Effects of plant invasion along a Spartina alterniflora chronosequence on organic carbon dynamics in coastal wetland in north Jiangsu.
Spartina alterniflora, an invasive grass, had rapidly replaced native plant Suaeda salsa since its intentional introduction to the coastal wetlands in Eastern China. Impacts of plant invasion along a Spartina alterniflora chronosequence on soil organic carbon (SOC) dynamics were investigated. The concentrations of SOC in bulk soil increased 70% from 2.89 g/kg soil in remnant Suaeda salsa-vegetated soil to 4.90 g/kg in 14-year Spartina alterniflora soil, and these values enhanced significantly along its chronosequence. The increase mainly resulted from a high quantity of organic residues incorporated in the soil. Compared with Suaeda salsa-vegetated soil, The SOC concentration increased significantly in coarse fraction (>250 µm and 53-250 µm) of Spartina alterniflora-vegetated soil, while there was no obvious difference in fine fraction (2-53 µm). The δ13C values of SOC for either bulk soil or particle-size fractions were evidently higher in Spartina alterniflora-vegetated soil than in Suaeda salsa-vegetated soil. There was Spartina alterniflora-derived C in all particle-size fraction, however 31%-43% of the Spartina alterniflora-derived C distributed in the coarse fraction (>250 µm). It was concluded in this study that Spartina alterniflora invasion significantly promoted SOC accumulation of surface soil in coastal wetland, and new C accumulation profoundly resulted in increasing SOC concentration of the coarse fraction (>250 µm).