Is Heritiera fomes Buch. Ham. less adapted to the present conditions of the Indian Sundarbans compared to other mangrove species?

Abstract

The Sundarbans forest forms one of the largest mangrove vegetation in the Bengal Basin. The name indicates dominance of the tree species Heritiera fomes Buch. Ham., locally known as ‘Sundari’ because of its elegance. Explosive demographic pressure and indiscriminate exploitation of natural resources caused imbalance in this ecosystem. Moreover, reduced fresh water influx and increased sedimentation appeared to be an increasing problem for navigation that in turn, led to elevated soil salinity. In the Indian part of this forest, scarcity of Heritiera fomes can be attributed to these manual and environmental adversities. In comparison to the other predominating species in Sundarbans, H. fomes is less equipped in its leaf anatomical adaptations and water-use management. Considerably thin cuticle and high stomatal frequency encourage water efflux; whereas, poorly developed water storage tissue and low frequency of terminal tracheioids weaken the water retention mechanism. This inefficiency is reflected well by the transpiration rate and stomatal conductance that continuously increase even beyond 1600 μmol m-2s-1. In H. fomes, assimilation potential declines beyond 1250 μmol m-2s-1 PAR, which unlike the other taxa, can be attributed to the poorly developed palisade tissue and low nitrogen content in leaf. The optimum leaf temperature for photosynthesis