Short- and long-term plant and microbial uptake of 15N-labelled urea in a mesic tundra heath, West Greenland

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  • Hélène Barthelemy
  • Liv Alexa Nobel
  • Sari Stark
  • Maria Väisänen
  • Johan Olofsson
  • Michelsen, Anders

Terrestrial animals are key elements in the cycling of elements in the Arctic where nutrient availability is low. Waste production by herbivores, in particular urine deposition, has a crucial role for nitrogen (N) recycling, still, it remains largely unexplored. Also, experimental evidence is biased toward short-term studies and Arctic regions under high herbivore pressure. In this study, we aimed to examine the fate of N derived from urine in a nutrient poor tundra heath in West Greenland, with historical low level of herbivory. We performed a pulse labelling with 15N-urea over the plant canopy and explored ecosystem N partition and retention in the short-term (2 weeks and 1 year) and longer-term (5 years). We found that all vascular plants, irrespective of their traits, could rapidly take up N-urea, but mosses and lichens were even more efficient. Total 15N enrichment was severely reduced for all plants 5 years after tracer addition, with the exception of cryptogams, indicating that non-vascular plants constituted a long-term sink of 15N-urea. The 15N recovery was also high in the litter suggesting high N immobilization in this layer, potentially delaying the nutrients from urine entering the soil compartment. Long-term 15N recovery in soil microbial biomass was minimal, but as much as 30% of added 15N remained in the non-microbial fraction after 5 years. Our results demonstrate that tundra plants that have evolved under low herbivory pressure are well adapted to quickly take advantage of labile urea, with urine having only a transient effect on soil nutrient availability.

Original languageEnglish
JournalPolar Biology
Volume47
Pages (from-to)1-15
Number of pages15
ISSN0722-4060
DOIs
Publication statusPublished - 2024

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© 2023, The Author(s).

    Research areas

  • N labelling, Arctic tundra, Ecosystem N retention, Microbial N immobilization, Plant nitrogen uptake, Urine

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