The pattern of soil carbon sequestration changes regarding physico-chemical soil properties (Case study: Semnan Sokan forest park)

This study was carried out to model the soil carbon sequestration changes regarding to soil physical and chemical properties in pure and mixed stands of Eldar pine (Pinus eldarica Medw.) and black locust (Robinia pseudoacacia L.) planted in Semnan Sokan forest park. Four different treatments including pure Eldar pine, pure black locust, mixed of these species and control (without any plant cover) were considered. Soil samples were taken from different soil depth (0-5, 5-10, 10-20, and 20-30 cm) in the treatments and transported to laboratory for further analysis. The results showed that the Eldar pine trees decreased soil acidity and increased aggregates stability of soil. Black locust increased organic matter content, phosphorus, potassium, and nitrogen content of soil which can improve the quality of poor soils of this area. The mixed treatments affect soil properties partly between two above mentioned treatments. The carbon sequestration for Robinia, Pine, mixed and control treatments were 28.67, 18.74, 24.05 and 1.73 tons per hectare, respectively.The modeling of carbon sequestration with physical and chemical properties of soil, the nitrogen and phosphorus were determined as the most important effecting factors on the soil carbon sequestration. Therefore, increasing soil nitrogen in such regions via biological methods (planting nitrogen fixing plants) can play important role in success of afforestion and carbon sequestration projects in such regions.