Variation within soil organic carbon pool in the forest-paddy field edges (Case study: Nour Forest Park)

Soil organic carbon pools (SOCP) in forests play important roles in terms of biomass productivity level as well as mitigating the climate change effects. Land-use changes cause a potential loss of SOCPs in the forest. Hence, variation of SOCPs around the forest-paddy field transition zone in northern Iran was the main aim of this study. The study was conducted within the natural forest park forest of Nour in Mazandaran province, in which the weak drainage and long periods of soil waterlogging during the rainy season are considered as crucial threats. In two remnant forest fragments with similar stand type (Maple-Ironwood), extend (10 ha) and location (adjacent to the paddy fields), soil samples were collected from two depths of 0- 20 and 20-40 cm at five distances from the farm edge into the inner forest (10 m in the paddy field and 0–10, 30–40, 70–80 and 100–110 m towards the forest interior). All the samples were collected near to the dominant Acer velutinum trees, with a minimum distance of 10 m to each other. In addition, light intensity was measured based on v per m2 in the growing season by photo-light meter measuring device in constant vertical distance from the ground. The result of paired t-test showed significantly higher carbon budget in upper soil depth compared to the lower depth in both forest and paddy fields (P < 0.01). The result of one-way ANOVA indicated no significant differences among different distances to the forest stands (P>0.05). Surprisingly we observed no significant difference between the SOCPs in forest and paddy field. Besides, a significant inverse Pearson’s correlation between light intensity and SOCP was only observed for the upper soil depth in forest and paddy field (r=-0.37, P < 0.05).