Diversity, stand structure, and zonation pattern of mangroves in southwest coast of India

Abstract

This article contributes to the diversity and stand structure of the mangroves in Kerala, India, using multivariate methods. Floristic diversity of mangroves comprised 18 species of true mangroves, of which Sonneratia alba, Avicennia alba, and Ceriops tagal were found to be rare, whereas Bruguiera parviflora was extinct in the state. Structural analyses revealed the importance of Avicennia officinalis and the domination of Acanthus ilicifolius. The mean stem density ranged from 10 to 13846 no/ha, whereas the mean basal area ranged from 0.02 to 20.19 m2/ha. Multivariate analysis of true mangroves could be classified into five floristic groups based on stem density. Group 1 comprised Rhizophora mucronata, R. apiculata, Ceriops tagal, Kandelia candel, Sonneratia alba, and S. caseolaris, which were seen in the fringing zone. A combination of Group 2 and Group 3 comprised Avicennia marina, A. alba, Lumnitzera racemosa, Acrostichum aureum, Excoecaria agallocha, E. indica, Avicennia officinalis, Bruguiera gymnorrhiza, and Aegiceras corniculatum, found in the intermediate zone, whereas Bruguiera sexangula and B. cylindrica occurred in the landward regions which constituted Group 4. Acanthus ilicifolius, having a widespread distribution, was found in all the three zones represented by Group 5. Tidal elevation was found to be important in shaping the observed zonation.