Species composition, abundance and diversity of mangroves in selected sites in Amprara District in the east coast of Sri Lanka

Sri Lanka is gifted with about 15,670 ha of mangrove habitats which are scattered along the coastal zone of the island. However, most of the studies on mangroves are confined to the western, north-western and southern parts of the country. Although it is been neglected, Eastern province shares 28% of the mangrove cover of the country. Thus, the main objective of the current study was to determine the distribution, abundance and diversity of true mangrove species in Pottuvil, Heda oya, Ragamwela, Panama, and Okanda mangroves in the Eastern province of Sri Lanka. Mangrove vegetation was sampled using belt transects of 5 m in width laid perpendicular to the shoreline and across the water-land gradient. True mangrove species in each transect was identified and counted. Height and DBH (Diameter at Breast Height) were recorded. Relative density, relative frequency, relative dominance and the IVI (Importance value index) of the species in each mangrove ecosystem were calculated. Shannon diversity index (H’), Shannon Evenness (E’) and Simpson index was used to compare the diversity between sites. Nine true mangrove species were recorded in Panama lagoon and the least number of species (3) were recorded from Ragamwela creek. Highest Shannon diversity value (H’ = 1.7) was obtained for the Panama mangrove which was followed by the Heda Oya Estuary mangrove (H’ = 1.1). Lowest Simpson index was recorded in Panama lagoon (0.22). Nearly half of the true mangrove species (11) that have been recorded from Sri Lanka occurs in the five study sites. They belongs to seven families and eight genera. More research is needed to understand the ecological aspects of theses mangroves as these systems have not been studied for the last thirty years. It is recommended that immediate action should be taken by the government to prevent distractive anthropogenic activities in these mangrove ecosystems

Seed germination and predation of the tropical monocarpic palm tree Corypha umbraculifera

Corypha umbraculifera L., the long lived monocarpic palm belonging to Arecaceae, is rare in the wild and is a possible candidate, which can be developed as an economic plant in Asia. However, little information is available about propagation of this species from seeds. Thus, we aimed to investigate the basic seed biology of this species and to facilitate its propagation and conservation. Effects of light and temperature on seed germination were studied. Morphology of seed germination and embryo: seed ratio were recorded. Seed predation percentages, initial moisture content and nutrient content were determined and optimum storage conditions identified. The highest germination percentage was in light/dark at 25 ˚C. In two trials, of 38.66 and 31.66 % of the seeds were predated. Total energy value of seeds was higher than that of Cocos nucifera, a common known polycarpic palm. Seeds of C. umbraculifera have morphophysiological dormancy as evidence by embryo growth prior to radicle emergence and the relatively long time (42-49 days) taken for completion of germination. Low predation percentage and slow germination rate indicate that the predator satiation hypothesis is not sufficient to describe the evolution and existence of monocarpy in C. umbraculifera. Decreased viability during dry storage at ambient room conditions and a moisture content of 16 ± 3 % indicate that seeds have intermediate storage behaviour. Storage in open polythene bags at 8 ˚C is suggested as the best storage condition for C. umbraculifera seeds