The fate of 15N added to high Arctic tundra to mimic increased inputs of atmospheric nitrogen released from a melting snowpack

• Published in: Global Change Biology
• Main Authors: Tye, A. M., Young, S. D., Crout, N. M. J., West, H. M., Stapleton, L. M., Poulton, P. R., Laybourn-Parry, J.
• Format: Other/Unknown Material
• Language: unknown
• Published: Wiley 2005
• Subjects: biodiversity conservation; Ecology; Environmental Sciences; Arctic; Salix polaris; Tundra; Spitsbergen
• Online Access: https://repository.rothamsted.ac.uk/item/897v9/the-fate-of-15n-added-to-high-arctic-tundra-to-mimic-increased-inputs-of-atmospheric-nitrogen-released-from-a-melting-snowpack; https://doi.org/10.1111/j.1365-2486.2005.01044.x

Increases in the long-range aerial transport of reactive N species from low to high latitudes will lead to increased accumulation in the Arctic snowpack, followed by release during the early summer thaw. We followed the release of simulated snowpack N, and its subsequent fate over three growing seasons, on two contrasting high Arctic tundra types on Spitsbergen (79 degrees N). Applications of N-15 (99 atom%) at 0.1 and 0.5 g N m(-2) were made immediately after snowmelt in 2001 as either (NaNO3)-N-15 or (NH4Cl)-N-15. These applications are approximately 1 x and 5 x the yearly atmospheric deposition rates. The vegetation at the principal experimental site was dominated by bryophytes and Salix polaris while at the second site, vegetation included bryophytes, graminoids and lichens. Audits of the applied N-15 were undertaken, over two or three growing seasons, by determining the amounts of labeled N in the soil (0-3 and 3-10 cm), soil microbial biomass and different vegetation fractions. Initial partitioning of the N-15 at the first sampling time showed that similar to 60% of the applied N-15 was recovered in soil, litter and plants, regardless of N form or application rate, indicating that rapid immobilization into organic forms had occurred at both sites. Substantial incorporation of the N-15 was found in the microbial biomass in the humus layer and in the bryophyte and lichen fractions. After initial partitioning there appeared to be little change in the total N-15 recovered over the following two or three seasons in each of the sampled fractions, indicating highly conservative N retention. The most obvious transfer of N-15, following assimilation, was from the microbial biomass into stable forms of humus, with an apparent half-life of just over 1 year. At the principal site the microbial biomass and vascular plants were found to immobilize the greatest proportion of N-15 compared with their total N concentration. In the more diverse tundra of the second site, lichen species and graminoids competed effectively ...