DOI: 10.1007/s10533-015-0168-2
Scopus记录号: 2-s2.0-84958658083
论文题名: Modeling CH4 and CO2 cycling using porewater stable isotopes in a thermokarst bog in Interior Alaska: results from three conceptual reaction networks
作者: Neumann R.B. ; Blazewicz S.J. ; Conaway C.H. ; Turetsky M.R. ; Waldrop M.P.
刊名: Biogeochemistry
ISSN: 0168-2563
EISSN: 1573-515X
出版年: 2016
卷: 127, 期: 1 起始页码: 57
结束页码: 87
语种: 英语
英文关键词: 13CH4
; 13CO2
; Carbon fluxes
; Carbon isotopes
; Homoacetogenesis
; Methanogenesis
; Methanotrophy
; Microbial rates
; Model
; Peat
Scopus关键词: biotransformation
; carbon emission
; carbon flux
; carbon isotope
; carbon monoxide
; climate change
; in situ measurement
; methane
; methanogenesis
; methanogenic bacterium
; methanotrophy
; microbial activity
; peatland
; permafrost
; porewater
; stable isotope
; temporal variation
; thawing
; thermokarst
; wetland
; Alaska
; United States
; Carex
英文摘要: Quantifying rates of microbial carbon transformation in peatlands is essential for gaining mechanistic understanding of the factors that influence methane emissions from these systems, and for predicting how emissions will respond to climate change and other disturbances. In this study, we used porewater stable isotopes collected from both the edge and center of a thermokarst bog in Interior Alaska to estimate in situ microbial reaction rates. We expected that near the edge of the thaw feature, actively thawing permafrost and greater abundance of sedges would increase carbon, oxygen and nutrient availability, enabling faster microbial rates relative to the center of the thaw feature. We developed three different conceptual reaction networks that explained the temporal change in porewater CO2, CH4, δ13C–CO2 and δ13C–CH4. All three reaction-network models included methane production, methane oxidation and CO2 production, and two of the models included homoacetogenesis—a reaction not previously included in isotope-based porewater models. All three models fit the data equally well, but rates resulting from the models differed. Most notably, inclusion of homoacetogenesis altered the modeled pathways of methane production when the reaction was directly coupled to methanogenesis, and it decreased gross methane production rates by up to a factor of five when it remained decoupled from methanogenesis. The ability of all three conceptual reaction networks to successfully match the measured data indicate that this technique for estimating in situ reaction rates requires other data and information from the site to confirm the considered set of microbial reactions. Despite these differences, all models indicated that, as expected, rates were greater at the edge than in the center of the thaw bog, that rates at the edge increased more during the growing season than did rates in the center, and that the ratio of acetoclastic to hydrogenotrophic methanogenesis was greater at the edge than in the center. In both locations, modeled rates (excluding methane oxidation) increased with depth. A puzzling outcome from the effort was that none of the models could fit the porewater dataset without generating “fugitive” carbon (i.e., methane or acetate generated by the models but not detected at the field site), indicating that either our conceptualization of the reactions occurring at the site remains incomplete or our site measurements are missing important carbon transformations and/or carbon fluxes. This model–data discrepancy will motivate and inform future research efforts focused on improving our understanding of carbon cycling in permafrost wetlands. © 2015, Springer International Publishing Switzerland. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/83437
Appears in Collections: 气候减缓与适应 气候变化事实与影响
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作者单位: Department of Civil and Environmental Engineering, University of Washington, Seattle, WA, United States; U.S. Geological Survey, Menlo Park, CA, United States; Department of Integrative Biology, University of Guelph, Ontario, Canada; Lawrence Livermore National Laboratory, Livermore, CA, United States
Recommended Citation:
Neumann R.B.,Blazewicz S.J.,Conaway C.H.,et al. Modeling CH4 and CO2 cycling using porewater stable isotopes in a thermokarst bog in Interior Alaska: results from three conceptual reaction networks[J]. Biogeochemistry,2016-01-01,127(1)