Division of labor in rhizomatous species: Comparative performance of native and invasive species in the tidal marshes of the Yangtze River estuary, China

We compared reproductive characteristics of Scirpus mariqueter and Spartina alterniflora in monocultures and mixed communities to assess the importance of clonality in the population distribution and colonization of the two species. In the core S. alterniflora zone, individuals were taller and there were fewer underground tillers than in the Spartina-Scirpus zone. Every sexual S. alterniflora individual produced about two underground tillers in the S. alterniflora zone, which was two thirds as many as in the Spartina-Scirpus zone. In contrast, the height of sexual S. mariqueter was the highest in the mixed zone, whereas the numbers of flowering individuals and vegetative individuals were the highest in the core and the Scirpus-tidal flat zones, respectively. In the Scirpus-tidal flat zone each sexual individual produced 14 vegetative individuals, which was 23 times that produced in the mixed zone, and 45 times that in the core zone. Aboveground biomass and density of sexual individuals decreased from the core to the Scirpus-tidal flat zone. The ratio of aboveground to belowground biomass was lower in core zones of the two species than in their mixed zones. From the S. alterniflora to the tidal flat zone there was a decrease in salinity and redox potential and an increase in soil moisture.