Plant distribution along an elevational gradient in a macrotidal salt marsh on the west coast of Korea

•Salt marsh plant species showed a distinct zonation according to elevation.•Plots formed four clusters based on similarities in plant community composition.•Suaeda japonica occurred in the widest range of elevation and salinity.•There was considerable variation in salinity among the high-elevation plots.•Soil available phosphorus had a significant negative correlation with elevation. The distribution of halophytes in salt marshes is generally determined by environmental gradients, and it is important to identify the principal factors involved. This study recorded how marsh plants, which have received limited attention, were distributed along elevational gradients, and investigated the environmental factors affecting their distribution on the Siheung Tidal Flat, which has one of the largest tidal ranges in the world. Plant and soil samples were collected in September 2015 from 203 plots that had been randomly selected in the intertidal zone. Soil salinity in the high-elevation plots varied over a wide range. Each halophyte species had a distinct zonation according to elevation. Cluster analysis classified plots into four clusters reflecting plant community composition (Cluster 1 at high elevation, defined by Suaeda glauca, Zoysia sinica, and Phragmites australis; Cluster 2 at mid-high elevation, defined by Phacelurus latifolius; Cluster 3 at low elevation, defined by Suaeda japonica; Cluster 4 at mid-high elevation, defined by Carex scabrifolia). Non-metric multidimensional scaling indicated that the distribution of S. japonica was strongly influenced by elevation and flood frequency, whereas that of P. latifolius was negatively influenced by soil salinity and soil cations (Na+, Mg2+, K+, Ca2+). Understanding the relationship between halophyte distribution and environmental factors along elevational gradients in a natural salt marsh provides important ecological information that may contribute to salt marsh restoration.