Amino acid production exceeds plant nitrogen demand in Siberian tundra

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 ^15 N...

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Bibliographic Details
Published in:Environmental Research Letters
Main Authors: Birgit Wild, Ricardo J Eloy Alves, Jiři Bárta, Petr Čapek, Norman Gentsch, Georg Guggenberger, Gustaf Hugelius, Anna Knoltsch, Peter Kuhry, Nikolay Lashchinskiy, Robert Mikutta, Juri Palmtag, Judith Prommer, Jörg Schnecker, Olga Shibistova, Mounir Takriti, Tim Urich, Andreas Richter
Format: Article in Journal/Newspaper
Language:English
Published: IOP Publishing 2018
Subjects:
permafrost
tundra
protein depolymerization
nitrogen mineralization
nitrogen limitation
plant productivity
Environmental technology. Sanitary engineering
TD1-1066
Environmental sciences
GE1-350
Science
Q
Physics
QC1-999
Arctic
Tundra
Online Access:https://doi.org/10.1088/1748-9326/aaa4fa
https://doaj.org/article/2c32c65ac4e44c868e67706ce0cc119e
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Summary: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 ^15 N 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.

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