A Study On Adaptability Of Mangrove Species To Water Salinity

Mangrove forest is an important ecological and economical resources in the world. It is not only breeding grounds for birds, fish, crustaceans, shellfish, reptiles and mammals, but also gathering place for sediments, pollutants, carbon source and nutrients. However, as the un-reasonable excavation and utilization in coastal areas, the area of natural mangrove are reducing fleetly. As a result, the function of mangrove ecosystem are degraded in an all-round way. So building artificial mangrove wetland and restoring the mangrove ecosystem has become one of hot research in mangrove fields.Studies show that the salinity can be one of factors that limiting the mangrove seedling become an forest. Limited information exists, however, concerning the effects of salt stress on both of the ecological, physiology and morphology indexes of mangrove plant reaction. In2013, we treated1year old seedlings of Sonneratia apetala (Sa) and Aegiceras corniculatum (Ac) with different salinity levels (0‰,5‰,10‰,15‰,20‰,30‰,40‰and50‰). In2012, we cultivate1year old seedlings of Ac and the candle seedlings of Kandelia candel (Kc) and Bruguiera gymnorhiza (Bg). We want to explore the ecological, physiological and morphological adaptability of four mangrove species to water salinity. Ecological indexes included plant height, basal diameter, biomass, number of leaves, leaf length and width; physiological indexes contained net photosynthesis rate, stomata conductance, transpiration rate and total chlorophyll; besides, paraffin method was used to observe morphological structure. The result indicated:(1)Study on effects of Ac and Sa seedlings under different water salinity, show that, increasing of the salinity level could benefit to mangroves (≤30%o).Sa grew well under15%o salinity level and Ac grew well0%o and5%o salinity level. As the salinity level increased, the growing trend of physiological indexes such as net photosynthesis rate, stomata conductance and total chlorophyll first increased and then decreased. The layers of palisade tissue_increased when the salinity level at15%o and20%o for Sa, while it would be0‰and5‰for Ac. Therefore, Sa is suitable to be planted in artificial wetland as dominant specie and constructive specie, and Ac is a kind of companion specie for its low amount of height.(2)Study of adaptability of Ac seedlings and Kc and Bg candle seedlings under fresh water, found thar three mangrove plants are able to survive in fresh water breeding. The propagule germination rate of Bg is higher than Kc’s. Ac is grow slowly, and Ko is the best above all. The net photosynthetic rate and stomatal conductance of these three are increased with the time passing by. The increment are, Kc>Bg>Ac; With fresh water breeding, the leaf anatomical structure of three kinds of mangrove plant all have thicker cuticle, cortex contains tannin substances. Above all, Kc with the most exuberant, are suitable for growing in freshwater man-made mangrove wetlands.