The fate of 15N added to high Arctic tundra to mimic increased inputs of atmospheric nitrogen released from a melting snowpack
Increases in the long-range aerial transport of reactive N species from low to highlatitudes will lead to increased accumulation in the Arctic snowpack, followed by releaseduring the early summer thaw. We followed the release of simulated snowpack N, and itssubsequent fate over three growing seasons...
| Published in: | Global Change Biology |
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| Main Authors: | , , , , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
Blackwell Publishing Ltd
2005
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| Subjects: | |
| Online Access: | http://interscience.wiley.com https://doi.org/10.1111/j.1365-2486.2005.01044.x http://ecite.utas.edu.au/49095 |
| Summary: | Increases in the long-range aerial transport of reactive N species from low to highlatitudes will lead to increased accumulation in the Arctic snowpack, followed by releaseduring the early summer thaw. We followed the release of simulated snowpack N, and itssubsequent fate over three growing seasons, on two contrasting high Arctic tundra typeson Spitsbergen (791N). Applications of 15N (99 atom%) at 0.1 and 0.5 gNmr2 were madeimmediately after snowmelt in 2001 as either Na15NO3 or 15NH4Cl. These applicationsare approximately 1 and 5 the yearly atmospheric deposition rates. The vegetation atthe principal experimental site was dominated by bryophytes and Salix polaris while atthe second site, vegetation included bryophytes, graminoids and lichens. Audits of theapplied 15N were undertaken, over two or three growing seasons, by determining theamounts of labeled N in the soil (0-3 and 3-10 cm), soil microbial biomass and differentvegetation fractions.Initial partitioning of the 15N at the first sampling time showed that 60% of theapplied 15N was recovered in soil, litter and plants, regardless of N form or applicationrate, indicating that rapid immobilization into organic forms had occurred at both sites.Substantial incorporation of the 15N was found in the microbial biomass in the humuslayer and in the bryophyte and lichen fractions. After initial partitioning there appearedto be little change in the total 15N recovered over the following two or three seasons ineach of the sampled fractions, indicating highly conservative N retention. The mostobvious transfer of 15N, following assimilation, was from the microbial biomass intostable forms of humus, with an apparent half-life of just over 1 year. At the principal sitethe microbial biomass and vascular plants were found to immobilize the greatestproportion of 15N compared with their total N concentration. In the more diverse tundraof the second site, lichen species and graminoids competed effectively for 15NH4-N and15NO3-N, respectively. Results suggest that Arctic ... |
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