Figure 1. The location of study site in Zhangjiang Estuary, Yunxiao, Fujian, China. Salinity in oligohaline upstream site ranged from 0‰ to 6‰, salinity in mesohaline midstream site ranged from 13‰ to 18‰ and salinity in euhaline downstream site ranged from 29‰ to 32‰.
The field transplant experiment was carried out in the estuary of the Zhangjiang River in Yunxiao Country, Fujian Province, China (23°53’-23°57’ N, 117°23’-117°30’ E) (Figure 1). In this area, the mean annual air temperature is 21.5 °C and annual mean tidal variation is 2.32 m. According to the previous study, three study sites with different salinities along the estuary of the Zhangjiang River were chosen for field transplant experiment (Zhang et al. , 2012). The salinity in oligohaline upstream site ranged from 0‰ to 6‰, in mesohaline midstream site ranged from 13‰ to 18‰ and in euhaline downstream site ranged from 29‰ to 32‰, respectively. All of these sites experienced a semidiurnal tide.
To evaluate the effect of salinity on tillering, one-month old seedlings of S. alterniflora were collected and held in greenhouse in April 2014. After 1 recover period of one week, 90 healthy seedlings were selected and planted into 1× 1 m plots in the unvegetated mudflat at each of the three sites (n = 6 seedlings × 5 plots × 3 sites). Each site has 5 plots at 5 m intervals as biological replicates. All 15 plots were located within 35 cm vertical elevation of each other and had similar durations of tidal flooding (within 30-35 min per tidal period). The number of tillers and the plant height of each seedling was counted every month for 4 months after transplantation.