Nitrogen transport in a tundra landscape: the effects of early and late growing season lateral N inputs on arctic soil and plant N pools and N2O fluxes

Laura H. Rasmussen*, Wenxin Zhang, Per Ambus, Anders Michelsen, Per Erik Jansson, Barbara Kitzler, Bo Elberling

*Corresponding author for this work

Research output: Contribution to journalJournal articleResearchpeer-review

12 Citations (Scopus)
17 Downloads (Pure)

Abstract

Understanding N budgets of tundra ecosystems is crucial for projecting future changes in plant community composition, greenhouse gas balances and soil N stocks. Winter warming can lead to higher tundra winter nitrogen (N) mineralization rates, while summer warming may increase both growing season N mineralization and plant N demand. The undulating tundra landscape is inter-connected through water and solute movement on top of and within near-surface soil, but the importance of lateral N fluxes for tundra N budgets is not well known. We studied the size of lateral N fluxes and the fate of lateral N input in the snowmelt period with a shallow thaw layer, and in the late growing season with a deeper thaw layer. We used 15N to trace inorganic lateral N movement in a Low-arctic mesic tundra heath slope in West Greenland and to quantify the fate of N in the receiving area. We found that half of the early-season lateral N input was retained by the receiving ecosystem, whereas half was transported downslope. Plants appear as poor utilizers of early-season N, indicating that higher winter N mineralization may influence plant growth and carbon (C) sequestration less than expected. Still, evergreen plants were better at utilizing early-season N, highlighting how changes in N availability may impact plant community composition. In contrast, later growing season lateral N input was deeper and offered an advantage to deeper-rooted deciduous plants. The measurements suggest that N input driven by future warming at the study site will have no significant impact on the overall N2O emissions. Our work underlines how tundra ecosystem N allocation, C budgets and plant community composition vary in their response to lateral N inputs, which may help us understand future responses in a warmer Arctic.

Original languageEnglish
JournalBiogeochemistry
Volume157
Pages (from-to)69–84
Number of pages16
ISSN0168-2563
DOIs
Publication statusPublished - 2021

Bibliographical note

CENPERM[2021]

Funding Information:
We gratefully acknowledge the financial support from the Danish National Research Foundation (CENPERM DNRF100).

Funding Information:
We gratefully acknowledge the financial support from the Danish National Research Foundation (CENPERM DNRF100). We thank Arctic Station for collaboration and logistics in performing fieldwork, E. Kolstad for NO measurements in 2018, W. Xu, B. Danielsen and A. Lambæk for help in the field in 2019, S. Ludvigsen, M. Wahlgren and G. Sylvester and E. V. Nielsen for help with lab analyses. M. Nilsson was invaluable for sample preparation. K. Rousk kindly helped with knowledge and advice. We thank the three anonymous reviewers and the handling editor for constructive and useful comments, which improved the manuscript markedly. 2

Publisher Copyright:
© 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.

Keywords

  • Arctic tundra
  • Climate change
  • Nitrate
  • Solute transport
  • Winter N mineralization

Cite this