Analysis of Relationship between Salinity and Top-Dying Diseases of Sundri Trees in Sundarbans, Bangladesh

Abstract

At the advent of British rule in 1765, the Sundarbans forests were double their present size (Seidensticker, and Hai, 1983; Khan, 1997). Sundarbans mangroves in Asia including Bangladesh, India, and East Africa previously contained a much fuller range of species (Seidensticker, and Hai, 1983; Khan, 1997). In the Southeast Asian region, species diversity of mangroves was previously much higher (Ellison, 1998, 2000). Although, a particular class of men made a profession of collection of wood, fish, Golpata, Goran, natural beauty, oil, honey, and wax in Sundarbans (Awal, 2007), but it is facing tremendous problems (Awal, 207, 2009, 2014). But, it is now under serious threatened through human destruction, and by ecological pollution (Awal, 2007). The cause of this dieback is still not well understood unknown. The present work has investigated one of the possible factors that might be causing this top-dying, namely the concentrations of various chemical elements present in the sediments, particularly Salinity (Na), Exchangeable K, heavy metals, though other chemical parameters such as the pH, salinity, moisture content of the sediment and nutrient status were also assessed. (Awal, 2007). Na has no relationship with the amount of top-dying of Sundri trees in Sundarbans. However, a serious killer disease (top dying) of H. fomes in Sundarbans is affecting millions of the trees (Awal, 2007). The loss of H. fomes will have a major impact on the Sundarbans mangrove ecosystem, as well as lead to economic losses. A questionnaire survey was conducted among different groups of people inside and outside of Sundarbans to explore local perceptions as to the possible causes of top dying. This confirmed the increase in top-dying prevalence (Awal, 2007). Most of the elements including Salinity of soil and water studied had no significant correlation with the top dying of Heritiera fomes. However, Sn, Exchangeable K, and soil pH were significantly related, and three elements, namely Pb, Zn, Ni, were also close to significance. Sn concentration is negatively associated with top dying. Soil pH varied significantly in the different plots. Exchangeable K was positively associated with the tree diameter whether the top dying was severe or mild.