AUTECOLOGY AND CONSERVATION CONSIDERATIONS OF AVICENNIA MARINA(FORSSK.)VIERH IN THE GULF OF AQABA, EGYPT

SUMMARYThe South Sinai is one of the most spectacularly beautiful landscapes on Egypt, some of which have in recent years been set aside as national parkland. The most famous of these parks (and in fact Egypt’s first national park) is found at the far southern tOnly two mangrove plants are recorded from Egypt. The most widespread one is Avicennia marina (Avicenniaceae). It is the only mangrove species growing in Ras-Mohamed and Nabq protectorates. This species is tolerant of relatively high salinity, together wiThe following main findings were obtained from this study:1. The plant populations showed two phonological periods of flowering and fruiting within a single year.2. The correlation between age-class distribution and the percent of total number of adult individuals in the population of Avicennia marina is showed that the percentage of adults decreased with age in the different habitat types.3. The density of respiratory roots at Ras-Mohamed is greater than those at Nabq where it give the highest number over 300 per meter square and the highest length (47 cm).4. The pigment content of leaves along a sea-land transect, was increasing in the seaward.5. The soils of the study sites are, relatively, rich in organic matter and are generally sandy, calcareous and saline-alkaline.6. Analysis of major elements in soil showed that potassium was the dominant element followed by phosphorus then nitrogen, while minor elements showed that iron was greater than zinc, manganese and copper.7. The results of the survivorship (Lx) for all populations exhibited extremely high mortality from flower bud to seedling stage in all sites.8. Low mortality showed slight decline in adults in all sites. Plants in the Sand mound habitat showed sharp decline at age 0.5-15 years.9. The age-specific mortality rates (qx) attained the highest values in flower bud and fruit stages in all sites then values decreased in seedling and adult stages.10. The killing pow¬er (kx) value increased sharply from flower bud to the germinable seed stage (0.4) then sharply decreased during seedling and adult stages.11. The mean expecta¬tion of future life (ex) showed high value at age 15 years in all sites, except sand mounds which showed high value at age 25 years and salt flat at seedling stage.12. The highest values of (lxbx) were shown at age 25 years in all stands except sand mounds, while the reproductive rate (Ro) of both sand mound and intertidal site were significantly higher than the remaining sites.13. The reproductive value (Vx) was generally high at shoreline, intertidal and Ras-Mohamed sites than in sand mounds and salt flats.14. The generation time (T) ranged from 25.6 years in the salt flat to 53.8 years in the sand mounds. The intrinsic rate of increase per capita per annum was close to zero indicating almost stable populations.The following recommendations towards the conservation of Avicennia marina are put forward:(1) As much as possible of plant communities and the populations of the species should be conserved from human activities.(2) Harvesting should be restricted to the oldest individuals in the population.(3) Since vegetative propagation appeared to be negligible under natural conditions, the route to population increase lies in creating conditions which are conducive to flowering, seed setting and seedling establishment.(4) Creation of small scale natural mangrove reserves within the coastal area of the Red Sea. For adequate conservation, these natural reserves should be under professional botanical-ecological management(5) Extensive ecological research on in situ and ex situ populations for creating conditions conducive to optimum survival and reproduction. More experimental studies are needed on in situ and ex situ propagation well as seed storage in a gene bank.