Abstract
Nitrogen availability in the Arctic strongly influences plant productivity and distribution, and in permafrost systems with patterned ground, ecosystem carbon and nutrient cycling can vary substantially over short distances. Improved understanding of fine-scale spatial and temporal variation in soil N availability is needed to better predict tundra responses to a warming climate. We quantified plant-available inorganic nitrogen at multiple soil depths in 12 microhabitats associated with a gradient from low-center ice-wedge polygons to high-center polygons in coastal tundra at Utqiaġvik (formerly Barrow), Alaska. We measured vegetation composition, biomass, N content, and rooting depth distribution, as well as soil temperature, moisture, pH, and thaw depth to determine relationships between the spatial and temporal variability in N availability and environmental and vegetation drivers. Soil moisture varied across the microhabitats of the polygonal terrain and was the most important variable linked to distribution of both ammonium and nitrate, with ammonium predominating in wetter areas and nitrate predominating in drier areas. Total inorganic N availability increased as the soil in the active layer thawed, but the newly available N near the permafrost boundary late in the season was apparently not available to roots and did not contribute to plant N content. Nitrate in the drier sites also was not associated with plant N content, raising the possibility of N losses from this N-limited ecosystem. The strong relationship between soil moisture, inorganic N availability, and plant N content implies that understanding hydrological changes that may occur in a warming climate is key to determining nutrient cycling responses in complex polygonal tundra landscapes.
| Original language | English |
|---|---|
| Pages (from-to) | 528-543 |
| Number of pages | 16 |
| Journal | Ecosystems |
| Volume | 22 |
| Issue number | 3 |
| DOIs | |
| State | Published - Apr 15 2019 |
Funding
Received 27 March 2018; accepted 13 July 2018; published online 3 August 2018 Electronic supplementary material: The online version of this article (https://doi.org/10.1007/s10021-018-0285-6) contains supplementary material, which is available to authorized users. Author Contributions RJN, VLS, and CMI conceived and designed the study. RJN, VLS, CMI, and JC performed field research and laboratory analyses. RJN and VLS analyzed the data and wrote the paper with substantial input from CMI. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the US Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/down loads/doe-public-access-plan). *Corresponding author; e-mail: [email protected] We thank Deanne Brice, Ingrid Slette, and Kelsey Carter for their help in the field and laboratory, and Verity Salmon and two anonymous reviewers for their helpful comments on an earlier version of this paper. The Next-Generation Ecosystem Experiments (NGEE Arctic) project is supported by the US Department of Energy, Office of Science, Biological and Environmental Research Program. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the US Department of Energy under contract DE-AC05-00OR22725.
Keywords
- Arctic
- active layer
- ammonium
- ice-wedge polygons
- microhabitat
- nitrate
- plant-available nitrogen
- root distribution
- thaw
- tundra