Effects of afforestation on soil organic carbon and other soil properties

Abstract

Soil organic carbon (SOC) makes up a significant portion of the worlds terrestrial carbon stocks, and changes in land-use and land cover are changing soil carbon stocks. This study investigated the effects on soil organic carbon and some other soil properties of afforestation efforts using 15-year-old Pinus nigra Arn. Subsp. nigra (Black Pine) and Cedrus libani A. Rich (Lebanon cedar) on bare land in the semi-arid Nigde Akkaya dam watershed for erosion control and green belt creation. Soil samples were collected from three land use types (Black Pine planted, Lebanon cedar planted area and bare land) at two soil depths (0–10cm and 10–20cm) and replicated three times. Among the soil properties substantially affected by the change in land cover are soil organic carbon, bulk density, particle density, water holding capacity and total porosity. Generally, soil organic carbon was observed to increase after afforestation. Soil organic carbon (SOC) values were 1.09% and 1.13% in Black Pine and the Cedar area, respectively. These values were significantly higher than the values for the bare land soils (0.54%). For all types of land use, the amount of SOC in the soils decreased with depth. The amount of carbon sequestrated in Black Pine, Cedar and bare land sites at depths of 0–10cm and 10–20cm were 18.20t/ha and 16.33t/ha, 23.54t/ha and 12.38t/ha and 11.2t/ha and 7.22t/ha, respectively. The bulk density values obtained from the 0–10cm layer soils in the afforested lands (1.53g/cm3 for Black Pine and 1.58g/cm3 for Cedar) were different from and lower than those in bare land (1.75g/cm3). Afforestation efforts led to an increase in water holding capacity (WHC) of the soil. Total porosity (TP) of the 0–10cm layer soils increased after afforestation. This study indicated that on degraded land in a semiarid region, afforestation increased soil carbon sequestration, improved some soil properties and reduced erosion over a 15-year period.