Spatiotemporal variability in soil sulfur storage is changed by exotic Spartina alterniflora in the Jiuduansha Wetland, China

With an aim to determine whether Spartina alterniflora actively changes the habitat environment, thus facilitating its successful competition over native species, a field experiment was carried out at the Jiuduansha Wetland National Nature Reserve. Sulfur concentrations in the soil sediments were compared among wetlands dominated by the exotic Spartina alterniflora, the co-occurring native species S. mariqueter and unvegetated mudflat. The results show that the soil sulfur concentrations in the Spartina alterniflora community showed significant spatiotemporal variability with the years since invasion. The S. alterniflora community contained the highest concentrations of sulfur in the soil sediment. Moreover, the sulfur concentrations were higher in the initial invasion area than at the edges of the invading area. The was little difference in soil sulfur concentrations between communities containing native species S. mariqueter and unvegetated mudflat. There were significant correlations between soil sulfur concentrations and carbon and nitrogen concentrations; the soil nitrogen concentrations were negatively correlated with the sulfur concentrations, and the carbon concentrations were positively correlated with the sulfur concentrations. In different seasons, the concentration of sulfur is relatively higher in spring than which in other seasons. Furthermore, the sulfur concentrations at different soil depths also exhibited significant changes with depths. In addition, the soil sulfur concentrations associated with S. alterniflora also showed a trend of increasing first and then decreasing with depth, the soil sulfur concentrations in S. alterniflora soils were obviously higher than those in the S. mariqueter community and unvegetated mudflat, the maximum concentrations in S. alterniflora soils occurred at the depth of 40-60 cm. The findings of this study indicate that S. alterniflora increases wetland sulfur storage, which may explain the mechanism of expansion of S. alterniflora in the Jiuduansha Wetland.