GROWTH PERFORMANCE AND SITE SUITABILITY OF Lumnitzera racemosa WILLD. IN THE SUNDARBAN MANGROVE FOREST OF BANGLADESH
Conservation of the Sundarban mangrove forests of Bangladesh is a most important and challenging contemporary problem. Enrichment plantations with Lumnitzera racemosa were raised in the poorly regenerated areas of the Sundarban for the purpose of conservation of the species, enhancement of coastal protection against storms, sea-level rise and erosion, and enabling of natural products such as fish, crabs and wood. The total duration of the field experiment was thirteen years, spread over the period between January 2005 and January 2018. The height, diameters at breast height (dbh), mean annual increment (MAI) and survival of twelve years old Lumnitzera racemosa trees differ significantly at different spacing between moderate and strong saline zone of the Sundarban. The highest height (m), dbh (cm) and survival (%) have been found 7.31±0.09, 6.79±0.22 and 88 in the spacing 2m x 2m under moderate saline zone as well as the highest MAI for height 0.61m and for dbh 0.57cm were found in the same spacing and same saline zone. All these findings significantly reflect that growth performance of twelve years old Lumnitzera racemosa trees planted in moderate saline zone was better on 2m x 2m compared to 1.75m x 1.75m and 1.5m x 1.5m spacing. It is observed that the hydrological conditions in moderate saline zone are better supportive for mangrove growth than strong saline zone of the Sundarban. Planting of seedlings were done on low tide that helps ensure proper planting depth, which is very important for successful establishment of L. racemosa plantation. Nursery propagated seedlings maintained the highest survival rate. L. racemosa species require a certain moistening and drying regime for their survival and will therefore only grow within a specific tidal range. Enrichment planting with Lumnitzera racemosa in the poorly regenerated areas of the Sundarban can accelerate the return of a productive forest capable of sustaining environmental, economic and social activities of local communities, dwelling in the adjacent areas of the Sundarban, thus declining pressure on primary forests.