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

• Published in: Polar Biology
• Main Authors: Barthelemy, Hélène, Nobel, Liv Alexa, Stark, Sari, Väisänen, Maria, Olofsson, Johan, Michelsen, Anders
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2024
• Subjects: maaperä; typen kierto; arctic tundra; ecosystem N retention; microbial N immobilization; 15N labelling; plant nitrogen uptake; urine; /dk/atira/pure/person/fieldofscience2010/1/18/1; name=Ecology; evolutionary biology; Arctic; Greenland; Polar Biology; Tundra
• Online Access: https://research.ulapland.fi/fi/publications/b8004bfb-2408-47a8-9517-5ace4f866178; https://doi.org/10.1007/s00300-023-03209-6; http://www.scopus.com/inward/record.url?scp=85176346000&partnerID=8YFLogxK; http://www.scopus.com/inward/citedby.url?scp=85176346000&partnerID=8YFLogxK; https://link.springer.com/article/10.1007/s00300-023-03209-6#rightslink

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 15 N-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 15 Nenrichment 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 15 N-urea. The 15 N 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 15 N recovery in soil microbial biomass was minimal, but as much as 30% of added 15 N 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.