Abstract:

Exotic species are only used in some places in China for mangrove restoration, as they often perform better than native species on these desired restoration sites often with highly stressful habitats. Here, we conducted a mesocosm experiment to detect the differences of survivability between exotic and native mangrove seedlings under accretion/erosion disturbances on tidal flats, using exotic species Laguncularia racemosa and native pioneer species Avicennia marina as examples. Our results demonstrated that for both species the erosion resistance of seedlings correlated positively with root-to-shoot length ratio. Sediment accretion disturbance inhibited the root development of seedlings so that the root-to-shoot length ratio increased, while sediment erosion promoted root elongation with the root-to-shoot length ratio decreased. Compared with the native species A. marina, exotic species L. racemosa seedlings have greater root-to-shoot ratio, and are thus more resistant to erosion with better adaptability to sediment dynamics via root elongation. Our study indicates that the exotic species L. racemosa are more adaptable to erosion disturbances on tidal flats than the native species A. marina. These findings shed light on the selection of tree species and suitable planting sites for mangrove restoration, and might provide helpful insights into assessing the risk of species invasion in mangrove ecosystems.

Key words: Accretion/erosion, Laguncularia racemosa, Avicennia marina, seedling, stability