J. Sci. Foundation, T(1):37-51, June 2009 ISSN 1728-7855 A CRITICAL REVIEW OF LITERATURE ON TOP DYING OF SUNDRI IN THE SUNDARBANS M A Rahmant, A K F Hoque2, M G Rakkibu2 and K. Misbahuzzaman' ABSTRACT Sundri (ieritiera fomes) isthe most important tree species of the Sundarbans. Top dying of sundri is a very widespread disease syndrome. A chronological account of top dying of sundri and related knowledge during the period 1921 to 2003 has been provided. New insights about the possible causes of top dying of sundri are highlighted. Increased soil salinity is considered as a general predisposing factor for sundri in the Sundarbans while reduced soil aeration is considered as the primary cause of top dying of sundri. Edaphic factors are related to the development top dying. Pathological factors have been found to aggravate the severity of the disorder in question. Salvage felling has been considered as a management tool for top dying of sundri. Suggestions for further studies are provided. INTRODUCTION Sundri (Heritiera fomes) has been suffering from a top dying disease syndrome in the Sundarbans. In general, top dying sundri trees have a dead and truncated top, accompanied with the death of twigs and branches to a varying degree, leaving a variable extent of healthy canopy. The disease syndrome is quite extensive in the Sundarbans and is considered to be the most serious of all diseases/ disorders of trees in Bangladesh. It is generally believed to be the result of a complex interaction of abiotic and biotic factors. A critical chronological review of literature on top dying of sundri has therefore been undertaken to find outthe stratus of knowledge and what further study is needed to be undertaken in future. 2. A Chronological Account of Top Dying of Sundri and Related Knowledge Troup (1921) noted that sundri trees growing in depressions tend to deteriorate rapidly and die off. Severe damage is caused periodically by cyclones, which uproot the trees, break the tops off, or tear off the branches. The severe cyclone of 1909 caused immense damage to sundri. Curtis (1933) found that the average diameter upto, which an average sundri tree remains sound and healthy, is estimated to be 33 cm, corresponding to an age of 131.5 years. This diameter may be termed as the mature diameter. Sundri trees beyond this size are very liable to develop cankers or become stag-headed. Similarly the corresponding mature diameter of average second qualrty sundri is estimated to be around 25 cm. Ahmed (1957) reported for compartments 30,31 and 32 an average of 3-17% uirsound (top dying) sundri trees were in the Sundarbans. He noted that production of greater opening in the canopy (through heavy thinning or logging) induce development of epicormic branches and render H. fomes vulnerable to cyclonic damage. This may indicate association between top dying of H. fomes and wind damage. Forestal (1960) recorded top dying ofsundri in the Sundarbans. Chowdhury (1968) noted cyclone torn crown of H. fomes and opined that it could provide passage to rot fungi. 1. Profl Dr. Mohammad Abdur Rahman, House # 25lA, Road # 2, Sector #,Uttara, Dhaka; 2. Professor, FWT Discipline, Khulna University, Khulna; & 3. Professor, trES, Chittagong University, Chittagong. 37