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Title: Long-term carbon and nitrogen dynamics at SPRUCE revealed through stable isotopes in peat profiles

Peatlands encode information about past vegetation dynamics, climate, and microbial processes. Here, we used δ 15N and δ 13C patterns from 16 peat profiles to deduce how the biogeochemistry of the Marcell S1 forested bog in northern Minnesota responded to environmental and vegetation change over the past ~10 000 years. In multiple regression analyses, δ 15N and δ 13C correlated strongly with depth, plot location, C/N, %N, and each other. Correlations with %N, %C, C/N, and the other isotope accounted for 80 % of variance for δ 15N and 38 % of variance for δ 13C, reflecting N and C losses. In contrast, correlations with depth and topography (hummock or hollow) reflected peatland successional history and climate. Higher δ 15N in plots closer to uplands may reflect upland-derived DON inputs and accompanying shifts in N dynamics in the lagg drainage area surrounding the bog. The Suess effect (declining δ 13CO 2 since the Industrial Revolution) lowered δ 13C in recent surficial samples. High δ 15N from –35 to –5 cm probably indicated the depth of ectomycorrhizal activity after tree colonization of the peatland over the last 400 years, as confirmed by the occasional presence of wood down to –35 cm depth. Highmore » δ 13C at ~4000 years BP (–65 to –105 cm) could reflect a transition at that time to slower rates of peat accumulation, when 13C discrimination during peat decomposition may increase in importance. Low δ 13C and high δ 15N at –213 and –225 cm (~8500 years BP) corresponded to a warm period during a sedge-dominated rich fen stage. As a result, the above processes appear to be the primary drivers of the observed isotopic patterns, whereas there was no clear evidence for methane dynamics influencing δ 13C patterns.« less
Authors:
 [1] ;  [2] ;  [3] ;  [3] ; ORCiD logo [4] ;  [1] ;  [5]
  1. Univ. of New Hampshire, Durham, NH (United States)
  2. Univ. of New Hampshire, Durham, NH (United States); FAO/IAEA Agriculture & Biotechnology Labs., Seibersdorf (Austria)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  5. Iowa State Univ., Ames, IA (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Publication Date:
Report Number(s):
PNNL-SA-126833
Journal ID: ISSN 1726-4189; 49729; KP1704020
Grant/Contract Number:
AC05-76RL01830; AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Biogeosciences (Online)
Additional Journal Information:
Journal Name: Biogeosciences (Online); Journal Volume: 14; Journal Issue: 9; Journal ID: ISSN 1726-4189
Publisher:
European Geosciences Union
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; Environmental Molecular Sciences Laboratory; 54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1363995
Alternate Identifier(s):
OSTI ID: 1376511