Differences in hydrophyte life forms induce spatial heterogeneity of CH4 production and its carbon isotopic signature in a temperate bog peatland. Issue 7 (14th July 2015)

• Record Type: Journal Article
• Authors: Itoh, Masayuki; Shimamura, Tetsuya; Ohte, Nobuhito; Takemon, Yasuhiro
• Is Part Of: Journal of geophysical research. Volume 120:Issue 7(2015:Sep.)
• Page Start: 1177
• Page End: 1195
• Publication Date: 2015-07-14
• Subjects: Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1002/2014JG002881
• Languages: English
• ISSNs: 2169-8953

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>To clarify the effect of differences in hydrophyte life forms on methane (CH<sub>4</sub>) production and its carbon stable isotopic signature (<italic>δ</italic><sup>13</sup>C‐CH<sub>4</sub>), we analyzed CH<sub>4</sub> and carbon dioxide (CO<sub>2</sub>) concentrations, their stable carbon isotope values, and chemical constituents dissolved in pore water 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<sub>4</sub> and CO<sub>2</sub> dissolved in pore water. Between the habitats of two <italic>Sphagnum</italic> species, DO was considerably higher, and CH<sub>4</sub> concentrations were significantly lower in <italic>Sphagnum cuspidatum</italic> Ehrh. habitats in hollow (DO: 0.62 ± 0.20 mg/L (standard error (SE)) and CH<sub>4</sub>: 0.18 ± 0.02 mmol/L) than in <italic>Sphagnum palustre</italic> L. habitats in hummock (DO: 0.29 ± 0.08 and CH<sub>4</sub>: 0.82 ± 0.06) in pore water (10 cm depth). Both DO and CH<sub>4</sub> concentrations in three vascular plant habitats (<italic>Rhynchospora fauriei</italic> Franch., <italic>Phragmites australis</italic> [reed], and <italic>Menyanthes trifoliata</italic> L.) in pore water (10 cm depth) were intermediate relative to the two <italic>Sphagnum</italic> species. However, CH<sub>4</sub> flux in <italic>M. trifoliata</italic> site was significantly higher than that at both <italic>Sphagnum</italic> sites, suggesting that the type of gas transport (diffusive or convective via root and stem) affected the depth profile of CH<sub>4</sub> concentrations and its flux. <italic>δ</italic><sup>13</sup>C‐CH<sub>4</sub> values in pore water also varied among the vegetation types, even within <italic>Sphagnum</italic> species (e.g., at 10 cm depth, <italic>δ</italic><sup>13</sup>C‐CH<sub>4</sub>: <italic>R. fauriei</italic>, −55.3 ± 1.8‰ (SE); <italic>P. australis</italic>, −57.5 ± 1.6‰; <italic>M. trifoliata</italic>, −56.7 ± 1.5‰; <italic>S. cuspidatum</italic>, −71.2 ± 1.4‰; and <italic>S. palustre</italic>, −60.4 ± 0.6‰). Our results suggest that significant differences arise in CH<sub>4</sub> concentration and <italic>δ</italic><sup>13</sup>C‐CH<sub>4</sub> values among the hydrophyte habitats even within a small peat bog and that change in vegetation relative to trophic conditions can affect CH<sub>4</sub> emissions and associated <italic>δ</italic><sup>13</sup>C‐CH<sub>4</sub> values.</p> </abstract>