Characteristics of Plant Distribution in the Reclaimed Dredging Area in Gwangyang Bay, Korea

In order to elucidate the mechanisms affecting plant distributions in the reclaimed dredging area in the Gwangyang steelworks, in the Gwangyang Bay, Korea, we examined soil characteristics and plant distributions in four study sites and a control site in the study area. Desalination occurring along a gradient with increasing elevation, resulting in decrease of soil pH, EC, P, K, Cl, Ca, Mg, and salt and an increase in soil T-N, silt, clay contents. From site 1 (the lowest-elevation site) to site 5 (the highest-elevation site), halophytes decreased in abundance and nonhalophytes increased. The dominant species in each site were: Phragmites communis, Limonium tetragonum, and 12 additional species at site 1, Carex pumila, Suaeda japonica, and 15 additional species at site 2, Spergularia marina, Scirpus planiculmis, and 22 additional species at site 3, Miscantus sinensis, Lespedeza bicolor, and 26 additional species at site 4 and Pinus thunberii, Rhododendron mucronulatum, and 39 additional species at site 5, which resembled a naturally-occurring P. thinbergii community. Cluster analysis of the vegetation data matrix grouped the 35 plots into 5 major groups, and cluster analysis using the soil environment data matrix revealed 4 major groups. CCA of the floristic and environmental data matrix showed a positive relationship of SAR, EC, Na, Cl, and Ca, which are related to salt, in the 1∨st axis and 2∨nd axis, but negative relationships for altitude, organic contents, silt, and clay contents. Notably, plant species in the reclaimed dredging area that were separated along the 1∨st axis showed strong relationships with factors that related to salt. Long-term exposure to natural rainfall in the reclaimed dredging area changed the soil characteristics, such as salinity. This change in soil characteristics might alter the SAR, which affects plant survival strategies in a given habitat. These results strongly indicated that factors related to salt and elevation play important roles in determining the overall plant distribution in the reclaimed dredging area.