Technical Applicability of Afforestation with brine-tolerative trees in the Tidal Section of River in the Southern Kyusyu

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The salt-tolerance of Hibiscus hamabo Sieb.et Zucc. (hamabo) seeds were evaluated by germination experiments and cutting methods for the purpose of regenerating hamabo forests in southern Kyusyu estuaries.Our experiments using cutting methods indicate that Hibiscus hamabo Sieb.et Zucc tolerates daily immersion in salt water prepared by dilution of sea water with a salinity of 13, 50022, 000 it S/cm and establishes roots from May to October. Furthermore, our tests showed germination rates of H. hamabo seeds in seeding beds with salinity of 0-13,500,17,500-20,000 and 22, 000-28, 000 μS/cm to be 91-97,49-66, and 7-29%, respectively. These results would demonstrate that hamabo has superior saltwater-tolerance at the seed stage compared to all other plants except mangroves, and it is one of the optimal plant species for use in afforestation around estuaries. Hamabo is widely distributed in estuaries in southern Kyushu, and could serve as an indispensable element in volunteer reforestation efforts to enhance the flora, fauna and natural ecosystem of the surrounding landscape.Our results of germination tests indicated that 1) hamabo seeds were successfully germinated in only from April to October, suggesting that the germination period of hamabo seeds is confined to the period between April to October, and that there is a period of dormancy extending from November to March, 2)collection time of the seeds, experiment season and salt water concentration were significant predictors of germination rate (P<0.001, P<0.005 and P<0.001, respectively), and 3) the maximum salt concentration at which hamabo seeds were able to germinate was 15,000〜20,000 ppm for germination in August and September. The maximum salt concentration appears to be greater than that tolerated by other halophytes, except for mangroves.