Effect of Water Level Fluctuation and Nitrate Concentration on Soil-Surface CO2 and CH4 Emissions from Riparian Freshwater Marsh Wetland

This study assessed the effect of water level fluctuation and NO3-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm{NO}}_3^{-}$$\end{document} concentration levels on the soil CO2 and CH4fluxes from wetland. Intact soil columns collected from sites dominated by different vegetation types were incubated in laboratory and continuously treated with NO3-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm{NO}}_3^{-}$$\end{document} enriched water. CO2 and CH4fluxes were measured from three manipulated water levels: 5 cm above the soil water surface, −10 cm and -20 cm below the soil water surface. Two NO3-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm{NO}}_3^{-}$$\end{document} concentration levels 30 mg/L and 60 mg/L were used. This study revealed significant interaction effect between NO3-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm{NO}}_3^{-}$$\end{document} concentration and water level on CO2 and CH4 fluxes. Water level fluctuation significantly affected CO2 fluxes. The overall mean CO2 emission at 5 cm of 6.45 mg/m2/h was two and five times lower than that at −10 cm (22.52 mg/m2/h) and − 20 cm (32.50 mg/m2/h), respectively. The mean CO2 fluxes in Calamagrostis angustifolia Kom was significantly higher when high NO3-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm{NO}}_3^{-}$$\end{document} concentration was added in the soil while in Phragmites australis (Cav.) Trin. ex Steud and Carex pseudocuraica F.Schmidt higher CO2 fluxes were observed when low NO3-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm{NO}}_3^{-}$$\end{document} concentration was added. NO3-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm{NO}}_3^{-}$$\end{document} concentration levels significantly affected CH4 fluxes with the highest mean values measured when low NO3-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm{NO}}_3^{-}$$\end{document} concentration was added. This implies that there could be significant change in CO2 and CH4 fluxes as a response of water level drawdown due to wetland drainage. High NO3-\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\mathrm{NO}}_3^{-}$$\end{document} concentration leads to increase in CO2 in C. pseudo-curaica likely due to nutritional effect, and reduction in CO2 in C. pseudo-curaica and P. australis probable due to inducing carbon-limitation.