Mechanism of the plant community succession process in the Zhenjiang Waterfront Wetland

In this study, replacement of dominant populations (Phragmites australis and Phalaris arundinacea) in the plant community succession process in the Zhenjiang Waterfront Wetland was approached from three aspects: growth, photosynthesis, and specific competitive characteristics. The productivity of Phragmites, based on intrinsic rate of increase and environmental carrying capacity of the several chosen growth indices (plant length, sheath height, and biomass), was significantly higher than that of Phalaris. Phragmites had a higher photosynthetic rate than Phalaris. However, Phalaris had a markedly lower light compensation point, which suggested that it was capable of better utilization of weak light. This possibly might account for its survival beneath Phragmites. At three different coverage gradients, the relative yield total was greater than 1, indicating a certain degree of complementary resource utilization via niche separation between both species. Significant differences in the competition ratio of both species indicated a superiority of Phragmites over Phalaris in terms of competitive capability. Thus, the Phragmites population tended to exclude the Phalaris population and became the mono-dominant population in the community succession process. For Phalaris, traits such as its better utilization of weak light, its complementary resource utilization, and a partial separation of growth period compared to Phragmites prevented complete replacement of its population to some degree. In this particular study area in the Zhenjiang Waterfront Wetland, the hydrological conditions of the river beach determined by its elevation possibly acted as the dominant regulator of the plant succession process.