The study of biomass and carbon in mangrove forests is often performed by allometry methods. The allometry models in Mangrove trees are influenced by factors such as species, ecological conditions, and tree age. To study the allometry equation of hara shrub (Avicennia marina) in the Nayband Bay, a complete shrub of Hara from the mentioned area was picked up at 6 stations, and biometry, biomass, and carbon content of the samples were measured. According to the results, the best model for estimating the biomass in mangrove shrubs in Nayband is the power equation using a stem diameter at 30 cm height (ABG = 139.3d301.263). The ratio of the root to the top part (leaf and trunk) is 24%. According to the content of carbon in the biomass samples, the amount of carbon was 42% of the upper part biomass and 39% of the root biomass. The obtained allometry equation in this study is different from mature Avicennia marina in different parts of the world and Iran.
