Amino acid production exceeds plant nitrogen demand in Siberian tundra

Wild, Birgit and Alves, Ricardo J. Eloy and Barta, Jiri and Capek, Petr and Gentsch, Norman and Guggenberger, Georg and Hugelius, Gustaf and Knoltsch, Anna and Kuhry, Peter and Lashchinskiy, Nikolay and Mikutta, Robert and Palmtag, Juri and Prommer, Judith and Schnecker, Joerg and Shibistova, Olga and Takriti, Mounir and Urich, Tim and Richter, Andreas (2018) Amino acid production exceeds plant nitrogen demand in Siberian tundra. Environmental Research Letters, 13 (3). ISSN 1748-9326

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Abstract

Arctic plant productivity is often limited by low soil N availability. This has been attributed to slow breakdown of N-containing polymers in litter and soil organic matter (SOM) into smaller, available units, and to shallow plant rooting constrained by permafrost and high soil moisture. Using N-15 pool dilution assays, we here quantified gross amino acid and ammonium production rates in 97 active layer samples from four sites across the Siberian Arctic. We found that amino acid production in organic layers alone exceeded literature-based estimates of maximum plant N uptake 17-fold and therefore reject the hypothesis that arctic plant N limitation results from slow SOM breakdown. High microbial N use efficiency in organic layers rather suggests strong competition of microorganisms and plants in the dominant rooting zone. Deeper horizons showed lower amino acid production rates per volume, but also lower microbial N use efficiency. Permafrost thaw together with soil drainage might facilitate deeper plant rooting and uptake of previously inaccessible subsoil N, and thereby promote plant productivity in arctic ecosystems. We conclude that changes in microbial decomposer activity, microbial N utilization and plant root density with soil depth interactively control N availability for plants in the Arctic.

Item Type:
Journal Article
Journal or Publication Title:
Environmental Research Letters
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/2100/2105
Subjects:
ID Code:
124061
Deposited By:
Deposited On:
15 Mar 2018 10:26
Refereed?:
Yes
Published?:
Published
Last Modified:
01 Jul 2020 04:23