Differences in hydrophyte life forms induce spatial heterogeneity of CH4 production and its carbon isotopic signature in a temperate bog peatland

作者：Itoh Masayuki^*; Shimamura Tetsuya; Ohte Nobuhito; Takemon Yasuhiro

来源：Journal of Geophysical Research-Biogeosciences, 2015, 120(7): 1177-1195.

DOI：10.1002/2014JG002881

• temperate peatland
• methane
• hydrophyte habitat
• redox condition
• carbon stable isotope
• sphagnum

To clarify the effect of differences in hydrophyte life forms on methane (CH4) production and its carbon stable isotopic signature (C-13-CH4), we analyzed CH4 and carbon dioxide (CO2) 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 CH4 and CO2 dissolved in pore water. Between the habitats of two Sphagnum species, DO was considerably higher, and CH4 concentrations were significantly lower in Sphagnum cuspidatum Ehrh. habitats in hollow (DO: 0.620.20mg/L (standard error (SE)) and CH4: 0.180.02mmol/L) than in Sphagnum palustre L. habitats in hummock (DO: 0.290.08 and CH4: 0.820.06) in pore water (10cm depth). Both DO and CH4 concentrations in three vascular plant habitats (Rhynchospora fauriei Franch., Phragmites australis [reed], and Menyanthes trifoliata L.) in pore water (10cm depth) were intermediate relative to the two Sphagnum species. However, CH4 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 CH4 concentrations and its flux. C-13-CH4 values in pore water also varied among the vegetation types, even within Sphagnum species (e.g., at 10cm depth, C-13-CH4: R. fauriei, -55.3 +/- 1.8 parts per thousand (SE); P. australis, -57.5 +/- 1.6 parts per thousand; M. trifoliata, -56.7 +/- 1.5 parts per thousand; S. cuspidatum, -71.2 +/- 1.4 parts per thousand; and S. palustre, -60.4 +/- 0.6 parts per thousand). Our results suggest that significant differences arise in CH4 concentration and C-13-CH4 values among the hydrophyte habitats even within a small peat bog and that change in vegetation relative to trophic conditions can affect CH4 emissions and associated C-13-CH4 values.

• 出版日期2015-7
• 单位防灾科技学院