Monitoring the Monthly Expansion Pattern of Pioneer Vegetation in Tidal Flats Using a Terrestrial Laser Scanner

Research on the expansion pattern of pioneer vegetation in tidal flats is important, because this pattern affects the development of both topography and ecology. This study aimed to determine the monthly expansion patterns of seedlings and tussocks by using terrestrial laser scanning (TLS). Overall change process research and spatial analyses of both seedling recruitment and tussock development were carried out in this work. The results show that the overall change in pioneer vegetation reflected an expansion toward the shoreline in the first year and then a northward colonization in the second year. Moreover, positive feedback effects were observed between vegetation colonization and sedimentation accretion. Colonization accelerated the depositional process at the study site. Moreover, sedimentation accretion in the northern subarea, which is located close to the seawall, promoted the colonization of vegetation in this region. A strong spatial relationship was observed between seedling recruitment and tussock development. Tussocks tended to force seedlings to expand outward by squeezing the established space of the seedlings. Moreover, seedlings were densely concentrated within a certain distance from tussocks. The distances between seedlings and tussocks tended to shorten annually as the entire vegetation area underwent the expansion process. The average distance between seedlings was found to be concentrated from 10 to 20 m. The monthly vegetation expansion process was studied on small and medium scales in this work, revealing the advantages of TLS technology in rapidly acquiring data with high resolution and high precision.