Effect of Spartina alterniflora invasion and its controlling technologies on soil microbial respiration of a tidal wetland in Chongming Dongtan, China

The exotic species Spartina alterniflora has recently rapidly expanded in the Chongming Dongtan Nature Reserve. As a result, many technologies to control this organism have been developed. To clarify the effects of S. alterniflora invasion as well as the controlling technologies on the organic carbon reservation capability of the Chongming Dongtan Wetland, variations in soil microbial respiration (SMR) after S. alterniflora invasion and the implementation of different controlling technologies in Chongming Dongtan were analyzed, and their influencing mechanisms were studied by analyzing the soil and plant litter characteristics. The results showed that the SMR of S. alterniflora rhizosphere was 1.87 times (P = 0.000 < 0.05) higher than that of the Phragmites communis rhizosphere, but that their annual organic matter input was almost identical. These findings implied that the organic carbon reservation capability of the S. alterniflora wetland was lower than that of the native P. communis wetland. S. alterniflora stalks more easily decayed into soil than P. communis stalks due to their lower lignin content and C/N ratio. This resulted in increased soil organic carbon (SOC) and TN content in soil of the S. alterniflora rhizosphere, which likely promoted microbial activities, thereby accelerating SMR and organic carbon output. In addition, three artificial measures for controlling the spread of S. alterniflora were found to generally improve the soil microbial activities, thereby increasing organic carbon output when compared to the control. However, when compared to other measures, the effects of mowing plus tillage and waterlogging (MTW) on soil microbial activities and SMR were relatively low owing to restriction by waterlogging. Overall, MTW was a relatively low carbon method for control of the spread of S. alterniflora.