It acts as a source of methanogenic substrate by releasing exudates and providing plant litter fall (Tong et al., 2012). Exotic Sonneratia forest and Spartina marsh both had much higher contents of TOC, TKN and TP than native wetlands, which could accelerate the production of CH4 in these systems. Secondly, plants with well-developed aerenchyma system provide a direct conduit for