Growth density and regeneration of afforested mangroves at Mirersarai forest range in Bangladesh

Abstract

The aim of the study was to determine growth performance of planted mangroves at three beats of Mirersarai forest range in the Chittagong coastal afforestation division, Bangladesh. This 22–29-year-old mangrove plantation showed satisfactory growth and regeneration with variations among different study sites. The study revealed that individual species density and overall density (stem/ha) in the study sites varied significantly (p ≤ 0.05) where density of Sonneratia apetala was maximum among five species followed by Excoecaria agallocha, Avicennia officinalis, Ceriops decandra and Bruguiera sexangula. Sonneratia apetala attained the highest mean diameter at breast height (DBH) (cm) and height (m) among all the plantation species. It was found dominant at the middle section plantations of three beats, whereas Bruguiera sexangula and Ceriops decandra were found absent at seaside plantation sites. Overall tree density was found to be highest at the middle part (1880 stem/ha) followed by inland (1610 stem/ha) and seaside (1087 stem/ha) plantations. Mean annual increment of height and of DBH were significantly higher for Sonneratia apetala (0.42 m/year, 0.81 cm/year) followed by Avicennia officinalis (0.32 m/year, 0.67 cm/year), Bruguiera sexangula (0.18 m/year, 0.40 cm/year), Excoecaria agallocha (0.16 m/year, 0.30 cm/year) and Ceriops decandra (0.05 m/year, 0.10 cm/year), respectively. Regeneration of vegetations showed promising performance in three beats. Sonneratia apetala showed rich regeneration at seaside plantations than inner parts in northern beats than those of southern beats. For all beats this species has an increased regeneration from inland to seaside plantation strips. Avicennia officinalis seedlings were found highest at the middle part of the plantation, whereas Excoecaria agallocha was found to be regenerated with high density at the inland part with a decreasing trend toward seaside strips. However, Bruguiera sexangula was found to be regenerated only at inland strips. Thus, this suggests that a coastal afforestation program with different species will show varied growth, regeneration and density at different situations according to species ecology and adaptability to the sites along the coast .