Allometry, above-ground biomass and nutrient distribution in Ceriops decandra (Griffith) Ding Hou dominated forest types of the Sundarbans mangrove forest, Bangladesh

The Sundarbans, the world’s largest single expanse of natural mangroves located in southern Bangladesh, is the most productive mangrove ecosystem in the world. Ceriops decandra (Griff.) Ding Hou is the dominant shrub in the strong saline zone of the Sundarbans and is mainly extracted for fuel wood, charcoal and tannin. The harvest of C. decandra has decreased by about 50 % in the Sundarbans during the last 10 years creating a major concern. This study derived allometric models of above-ground biomass and estimated of above-ground standing and harvestable biomass and nutrient stock in C. decandra in dominant forest types (C. decandra and C. decandra–Excoecaria agallocha) in the Sundarbans. Allometric relationships between collar girth (CG) and biomass of plant parts (leaf, branch and stem) were tested using linear, power and logarithmic equations. The power equation was found to be most suitable. The density and the estimated total aboveground biomass of C. decandra in C. decandra and C. decandra–E. agallocha forest types were 33,237 and 965 stems/ha (density) and 33.49 and 14.36 t/ha (biomass), respectively. Also, 13.56 and 6.61 t/ha of harvestable biomass were estimated, from C. decandra and C. decandra–E. agallocha forest types, respectively. Nitrogen, potassium and phosphorus concentrations in the leaves, branches and stems showed significant (p < 0.05) variation. The findings of the present study will help to quantify the impact of present harvesting techniques and alteration of different silvicultural intervention like fixation of felling cycle, felling criterion, and regeneration and slash treatment.