbe system of permafrost-affected soils—changing the paradigm. Environmental Research Letters, 17(1), 013004.
Ramm, Elisabeth; Liu, Chunyan; Ambus, Per; Butterbach-Bahl, Klaus; Hu, Bin; Martikainen, Pertti J.; Marushchak, Maija E.; Mueller, Carsten W.; Rennenberg, Heinz; Schloter, Michael; Siljanen, Henri M. P.; Voigt, Carolina; Werner, Christian; Biasi, Christina & Dannenmann, Michael
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Alder-induced stimulation of soil gross nitrogen turnover in a permafrost-affected peatland of Northeast China. Soil Biology and Biochemistry, 172, 108757.
Ramm, Elisabeth; Liu, Chunyan; Mueller, Carsten W.; Gschwendtner, Silvia; Yue, Hongyu; Wang, Xianwei; Bachmann, Juliane; Bohnhoff, Joost A.; Ostler, Ulrike; Schloter, Michael; Rennenberg, Heinz & Dannenmann, Michael
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Alder-induced stimulation of soil gross nitrogen turnover in permafrost-affected peatlands of Northeast China. EGU General Assembly, Vienna, Austria, 23. – 27.05.2022.
Ramm E.; Liu C.; Mueller CW; Gschwendtner S.; Yue H.; Wang X.; Bachmann J.; Bohnhoff JA; Ostler U.; Schloter M.; Rennenberg H. & Dannenmann M.
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How to Improve Cumulative Methane and Nitrous Oxide Flux Estimations of the Non‐Steady‐State Chamber Method?. Journal of Geophysical Research: Biogeosciences, 127(3).
Yue, Hongyu; Liu, Chunyan; Zhang, Wei; Dannenmann, Michael; Wang, Xianwei; Yao, Zhisheng; Song, Changchun & Butterbach‐Bahl, Klaus
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The importance of mineral nitrogen cycling in the plant-soil-microbe system of permafrost-affected soils – changing the paradigm. Invited presentation. Soil Ecology Journal Club, Department of Soil and Environment, SLU Uppsala, 10.02.2022.
Dannenmann M. & Ramm E.
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Fire intensity regulates the short-term postfire response of the microbiome in Arctic tundra soil. Geoderma, 438, 116627.
Ramm, Elisabeth; Ambus, Per Lennart; Gschwendtner, Silvia; Liu, Chunyan; Schloter, Michael & Dannenmann, Michael
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Nitrogen cycling in permafrost-affected soils in a changing climate. Dissertation submitted in fulfilment of the requirements of the degree Doctor rer. nat. of the Faculty of Environment and Natural Resources, Albert-Ludwigs-Universität Freiburg i. Breisgau, Germany. Awarded with the degree “summa cum laude”
Ramm E.
