Publication Date:
2022-05-25
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.
Description:
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.
Description:
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.
Keywords:
15NH4
;
Arctic tundra watershed
;
Total dissolved N
;
Downhill transport of N
;
Hydrolysable amino acids
;
Hydrolysable amino sugars
;
Mosses
;
N dynamics
;
N immobilization
;
N leaching
;
N limitation
;
Snowmelt
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Format:
application/vnd.ms-excel
Format:
application/pdf
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