| In this study, field experiments were carried out in Tongan bay, Xiamen, China. Kandelia candel seedlings were planted at various topographic sites in an intertidal zone of Tongan bay. The experimental plots were on a slop and showed a maximal elevation difference of 1.6 m. Seven experimental plots were set up in forest areas of intertidal zones. The plots were naturally submerged with 20-30‰saline water twice a day. Salinity, pH and the concentration of several ions in the soil were similar in all the plots. The survivalrate of propagules of Kandelia candel and the growth of its seedlings were measured every 3 months to find the critical tidal flats suitable for Kandelia candel. These findings would provide guideling information for appropriate tidal flats in a mangrove restoration program.Leaves of Kandelia candel planted in mangrove habitats along the intertidal gradient were collected from the Tongan bay. C, N and tannins concentrations and the photosynthestic performance of Kandelia candel in each sampling site were monitored. Responses of concentrations of C, N and tannins and the growth of Kandelia candel were study. It was predicted on the basis of carbon-nutrient balance (CNB) hypothesis that the concentrations of tannins would decline and the growth increase in response to waterlogging.Quantitative survey and research on barnacle species attaching to mangroves, the relationship between barnacle quantity and biological and ecological factors and barnacles harm to artificial young mangroves were studied. The aim of our study was to evaluate mangroves forestation in the intertidal and to develop a better understanding of factors influencing its regeneration. The results were showed as following.1. This study determined the effect of elevation on the survival and growth of mangrove seedlings during the establishment period. The results showed significant changes in growth and survival rate in response to topography. At 1.6 m of Huang sea-leval, Kandelia candel seedlings showed the best growth and the higest survival rate. Ascertain the critical tidal flats for Kandelia candel in Xiangan Bay, Xiamen. For Kandelia candel seedlings, the critical tidal elevation in Xiamen is 1.0 m of Huang sea-level.2. Electron transport rate (ETR) and maximal quantum yield of PSⅡphotochemistry (Fv/Fm) of Kandelia candel seedlings tended to increase with increasing elevation. While the tidal elevation is 0.2 m-0.6 m of Huang sea-leave, actual PSⅡof Kandelia candel seedlings is inefficient and photodamage is serious. The results showed that waterlogging have a great effect on photosynthesis. While the tidal elevation is more than 0.6 m, the photochemistry efficiency is normal.3. Different waterlogging durations of tidal immersion had different effects on the contents of C, N, tannins and Chlorophyll in leaves of Kandelia candel seedlings, which were planted at various topographic sites. Tannins concentrations and C/N ratios tended to decrease with decreasing elevation. The results showed that changes in C, N and tannins concentrations in response to waterlogging. This indicates that longer waterlogging time resulted in lower C/N ratios. The response of C, N and tannins in leaves to waterlogging was consistent with carbon-nutrient balance hypothesis.4. Kandelia candel communities for one year were thinned. Four thinning density were set up, which were 20 cm×20 cm, 30 cm×30 cm, 50 cm×50 cm and 100 cm×100 cm. Reveals the influences of the serial measures of thinning, the space of initial plantation should be properly close (50 cm×50 cm). Community thinned in a certain extent can increase their growth.5. The investigation on the barnacles attaching to the stems of Kandelia candel in the forest zone of Xiamen was carried out in September 2007. The results showed the barnacles quantity attaching to mangroves had positive correlation with their habitat seawater salinity, tide inundating depth and tide flooding ratio. Large scale of barnacles attaching to young mangrove tree reduced the increment of tree height and trunk diameter, caused tree trunk in deformation and even death.
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