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Wenxin Zhang

Researcher

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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

Author

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

Summary, in English

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.

Department/s

  • Dept of Physical Geography and Ecosystem Science
  • BECC: Biodiversity and Ecosystem services in a Changing Climate
  • MERGE: ModElling the Regional and Global Earth system

Publishing year

2022

Language

English

Pages

69-84

Publication/Series

Biogeochemistry

Volume

157

Issue

1

Document type

Journal article

Publisher

Springer

Topic

  • Ecology
  • Climate Research
  • Soil Science

Keywords

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

Status

Published

ISBN/ISSN/Other

  • ISSN: 0168-2563