The variation of methane emission from freshwater marshes and response to the exogenous N in Sanjiang Plain Northeast China: Fid-Bau Portal

The variation of methane emission from freshwater marshes and response to the exogenous N in Sanjiang Plain Northeast China

Zhang, Lihua / Song, Changchun / Wang, Dexuan / Wang, Yiyong / Xu, Xiaofeng

Abstract

AbstractThe methane emitted from freshwater marsh is the difference between the production and oxidation of ${CH}_{4}$ which reaches the atmosphere via diffusion, ebullition, or by passage through aerenchymous tissues of higher plants. To evaluate the variation of ${CH}_{4}$ emission and the effects of increased exogenous N on ${CH}_{4}$ emission, we have raised in situ the exogenous N with the rates of $0 g N m^{- 2}$ (control), $6 g N m^{- 2}$ (low nitrogen level), $12 g N m^{- 2}$ (medial nitrogen level) and $24 g N m^{- 2}$ (high nitrogen level), respectively, in Sanjiang Plain marsh ecosystem Northeast China. ${CH}_{4}$ emissions were measured using the static chamber and gas chromatogram techniques. The daily average ${CH}_{4}$ emission during the different growing stages from the marsh varies from $- 0.06$ to $13.54 mg$ ${CH}_{4} m^{- 2} h^{- 1}$ with the daily observation. The exogenous N significantly increased the mean seasonal ${CH}_{4}$ emission rate by 181% (low nitrogen level, $P < 0.01$ ), 254% (medial nitrogen level, $P < 0.01$ ) and 155% (high nitrogen level, $P < 0.01$ ), respectively. The effects of exogenous N strongly interacted with the plant aboveground biomass, which was a variable explaining most variation in ${CH}_{4}$ emission. We also find the net effect of exogenous N on ${CH}_{4}$ emission from freshwater marshes most likely depends on the counterbalance between the N-induced increases in ${CH}_{4}$ production and oxidation, as a N excess may result in the inhibition of ${CH}_{4}$ emission, and in the stimulation of ${CH}_{4}$ emission.