Study of floral composition and vegetative characteristics of porteresia bed along the upstream matla estuarine belt, Indian sundarbans

Anthropogenic disturbances pose serious threat to mangrove forest in Indian Sundarbans leading to shrinking pressure on halophytic floristic composition in this geographical locale. A vegetation study, during post-monsoon, along the upstream Matla estuarine belt belonging to central sector of Indian Sundarbans revealed a poor combination of four true mangrove species Acanthus ilicifolius L., Avicennia officinalis L., Sonneratia apetala Buch. Ham. and Exoecaria agallocha L. along with two mangrove associates Porteresia coarctata (Roxb.) Tateoka and Suaeda maritima Dumort. The lower inter-tidal region was found to be dominated by Avicennia officinalis and Exoecaria agallocha community which was sequentially replaced by Sonneratia apetala, Acanthus ilicifolius, Porteresia coarctata and Suaeda maritima towards the supralittoral zone. Porteresia coarctata, locally known as dhani ghas, appeared to be the pioneer species of mangrove mudflat in the study zone. During 1998 – 2019 study period, mean surface water salinity in the selected station was highest (25.88 ‰ ± 1.20) during pre-monsoon and lowest (9.96 ‰ ± 0.34) in monsoon months. Quadrate-wise measurements of different vegetative parameters of P. coarctata revealed that total plant height (combination of root and shoot height) was in the range of 13.34 cm – 42.43 cm (30.69 cm ± 8.48). Leaf length varied in the range between 11.03 cm and 26.5 cm. Average number of leaves was in the range of 6 – 12 per plant. Although root length and shoot length appeared to be positively correlated (r = 0.63; significant at 5% level), shoot or stem length did not appear to influence number of leaves to a significant extent (r = 0.34). The present ecological study demands for stringent monitoring along the entire stretch of the selected study area of Indian Sundarban to assess the role of anthropogenic stress on halophytic species composition and their ecological health.