AGE-SPECIFIC SURVIVAL, MORTALITY AND REPRODUCTION, AND PROSPECTS FOR CONSERVATION OF LIMONIUM-DELICATULUM

1. Limonium delicatulum is a salt-tolerant cushion plant. Survival, mortality and reproduction were investigated, and their implications for the conservation of naturally growing populations in the Mediterranean region of Egypt were assessed. 2. The total annual seed output by the entire population was computed to be c. 76000 seeds. About 29.5% of the seeds had the potential to germinate in soil, and out of these germinable seeds, about 7.9% gave seedlings. The juvenile plants comprised about 5.9% of the seedlings, while about 65% of juveniles reached mature reproductive stage. 3. The survivorship curve, life table and fecundity schedule reflected high mortality of seeds and seedlings. Juveniles and adults of age 7 years showed high expectation of future life. The net reproductive rate was 0.36, indicating failure of the population to attain 'positive' growth and reproduction. The estimated intrinsic rate of increase was -0.071 per capita year-1. The average generation time of the species was 14.4 years. 4. The percentage of dead whole individual plants or partially dead individuals in the population increased with age. The number of dead individuals, or dead rosettes per individual in the oldest adult cohort, exceeded respectively the live individuals or rosettes. A smaller fraction of live phytomass was allocated to roots than to stems, leaves or (in adults) inflorescences; the fraction was smaller in adults than in juveniles. The live/dead phytomass ratios were greater than unity in roots and stems. The leaves showed live/dead ratios of less than unity, being 0.69 in juveniles and 0.34 in adults. 5. Vegetative activity occurred throughout the year with minimum cushion leafiness and leaf appearance rate during April and May. There was a significant negative linear correlation between cushion leafiness and age of plants. 6. The following recommendations are essential to conserve the species and its habitats: (i) creation of small-scale natural salt-marsh reserves within the developed agroecosystems; (ii) professional botanical/ecologial management of these natural reserves; (iii) ethnobotanical knowledge of the species; and (iv) ecological research on in situ and ex situ survival and propagation strategies of the species.