Vegetation successions of coastal wetlands in southern Laizhou Bay, Bohai Sea, northern China, influenced by the changes in relative surface elevation and soil salinity

Vegetation successions of coastal wetlands were influenced by the changes in relative surface elevation and soil salinity. In this study, the vegetation successions of coastal wetlands in southern Laizhou Bay and the factors influencing the successions were investigated by quadrat survey. The changes of relative surface elevation and soil salinity in coastal wetlands of the study region were caused by climate change, sea-level rise, coastal erosion, sedimentation, neotectonism, storm surge, seawater intrusion, invasion of Spatina alterniflora, and utilization of underground brine. The changes led to the regressive vegetation succession of coastal wetlands without the protection of sea embankment and the progressive vegetation succession of coastal wetlands with the protection of sea embankment. The invasion of S. alterniflora resulted in the regressive vegetation succession of wetlands in the riparian zone. The successions weakened the coastal wetlands' ecological capacities of carbon sequestration, pollutant purification, and resisting marine disasters, decreasing their species diversity. Some measures were proposed to resist the adverse impact of successions, such as introducing passenger water, storing water in flood season, digging 200 hm2 of ponds, and planting Salix matsudana and Tamarix chinensis around the ponds.