Spartina alterniflora invasion pace in an introduced coastal wetland of China explored by 13C abundance of sediments

Background/Question/Methods

Spartina alterniflora emerged in Chinese coastline involving 11 provinces but seriously invaded tidal wetlands in Jiangsu, Shanghai, Zhejiang, and Fujian provinces. Numerous studies have been done to understand ecological impacts on S. alterniflora invasion. However, the invasion pace of S. alterniflora has not been discovered yet. As the first intentively introduced province, Fujian province has S. alterniflora over 4,000 hm² and provides a right place to picture S. alterniflora invasion pace.

Since S. alterniflora is a C4 plant which has a high efficiency of photosynthesis and significantly higher ¹³C (averagely -14‰) abundance than the C3 plant (-27‰), we used organic carbon-13 abundance in invaded sediments to trace the S. alterniflora invasion pace in Fujian. Three invaded bays, two were intentively introduced and one was unknown, were investigated for surface sediments (8-9 points each with triplicates along the bay tidal wetlands), sediment columns (three 30-cm columns each bay), and plants during the growing season.

Results/Conclusions

S. alterniflora from the investigated bays had δ¹³C abundances ranging from -14.12 to -13.23 ‰. It confirmed S. alterniflora is a C4 plant and enriched with ¹³C. However, surface sediments from two intentively introduced bays had significantly higher δ¹³C abundances than from the unknown bay (p<0.05, n=26). The profiles of δ¹³C abundance in sediment columns agreed the trend of surface sediments. The correlation analysis indicated that δ¹³C abundance was significantly correlated with total sulfur (0.424) and total phosphorus (-0.426) (p<0.05, n=26). This result was coincided with physiological characteristics of S. alterniflora, i.e. sulfur enrichment and high phosphorus demand. It also confirmed that ¹³C in surface sediment was mainly derived from S. alterniflora plantation. In short, the δ¹³C abundance indicated the intentively introduced bays had a longer duration of S. alterniflora invasion than the unknown bay, which might be invaded by seeds from the two intentively introduced bays via inshore current and tide.