Abiotic Factors Governing the Establishment and Expansion of Two Salt Marsh Plants in the Yangtze Estuary, China

The survival and establishment of salt marsh plant species is mainly driven by abiotic parameters. These factors can also significantly affect the outcome of competitive interactions between plant species. In this study we identify the effect of abiotic factors such as waves, currents, and sediment properties on plant establishment and development in the pioneer zone at Chongming Island, Yangtze estuary. Different propagules (seedlings, rhizome fragments, complete tussocks) of the species Spartina alterniflora and Scirpus mariqueter were planted at sites differing in current velocity, wave height, and sediment composition. Survival was strongly size-dependent, with very few of the smallest stage (seedlings) surviving. Survival of the native species S. mariqueter was higher than that of the invasive species S. alterniflora. Survival and lateral expansion rate of the experimental plants was highest at the site with lowest tidal currents, and lowest at a strongly wave-dominated site. We suggest that competitive interactions between the species are governed by plant-abiotic interactions influenced by both plant morphology and growth rate. Further we discuss the implications of these findings on the large-scale patterns of vegetation at this salt marsh.