Native salt-tolerant grass species for habitat restoration, their acclimation and contribution to improving edaphic conditions: a study from a degraded mangrove in the Indian Sundarbans

Abstract

The Sundarbans is the largest continuous block of mangrove distributed over both India and Bangladesh and is threatened with pronounced erosion and mudflat degradation in its western reaches. Since 2013, considerable progress has been achieved through the restoration of highly degraded mudflats by the extensive utilization of four native grass species plantings, Porteresia coarctata, Myriostachya wightiana, Paspalum vaginatum, and Sporobolus virginicus. These grasses proved to exhibit the highest survival (80–90%) in the lower and middle intertidal zone and during the last three years (2013–2016) almost 6000 m² area have been restored by the growth of these grasses. Increased osmolyte synthesis under degraded conditions in these native grasses offered osmotic protection and helped to expand and restore the mudflat to an elevation suitable for mangrove establishment. The rhizosphere of the four grasses was engaged in the decomposition cycle, releasing more nutrients, more nutrient cycling soil microbial enzymes, and encouraged high densities of nutrient cycling bacteria. The study demonstrates that stabilization and reclamation of the denuded mudflat by halotolerant grasses is an essential prerequisite for any successful mangrove restoration program. The facilitative role of the salt marsh is crucial to aid colonization by mangrove propagules.