Horizontal and vertical distribution of carbon stock in natural stands of Hyrcanian lowland forests: A case study, Nour Forest Park, Iran

Abstract

ABSTRACT:The Nour Forest Park located in the north of Iran is the most important Hyrcanian lowland forest which plays a significant role in the local/national carbon cycle. Since the forest is protectively managed, the distribution of C pools in the forest may give proper information for climate change negotiations. We investigated variations in above-and belowground C pools between three natural stand types that occur in the forest -Alnus glutinosa-Parrotia persica (AI), Acer velutinum-Parrotia persica (MI), and Ulmus glabra-Carpinus betulus (EH). The carbon stocks of trees, herbs and litter were measured in each stand based on a completely randomized design using nested plots. Soil organic carbon (SOC) stock was measured at two depths (0-20 and 20-40 cm). The mean organic carbon concentration of 20.61 ± 0.012% and of 31.13 ± 0.024% was directly measured for herbs and litter, respectively. The results of the paired t-test showed that there was no significant difference in SOC between the first depth (0-20 cm) and the second depth (20-40 cm) in AI stand though SOC was significantly different between the two depths in MI and EH stands. The carbon stock of above-and belowground biomass was not significantly different between the three stands, and carbon stock of litter was higher than that of herbs in each stand. Also, there were significant differences in the different carbon pools in each stand type; however, the different stand types did not differ in the proportion of carbon stored in different pools and in total carbon (i.e. C summed across all pools; P > 0.05). The findings in the different forest types showed that there was no high carbon stock variability suggesting that the horizontal and vertical distribution of carbon stocks in the forest could be in a balance, implying that the protective management could be a determining factor for the carbon balance in the forest. Regarding this issue, it is necessary to verify the variation of carbon stocks in non-protective and active forest management.