Data from: Urine is an important nitrogen source for plants irrespective of vegetation composition in an Arctic tundra: insights from a 15N-enriched urea tracer experiment

• Main Authors: Barthelemy, Hélène, Stark, Sari, Michelsen, Anders, Olofsson, Johan
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: 2017
• Subjects: Above-belowground linkages; Arctic tundra; Cryptogams; Grazing intensity; Microbial N biomass; 15 N labelling; Nutrient cycling; Plant-herbivore interactions; Plant nutrient uptake; Urine; Arctic; Tundra
• Online Access: http://hdl.handle.net/10255/dryad.147131; https://doi.org/10.5061/dryad.52qh9

1. Mammalian herbivores can strongly influence nitrogen (N) cycling and herbivore urine could be a central component of the N cycle in grazed ecosystems. Despite its potential role for ecosystem productivity and functioning, the fate of N derived from urine has rarely been investigated in grazed ecosystems. 2. This study explored the fate of 15 N-enriched urea in tundra sites that have been either lightly or intensively grazed by reindeer for more than 50 years. We followed the fate of the 15 N applied to the plant canopy, at 2 weeks and 1 year after tracer addition, in the different ecosystem N pools. 3. 15 N-urea was rapidly incorporated in cryptogams and in aboveground parts of vascular plants, while the soil microbial pool and plant roots sequestered only a marginal proportion. Further, the litter layer constituted a large sink for the 15 N-urea, at least in the short term, indicating a high biological activity in the litter layer and high immobilization in the first phases of organic matter decomposition. 4. Mosses and lichens still constituted the largest sink for the 15 N-urea 1 year after tracer addition at both levels of grazing intensity demonstrating their large ability to capture and retain N from urine. Despite large fundamental differences in their traits, deciduous and evergreen shrubs were just as efficient as graminoids in taking up the 15 N-urea. The total recovery of 15 N-urea was lower in the intensively grazed sites, suggesting that reindeer reduce ecosystem N retention. 5. Synthesis The rapid incorporation of the applied 15 N-urea indicates that arctic plants can take advantage of a pulse of incoming N from urine. In addition, δ 15 N values of all taxa in the heavily grazed sites converged towards the δ 15 N values for urine, bringing further evidence that urine is an important N source for plants in grazed tundra ecosystems.