читать, читать и еще раз читать, Gorm обратите внимание


Автор сообщения: Alexei
Дата и время сообщения: 26 April 2004 at 14:49:14:

В ответ на сообщение: нерелевантный - это видимо я?

Читайте и имейте хороший день. Как говорится, полнотекстовики доступны по требованию. Особенно рекомендую, первую статью. А именно таблицу 1 из этой работы. Горм, может стоит разместить ее у Вас на сайте?

Table 1. 14C content of emitted methane collected in chambers (с незначительными сокращениями)
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Site d13C o/oo d14C o/oo
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BOGS
Fairlnd -71.9 -160.6(8.7)
Red Lake -62.3 -139.6(7.7)
Sturgeon -73.5 -135.4(6.9)
Mean of 3 bogs -145.2 +/- 13.5
FENS
Western Water Tract -63.5 -149.1(10)
Western Water Tract -65.6 -154.8(8.8)
Red Lake 4 Water Tract -69.0 -141.8(6.9)
Mean of 3 fen samples -148.6 +/- 6.5
Mean of 6 samples -146.9 +/- 9.7
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Geochimica et Cosmochimica Acta
1995
v. 59, No, 17, pp. 3663-3668.
RADIOCARBON EVIDENCE FOR THE SUBSTRATES SUPPORTING METHANE FORMATION WITHIN NORTHERN MINNESOTA PEATLANDS
J.P. Chanton, J.E. Bauer, P.A. Glaser, D.I. Siegel, C.A. Kelley, S.C. Tyler, E.H. Romanowicz, A. Lazrus
Bogs and fens from northern Minnesota produce large quantities of CH4, which may be either emitted to the atmosphere or stored in below-ground reservoirs. The identity of the organic materials that support CH4 production has been uncertain, but we present evidence that a significant fraction of surface emission and below-ground CH4 is derived from recently fixed organic compounds. First, the CH4 emitted from both bogs and fens has a 14C signature equivalent to contemporary values for atmospheric CO2. Second, in flooded fens rates of CH4 emission are linearly related to rates of CO2 exchange and to the d13C of emitted CH4. Third, peat-porewaters as deep as several meters below the surface contain mixtures of CH4 derived from both modern and older organic substrates. The source of the modern organic substrates is most likely dissolved organic compounds produced from the decay of recently produced litter, roots and root exudation products and transported into deeper layers of the peat. These data indicate that CH4 emissions are closely linked to the living vegetation and hydrology of northern peatlands and less dependent on the lability and decomposition of peat within the deeper layers of the catotelm.


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Annals of Botany 86: 655-663, 2000

Methane Concentration and Stable Isotope Distribution as Evidence of Rhizospheric Processes: Comparison of a Fen and Bog in the Glacial Lake Agassiz Peatland Complex
L. S. Chasar+, J. P. Chanton, P. H. Glaser and D. I. Siegel
Department of Oceanography, Florida State University, Tallahassee, FL 32306, USA Department of Geology and Geophysics, University of Minnesota, Minneapolis, MN 55455, USA Department of Earth Sciences, Syracuse University, Syracuse, NY 13244, USA

Received: 20 September 1999 ; Returned for revision: 21 January 2000 . Accepted: 15 March 2000

This study evaluates relationships between vegetation and stable isotope distribution within a large, northern peat-accumulating wetland. Concentration and 13C for both porewater and emitted methane were obtained from June-September for two systems characterized by different plant assemblages and hydrologic regimes: a Carex -dominated fen and a Sphagnum -dominated, forested bog crest. Average methane emissions were higher in the fen than at the bog crest across the entire growing season. Fen porewater methane concentrations were maintained at consistently low levels in the upper one-third of the peat column, and emitted methane was substantially13C-depleted (by approx. 6) relative to shallow porewater methane, trends which are characteristic of passive plant-mediated transport of rhizospheric methane to the atmosphere. Fen porewater 13C-CH4values in shallow peat (approx. -59) suggest that microbial respiration was primarily driven by acetate fermentation. CO2reduction became more important deeper in the peat column with 13C-CH4values ranging from approx. -65 to -69 between 1 and 2.8 m. In contrast to the fen, porewater methane concentrations in the bog were usually at near-maximum levels just below the water table. 13C values for emitted CH4in the bog were enriched relative to those for shallow porewater CH4by approx. 10, indicating that methane was subject to oxidation as it exited from the peat via passive diffusion. Methanogenesis in the peat at the bog crest appears to have been substrate-limited, with porewater 13C-CH4(approx. -67) suggestive of CO2reduction at all depths.Copyright 2000 Annals of Botany Company




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