Understanding of salt marsh plant zonation caused by abiotic and biotic factors is essential for successful conservation plans in the face of ongoing environmental change. The frequency of flooding is more important than elevation in predicting marsh plant zones. Tidal marsh plants are distributed across a wide gradient of soil-water salinities. Studies done to date indicate that redox potential, ionic composition of soil, moisture content of soil, latitude, topographical, and climatic factors may play some role in forming vegetation zones. Competition and facilitation are important in mediating zonation, and the importance of facilitation of plant growth increases with increasing physical stress within the abiotic range limits. A refined understanding of facilitation along stress gradients would help inform successful restoration and management of vegetation. In the salt marsh plant community, a trade-off between belowground competitive ability and the ability to tolerate physical stressors appears to drive plant growth patterns across the landscape. Understanding and predicting shifts between bare flats and vegetated marshes is of great importance, because it provides a useful scientific basis for understanding vegetation zonation. A bimodal distribution of intertidal elevations, positive feedbacks, and alternative stable states and abrupt shifts in elevation from bare flats to vegetated states are present in salt marsh ecosystems. Strategies to assess whether alternative stable states are present are now converging in fields as disparate as desertification, limnology, oceanography, ecology and climatology. Further research should therefore focus on the conditions for and the specific mechanisms behind alternative stable states in salt marsh ecosystems.

We studied how plant species distribution was regulated by the relationships between vegetation and soil factors on the southwestern coast of South Korea. Vegetation was classified using two-way indicator species analysis (TWINSPAN), thereby producing four vegetation groups that were linked to three habitat types. Two ordination techniques --detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA) --were applied to examine the relationships between vegetation and 12 edaphic factors, including soil pH, water and osmotic potentials, moisture content, electrical conductivity, CI and Na § contents, total Kjeldahl nitrogen, and contents of organic matter, sand, silt, and clay. Results were similar for both types of evaluations. According to DCA and CCA, the 23 communities tended to cluster into three types: salt swamp, salt marsh, and sand dune. The first two canonical axes accounted for 14.9% of the community-soil factor relationship among communities. As identified via CCA, the main gradients were soil-water relations and soil texture.

The coastal landscapes in southwestern Korea include a diverse array of tidal wetlands and salt marshes. These coastal zones link the ecological functions of marine tidal wetlands and freshwater ecosystems with terrestrial ecosystems. They are rich in biological diversity and play important roles in sustaining ecological health and processing environmental pollutants. Korean tidal wetlands are particularly important as nurseries for economically important fishes and habitats for migratory birds. Diking, draining, tourism, and conversion to agricultural and urban uses have adversely affected Korean tidal wetlands. Recent large development projects have contributed to further losses. Environmental impact assessments conducted for projects affecting tidal wetlands and their surrounding landscapes should be customized for application to these special settings. Adequate environmental impact assessments will include classification of hydrogeomorphic units and consideration of their responses to biological and environmental stressors. As is true worldwide, Korean laws and regulations are changing to be more favorable to the conservation and protection of tidal wetlands. More public education needs to be done at the local level to build support for tidal wetland conservation. Some key public education points include the role of tidal wetlands in maintaining healthy fish populations and reducing impacts of nonpoint source pollution. There is also a need to develop procedures for integrating economic and environmental objectives within the overall context of sustainable management and land uses.

We used the Braun-Blanquet method to study the vegetation of coastal wetlands in South Korea. Three habitat types were found, i.e., salt marshes, salt swamps, and sand dunes. These plant communities were classified as: 1) two groups (five associations each) in the salt marshes that comprised either annual herbaceous halophytes (Class TheroSalicornietea), or biennial/perennial herbaceous species (Class Asteretea tripolii); 2) one group in the salt swamps consisting of five hydrophilous halo-tolerant associations (Class Phragmitetea); and 3) three groups in the sand dunes, including one association of annual herbaceous halophytes (Class Sal$oletea komarovii), seven associations of herbaceous perennial halophytes (Class Glehnietea littoralis), and one association of shrub perennial halophytes (Class ~fticetea rotundifoliae). These three habitat types accounted for the majority of the six main classifications of coastal vegetation distributed in South Korea.

Background: The structures and soil factors of Suaeda glauca-Suaeda japonica zonal communities and Phragmites australis-S. japonica zonal communities were studied in salt marshes of west and south coasts of South Korea to provide basic data for coastal wetland conservation and restoration. Results: S. glauca community mean length was 67 m and S. japonica community mean length was 567 m in zonal communities, and P. australis and S. japonica community mean length were 57 m and 191 m in zonal communities. Regarding the electrical conductivity, sodium content, and clay contents in Upnae-ri, Shinan-gun, there were significant differences among zonal communities at significance level of 0.05 for two-sided t test. However, other factors were not significantly different. Conclusions: The results indicate that multiple factors such as electronic conductivity, total nitrogen level, clay, and sodium might play important roles in the formation of zonal plant communities of salt marshes.