To estimate the aboveground biomass and carbon storage in multi-species plantations we used species-specific equations method and three other generic methods. Astara county is located in northern Iran. It has a total area of 1,757 ha. Based on species-specific allometric equations, total aboveground biomass was calculated andvaried between 81.13 and 98.21 t·ha^–1 for Acer velutinum, 68.36 and 83.44 t·ha^–1 for Quercus castanifolia, 71.88 and 119.22 t·ha^–1 for Tilia begonifolia, 56.07 and 61.98 t·ha^–1 for Fraxinus excelsior and from 37.92 to 51.34 t·ha^–1 for Prunus avium. There was a significant difference between the mean values of total aboveground biomass estimation obtained by species-specific equations and the three generic methods for Alnus subcordata, Pinus taeda and Pinus nigra. Results indicated that using generalized methods produced more reliable and accurate estimations for native species than for exotic species for rapid biomass and carbon estimation in order to decide on plantation development in the area.