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Nitrogen dynamics in a small arctic watershed: retention and downhill movement of 15N

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dc.contributor.author Yano, Yuriko
dc.contributor.author Shaver, Gaius R.
dc.contributor.author Giblin, Anne E.
dc.contributor.author Rastetter, Edward B.
dc.contributor.author Nadelhoffer, Knute J.
dc.date.accessioned 2010-09-07T15:28:08Z
dc.date.available 2010-09-07T15:28:08Z
dc.date.issued 2009-06-12
dc.identifier.uri http://hdl.handle.net/1912/3903
dc.description Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Ecological Society of America for personal use, not for redistribution. The definitive version was published in Ecological Monographs 80 (2010): 331-351, doi:10.1890/08-0773.1. en_US
dc.description.abstract We examined short- and long-term nitrogen (N) dynamics and availability along an arctic hillslope in Alaska, USA, using stable isotope of nitrogen (15N), as a tracer. Tracer levels of 15NH4+ were sprayed once onto the tundra at six sites in four tundra types; heath (crest), tussock with high and low water flux (mid- and foot-slope), and wet sedge (riparian). 15N in vegetation and soil was monitored to estimate retention and loss over a 3-yr period. Nearly all 15NH4+ was immediately retained in the surface moss-detritus-plant layer and > 57 % of the 15N added remained in this layer at the end of the second year. Organic soil was the second largest 15N sink. By the end of the third growing season, the moss-detritus-plant layer and organic soil combined retained ≥ 87 % of the 15N added except at the mid-slope site with high water flux, where recovery declined to 68 %. At all sites, non-extractable and non-labile-N pools were the principal sinks for added 15N in the organic soil. Hydrology played an important role in downslope movement of dissolved 15N. Crest and mid-slope with high water flux sites were most susceptible to 15N losses via leaching perhaps because of deep permeable mineral soil (crest) and high water flow (mid-slope with high water flux). Late spring melt-season also resulted in downslope dissolved-15N losses, perhaps because of an asynchrony between N release into melt water and soil immobilization capacity. We conclude that separation of the rooting zone from the strong sink for incoming N in the moss detritus-plant layer, rapid incorporation of new N into relatively recalcitrant soil-N pools within the rooting zone, and leaching loss from the upper hillslope would all contribute to the strong N limitation of this ecosystem. An extended snow-free season and deeper depth of thaw under warmer climate may significantly alter current N dynamics in this arctic ecosystem. en_US
dc.description.sponsorship Funding was provided by NSF grant #0444592. Additional support was provided by Toolik Field Station Long Term Ecological Research program, funded by National Science Foundation, Office of Polar Programs. en_US
dc.format.mimetype application/vnd.ms-excel
dc.format.mimetype application/pdf
dc.language.iso en_US en_US
dc.relation.uri http://dx.doi.org/10.1890/08-0773.1
dc.subject 15NH4 en_US
dc.subject Arctic tundra watershed en_US
dc.subject Total dissolved N en_US
dc.subject Downhill transport of N en_US
dc.subject Hydrolysable amino acids en_US
dc.subject Hydrolysable amino sugars en_US
dc.subject Mosses en_US
dc.subject N dynamics en_US
dc.subject N immobilization en_US
dc.subject N leaching en_US
dc.subject N limitation en_US
dc.subject Snowmelt en_US
dc.title Nitrogen dynamics in a small arctic watershed: retention and downhill movement of 15N en_US
dc.type Preprint en_US


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