Agriculture, Forestry and Fisheries
Volume 3, Issue 5, October 2014, Pages: 329-340
Received: Jul. 30, 2014;
Accepted: Aug. 6, 2014;
Published: Sep. 20, 2014
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Awal, Mohd Abdul, Environmental Scientist, Ministry of Environment and Forest, Health & Pollution Research Farm, Long Island City, New York, USA
Natural forest resources like 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, where approximately two-thirds of all species and 70% of the major vegetation types with 15% of terrestrial species in the Bangladesh-India-Malayan realm have already been destroyed (Ellison, 1998, 2000). Despite this designation, this natural forest resources (Sundarbans) in Bangladesh has been facing tremendous problems, including that of dieback (top-dying), shrimp farming, human destructions, deforestations, illicit fellings, miss-management of the main tree species (Heritiera fomes) which is affecting millions of trees (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 heavy metals, though other chemical parameters such as the pH, salinity, moisture content of the sediment and nutrient status were also assessed. 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). Despite various hypotheses as to the causes of this top-dying, the underlying causes are still not well understood. The present work has explored some of the possible factors involved, focusing particularly on the relationship between the amount of top-dying in different places and the concentrations of a number of chemical elements present in the soil and water, in order to test the hypothesis that chemical pollution might be responsible. Other factors such as the pH, salinity and nutrient status were also assessed. The vegetation structure was assessed in terms of tree height, bole diameter, species present, and regeneration status; and the intensity of top-dying within the plots was recorded on a rank scale. Most of the elements 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 (Awal, 2007).
Awal, Mohd Abdul,
Analysis of Effluent Discharge in to Natural Forest in Bangladesh, Agriculture, Forestry and Fisheries.
Vol. 3, No. 5,
2014, pp. 329-340.
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