Effect of reforestation by broadleaf and coniferous species on aggregate stability and soil carbon sequestration in the Rimaleh, Khorramabad, Iran.
This study investigated the effects of reforestation by native broadleaf and exotic coniferous species on some soil properties at Rimaleh plantations, Khorramabad County, Iran. The experiment was performed by using a completely randomized design with Arizona cypress (Cupressus arizonica Greene), Turkish pine (Pinus brutia Ten.), wild almond (Amygdalus scoparia Spach) and control treatments in four replications. Each replication consisted of a 20 20 m2 plot. Diameter at breast height, canopy cover, and tree height were measured at each plot. Two combined soil specimens were sampled at the two distinct 0-10, and 10-20 cm depths in each treatment replication. The two-way ANOVA was used to compare the ratio of aggregate size and sand proportion, fractal dimension, the mean weight diameter (MWD) of aggregates, geometric mean diameter (GMD) of aggregates, and carbon sequestration among tree species and sampling depths. Results showed that wild almond and Turkish pine plantations play a major role in the development and sustainability of both coarse (more than 2000 µm) and fine (less than 53 µm) aggregates. The Arizona cypress plantations only led to increase of fine aggregates (53-250 and less than 53 µm). A significant increase also was observed in the MWD and GMD of aggregates, and the carbon sequestration in the wild almond plantation soil. In a short time, the wild almond and Turkish pine plantations added more organic carbon to the soil and improved both the soil properties and the stability of aggregates in comparison to the Arizona cypress and control treatment.