Background

Zonal distribution of higher plants in salt marshes has been studied extensively for over a century. However, mechanisms of generating the segregation of salt marsh plant species are poorly understood (Caçador et al. 2007; Emery et al. 2001). In order to explain plant zonation, shore height is frequently used as an indicator of abiotic gradient in intertidal ecosystems. This is based on the implicit assumption that shore height is directly correlated with inundation frequency and/or duration (Bockelmann et al. 2002; Sánchez et al. 1996). The objective of this study was to determine structures of zonal communities and factors that might control salt marsh plant patterns and zonations.

Methods

The structures and soil factors of two zonal community types of South Korea were monitored and can be used as basic data for conservation and restoration of coastal wetland ecosystems (Fig. 1). Six Suaeda glauca-Suaeda japonica zonal communities (Table 1, No. 1–6 in 1998) and five Phragmites australis-S. japonica zonal communities (Table 1, No. 1 in 1998, No. 2–3 in 2005, No. 5–6, 2015) were sampled from the west coast to the south coast of South Korea.

Fig. 1
figure 1

The first community length of occupation (d1, m) and second community length of occupation (d2, m) in salt marsh

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Table 1 Zonal community name, first community length of occupation, second community length of occupation (d1 and d2, m), locations of six Suaeda glauca-S. japonica, and five Phragmites australis-S. japonica zonal communities
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Results and discussion

S. glauca community mean length was 67 m and S. japonica community mean length was 567 m in zonal communities, and P. australis community mean length was mean 57 m and S. japonica community mean length was 191 m in zonal communities (Table 1). S. glauca community was found in Unpo-ri, Songhyun-ri, and Chulpo-ri. The community height was 70–80 cm. Its coverage in study areas was 70–80 %. The S. japonica community was found in both S. glauca-S. japonica and P. australis-S. japonica zonal communities. Its community height was 35–45 cm. Its coverage in study areas was 85–100 %. The area of salt marshes in Chulpo-ri and Sinduk-ri was 4–5 km2. P. australis communities were found in Woopo-ri, Nongjoo-ri, and Dongkeom-ri. Community height was 64–125 cm with coverage of 85–100 %.

Soil factors in S. glauca, S. japonica, and P. australis communities of Upnae-ri, Shinan-gun, are shown in Fig. 2. Electrical conductivity ± SE in S. glauca, S. japonica, and P. australis communities were 1.38 ± 0.0015, 1.28 ± 0.0045, and 1.01 ± 0.0055 mS/cm, respectively (n = 10). Total nitrogen ± SE in S. glauca, S. japonica, and P. australis communities were 0.21 ± 0.0026, 0.55 ± 0.0026, and 0.69 ± 0.0025 mg/g, respectively (n = 10). Higher total nitrogen level in S. japonica community than that in S. glauca community might be due to higher density in S. japonica community. Higher total nitrogen level in P. australis community might be due to higher biomass in P. australis community. Total phosphate ± SE in S. glauca, S. japonica, and P. australis communities were 0.05 ± 0.0008, 0.04 ± 0.0009, and 0.04 ± 0.0005 mg/g, respectively (n = 10). Such slight difference might be due to dilution of inland and coastal wastewater by tide. Sodium contents ± SE in S. glauca, S. japonica, and P. australis communities were 15.3 ± 0.0137, 12.3 ± 0.0052, and 5.8 ± 0.0104 mg/g, respectively (n = 10). Clay content ± SE in S. glauca, S. japonica, and P. australis communities were 26.0 ± 0.0344, 25.0 ± 0.0446, and 8.0 ± 0.0274 mg/g, respectively (n = 10). Regarding the electrical conductivity, sodium content, and clay contents in both S. glauca-S. japonica and P. australis-S. japonica communities and total phosphate in S. glauca-S. japonica community in Upnae-ri, Shinan-gun, there were significant differences among zonal communities at significance level of 0.05 for two-sided t test. However, there were little differences in total phosphate levels.

Conclusions

Halophyte distributions are related to multiple reactions of flooding and salinity concentrations (Benito et al. 1990; Caçador et al. 2007; Mert and Varder 1977). In South Korea, halophyte distributions have been determined for soil-water relation and soil texture (Ihm et al. 2007; Rogel et al. 2001) as well as flooding frequency (Lee 1990). A combination of multiple factors such as flooding, soil salinity, and competition have been suggested to play important roles in the formation of zonal plant communities in salt marshes (Pennings and Callaway 1992; Silvestri et al. 2005).

Fig. 2
figure 2

Electrical conductivity, total nitrogen, total phosphate, sodium, and clay contents (mean ± SE) in S. glauca, S. japonica, and P. australis communities in salt marshes of Upnae-ri, Shinan-gun

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