Abstract: In order to characterize the decomposition patterns of total organic carbon (TOC), recalcitrant organic carbon (RC) and labile organic carbon (LC) in Spartina alterniflora litter, we buried litterbags at S. alterniflora salt marshes of 3-year-old (SAF2011), 5-year-old (SAF2009), 11-year-old (SAF2003), 25-year-old (SAF1989) and S. alterniflora-Suaeda salsa salt marsh (SAF-SS) along the Xinyanggang coastal wetland in Yancheng, the largest S. alterniflora salt marsh in China. The results showed that: (1) During the oneyear decomposition, the TOC remaining percentage, RC remaining percentage and LC remaining percentage decreased monthly. The RC remaining percentage was higher than the LC remaining percentage, and the remaining percentages of TOC, RC and LC increased with the developmental duration of salt marsh. (2) The organic carbon decomposition rates differed seasonally. The higher decomposition rates of TOC, RC and LC occurred in August, January and June respectively, whereas the lower decomposition rates of TOC and LC occurred in October and February respectively, and the lower decomposition rates of RC were observed in December and February. The decomposition rate of LC was higher than that of RC, while the TOC and LC decomposition rates decreased with the developmental duration of salt marsh. The RC decomposition rates were higher in SAF2011 than in the other salt marshes. (3) After litter decomposition, the ratio of RC to TOC increased, while the ratio of LC to TOC decreased. (4) The annual TOC decomposition rates were 0.3167, 0.2632, 0.2608, 0.2583 and 0.2380 g·g^-1 for SAF1989, SAF2003, SAF2009, SAF2011 and SAFSS, respectively. These findings suggest that the development duration of salt marsh can affect decomposition processes of organic carbon in litter.

Key words: regeneration type, micro-topographic unit, reproduction mode, ecological species group., relict plant