Methane Transport Of Spartina Alterniflora And Cyperus Malaccensis Lam. Var. Brevifolius Bocklr.

The characteristics of plant mediated transport and emission of CH4 through Spartina alterniflora and Cyperus malaccensis Lam.var.brevifolius Bocklr. during different growth stages was studied. The results showed that the aerenchymas of both plants were well developed. The methane transport capacity of Spartina alterniflora was obviously higher than that of Cyperus malaccensis Lam.var.brevifolius Bocklr.. It was determined by the size of the plant and the cavity.The methane concentration in the medullary cavity of Spartina alterniflora was much higher than that in the atmosphere. There was an concentration gradient from bottom to up of plants. Methane released mainly from the part below the half of plant hight, especilly from the hight of 0-20cm. The release rates of the upper half part increased gradually after flowering stage, which may be related to the development of the aerenchyma.The methane transport capacity of Spartina alterniflora during different growth stages were significantly different. Differences in methane transport capacity among different growth stages were attributed to the vegetation growth state, the development of aerenchyma, air temperature and other environment factors. The methane transport capacity of fresh plant of Spartina alterniflora were larger than standing dead.The methane transport capacity after the ebb were significantly higher than before flood. In the cold day of winter, Spartina alterniflora may employ diffusive transport mode during the daytime attributed to the low temperature, but utilized convective through-flow transport during the windy night.The methane transport capacity of Cyperus malaccensis Lam.var.brevifolius Bocklr. between the daytime and night were significantly different in summer, the methane transport capacity of daytime was larger than night, indicading that Cyperus malaccensis Lam.var.brevifolius Bocklr.'s transport mode of methane were the combination of diffusive transport during the daytime and convective through-flow transport at night. In winter, Cyperus malaccensis Lam.var.brevifolius Bocklr. employed diffusive transport driven by the capacity of releasing oxygen in rhizome and rhizosphere caused by plant photosynthesis. The methane transport capacity in summer was larger than winter. The difference of methane transport capacity among different growth stages were not significant.The contribution of plant mediated transport to methane emission of wetland of Cyperus malaccensis Lam.var.brevifolius Bocklr. changed less than that of Spartina alterniflora.The average contribution rate was below 50%, and the contribution rate was largest in July, then decreased gradually.The main methane relaese part in winter of Cyperus malaccensis Lam.var.brevifolius Bocklr. was the stem, and the release proportion in different height part were similar, whiche was determined by the situation of aerenchyma.