The spatial overlapping regulated by nitrogen promotes the Spartina alterniflora potential regenerated invasion in coastal wetlands

Abstract The mechanisms that link the aboveground plant community structure with soil seed bank is crucial for predicting the potential regeneration direction. However, the spatial structure of invasive clonal plants should be reasonably quantified. We assume that the selection effect of Spartina alterniflora community spatial structure on soil seed bank composition would affect the seed reproduction invasion intensity. We set the native species of Phragmites australis in Dongtan wetland as a reference object, to explore the nitrogen regulation on the soil seed bank formation processes after S. alterniflora became the dominant species. The results showed that the S. alterniflora growth tended to be stable in summer and autumn, and its height change trend and peak height under different coverage was relatively consistent. The seasonal variation trend of P. australis height is opposite to that of S. alterniflora. In the autumn community structure at mature stage, the dominance index of S. alterniflora and P. australis showed a downward trend from low to high aboveground coverage after the soil seed bank germination, and the dominance index of S. alterniflora was higher than that of P. australis. The overlapping resistance structure of S. alterniflora community was synergistically affected by soil ammonium nitrogen, leaf total nitrogen and soil microbial biomass nitrogen, and the effect of this structure on the soil seed bank formation under different soil depth showed an opposite trend. Our results suggest that the overlapping complementarity between S. alterniflora plays a positive regulatory role between functional trait plasticity and sexual reproduction advantage.