PLANT DIVERSITY AND STRUCTURAL DYNAMICS OF MANGROVES IN THE SOUTHWEST COAST OF KERALA, INDIA

Mangroves are the plants adapted to strident environment with unvarying inundation of the soil and extremely diverse salinities, habitual in river banks, sand flats and coastlines of the tropics and subtropics of the world. Mangrove vegetation in six geographical regions of Kollam on the Southwest coast of India was selected to study the phytosociological characteristics and diversity indices. We analysed the pattern of mangrove species diversity, density and basal area and similarity parameters. Totally, 12 species of mangroves belonging to 8 genera and 6 families were identified; Rhizophoraceae and Avicenniaceae were the most dominant group represented. Highest density was recorded for Avicennia officinalis (3760stems/ha), followed by Avicennia marina (3721stems/ha). Avicennia officinalis is the most common mangrove counted with the highest Important value index (IVI) and Relative IVI; 64.19 and 21.40 respectively. Shannon- Weiner Index of diversity ranged from 2.002 to 3.11; species richness from 0.429 to 1.033 and the similarity in floral composition varied from 0.33 to 0.66. The sites selected were distinct from one another and the species diversity varied from one place to another; influenced by the climatic, biotic, anthropogenic stresses.