Abstract
Indian east coast in West Bengal, Orissa, Andhra Pradesh, Tamil Nadu and the Andaman and Nicobar islands supports various types of mangrove formations such as deltaic, estuarine, backwater and sheltered, insular bay types. The present study is an effort to collect ecological information on zonation of mangrove species based on phytosociological methods at four forest sites in Mangrove Ecosystems of Orissa coast. A total of 16 species were recorded at Thakurdia site, 20 tree species at Dangmal site, 24 tree species at the Bhitarkanika forest site and 17 tree species at Kakranasi forest site. The Bhitarkanika site has the highest number of species among all the four study sites. This block along with Dangmal is in the core area of the Bhitarkanika wildlife sanctuary. Availability of fresh water through Bhitarkanika (Maipura) and Brahmani rivers and saline water from sea help wide range of niches for different species to occur and, thus, species diversity is the highest in this mangrove ecosystem. A clear zonation pattern so characteristically reported by authors from different mangrove forests of world is absent in the study area. The mangrove species in study area occur as 'ecological mosaics' scattered over the forest blocks. Such mosaic formations could be linked to the very dynamic nature of the forest blocks in the study area with ecological functions such as tidal inundation, seed/propagule dispersal etc. operating equally throughout the area. Rhizophora and Kandelia species which are characteristic of the riverbank vegetation were seen deep inside the forest blocks, thus adapting to different type of niches. The riverbank-like niche is provided by innumerable creeks that criss cross the forest blocks and thus favouring these species that grow on the banks. Based on these habitat types a new classification of mangrove forest types of Bhitarkanika forest ecosystem has been proposed through present study.
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