An analysis has been made in the Sundarbans mangroves to relate the
community structure and distribution of species with soil salinity and pH gradients. Soil
salinity (13.0 to 31.2 ppt) decreased with increasing distance from the tidal coast but no such
trend was noticed in soil pH (7.0 to 7.9). Frequency of tidal inundation seemed to affect soil
salinity. Acanthus ilicifolius, Avicennia alba and A. marina dominate the sites having regular
diurnal tidal inundation. Maximum complexity index was noted on the least saline zone.
Ecological group classification indicates that Avicennia marina and A. officinalis can tolerate
wide range of soil salinity while Aegiceras corniculatum, Ceriops decandra, Dalbergia spinosa,
Derris trifoliata and Excoecaria agallocha are restricted to low salinity areas. Most species had
an optimum pH range except Avicennia marina, which occurred in varied pH conditions.
Acanthus ilicifolius was relatively insensitive to pH and salinity gradient due to its wide
ecological amplitudes.