Publikationsdatum:
2015-06-05
Beschreibung:
To clarify the effect of differences in hydrophyte life forms on methane (CH 4 ) production and its carbon stable isotopic signature (δ 13 C-CH 4 ), we analyzed CH 4 and carbon dioxide (CO 2 ) concentrations, their stable carbon isotope values, and chemical constituents dissolved in porewater in a small floating peat bog in Japan. Because eutrophication has modified the surrounding water quality the bog vegetation on the mat has been, in part, replaced by fen-type vegetation. We hypothesized that differences in hydrophyte habitats affect redox conditions, including dissolved oxygen (DO) in water and therefore the amounts and carbon isotopic values of CH 4 and CO 2 dissolved in porewater. Between the habitats of two Sphagnum species, DO was considerably higher and CH 4 concentrations were significantly lower in Sphagnum cuspidatum Ehrh. habitats in hollow (DO; 0.62 ± 0.20 mg/L (SE) and CH 4 ; 0.18 ± 0.02 mmol/L) than in Sphagnum palustre L. habitats in hummock (DO; 0.29 ±0.08 and CH 4 ; 0.82 ±0.06) in porewater (10 cm depth). Both DO and CH 4 concentrations in three vascular plant habitats ( Rhynchospora fauriei Franch., Phragmites australis [reed], and Menyanthes trifoliata L.) in porewater (10 cm depth) were intermediate relative to the two Sphagnum species. However, CH 4 flux in M. trifoliata site was significantly higher than that at both Sphagnum sites, suggesting that the type of gas transport (diffusive or convective via root and stem) affected the depth profile of CH 4 concentrations and its flux. δ 13 C-CH 4 values in porewater also varied among the vegetation types, even within Sphagnum species (e.g., at 10-cm depth, δ 13 C-CH 4 : R. fauriei , −55.3 ± 1.8‰ [SE]; P. australis , −57.5 ± 1.6‰; M. trifoliata , −56.7 ± 1.5‰; S. cuspidatum , −71.2 ± 1.4‰; and S. palustre , −60.4 ± 0.6‰). Our results suggests that significant differences arise in CH 4 concentration and δ 13 C-CH 4 values among the hydrophyte habitats even within a small peat bog and that change in vegetation relative to trophic conditions can affect CH 4 emissions and associated δ 13 C-CH 4 values.
Print ISSN:
0148-0227
Thema:
Biologie
,
Geologie und Paläontologie
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