Effect of reclamation on the annual and seasonal characteristics of Spartina alterniflora population in Tiaozini coastal wetland

In order to explore the impact of reclamation on the expansion of Spartina alterniflora (a kind of invasive species)population, the annual and seasonal changes of Spartina alterniflora population distributed inside and outside the embankment was observed in the Yancheng coastal wetland, Jiangsu Province from May 2017 to July 2018 with the help of unmanned aerial vehicle (UAV)monitoring technology. Combined with field monitoring data, the effects of soil moisture content, soil salinity, growth elevation, and surface water level on the growth and population area of Spartina alterniflora were analyzed. The results showed that the reclamation significantly reduced the expansion rate of Spartina alterniflora, and the area inside the embankment increased by 21% during the observation period, while the area outside the embankment increased by more than 400%. The population expansion inside and outside the embankment of Spartina alterniflora had obvious seasonality, and the seasons of expansion were autumn and summer respectively. The soil moisture content and salinity in the reclamation area decreased by 25% and 50% respectively compared with the area outside the embankment. There was a significant positive correlation between the height of Spartina alterniflora and the elevation of the growing area (PSpartina alterniflora population was significantly positively correlated with surface water level (PSpartina alterniflora, and seawater changed the soil water and salt conditions in the reclamation area, and thus inhibited the expansion of Spartina alterniflora.