Structural complexity and tree species composition of mangrove forests of the Andaman Islands, India

Abstract

This study reports the mapping, structural characteristicsanddistributionofmangrovespeciesoftheAndaman Islands. 79 mangrove patches were identified using Thiessen polygons of which, 53 accessible patches were surveyed during 2014–2015. Multiple linear transects were laid at each of themangrovepatchesanddatapertainingtodiameteratbreast height, basal area and height were recorded for all mangrove trees within a 10 × 10 m quadrat laid along the transects at 50 m intervals. Altogether, 178 quadrats were laid and 25 mangrovespeciesrepresenting11familiesand14generawere recorded. Of the 3073 mangrove plants enumerated in the present study, 96.06% were composed of trees (>4 m height), 1.99% of saplings (>1 m to ≤4 m height) and 1.95% of seedlings(≤1mheight).Thenumberofspeciesperquadratranged from 1 to 9 and majority of the quadrats had 2–3 species. Density and basal area of mangrove trees ranged from 1252ha−1 to 2200ha−1 and 30.8m2/ha to 59.6m2/ha,respectively. High diversity indices (Shannon-Wiener index ranged from 1.65 to 2.24; Simpson index from 0.74 to 0.85 and Pielou’s evenness index from 0.66 to 0.84) indicated greater diversityandevendispersionofmangrovesintheIslands.The study also revealed that the mangrove forests of Andaman Islands were characterized by a mixed species composition. Most of the sites were represented by different combinations of dominant and co-dominant species, all from the family Rhizophoraceae. The present study highlights the need for conserving the mixed species mangrove forests of Andaman and Nicobar Islands and development of location-specific management plans for biodiversity conservation