| Abstract Detail
Bryology and Lichenology Vitt, Dale [1], Graham, Jeremy [1]. The responses of Sphagnum fuscum to a gradient of increasing atmospheric nitrogen: Results of a 5-year study. Bogs, with a ground layer dominated by Sphagnum fuscum in boreal regions, have long been considered as acidic, nitrogen-limited ecosystems. The ground layer of Sphagnum mosses forms a dominant component of the developing peat column, and the production/decomposition dynamics of this layer are critical to future peat formation, and thus carbon sequestration. These production/decomposition dynamics are strongly influenced by variation in annual climate, wildfire regime, and levels of atmospheric deposition of nutrients, which are increasing across large areas of the boreal region. Here we address responses of S. fuscum to experimental five-year nitrogen additions. We added N at 5 to 25 kg ha-1 rates each growing season over the past five years and sampled the responses of S. fuscum in terms of growth, production (NPP), N-assimilation, decomposition, and abundance in a bog in NE Alberta, Canada. We conclude that 1) the annual nitrogen budget of S. fuscum is about 10 times higher than can be accounted for in background levels of N; 2) annual primary production is related to annual variation in climate; 3) NPP remains relatively constant at low levels of deposition, but decreases over time at higher levels; and 4) this decrease in NPP is not related to linear growth, but rather a decrease in population density, which reduces stem bulk density. At higher levels of deposition, S. fuscum is unable to utilize all of the deposited N as a result of diminishing populations, which results in increased vascular plant NPP and abundance. Further decline of S. fuscum nitrogen assimilation may create a positive feedback loop on N availability to vascular plant production, ultimately creating more vascular plant litter. Decompositional differences between S. fuscum and vascular plant litter may influence future inputs to the peat column resulting in less deposition of organic matter.
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1 - Southern Illinois University, Department of Plant Biology, Carbondale, IL, 62901, USA
Keywords:
Sphagnum
nitrogen assimilation
peatland
boreal
climate
net primary production.
Presentation Type: Oral Paper
Session: 8, Bryology and Lichenology (ABLS) I
Location: 205/Savannah International Trade and Convention Center
Date: Monday, August 1st, 2016
Time: 11:30 AM
Number: 8010
Abstract ID:277
Candidate for Awards:None |
