Impact of deforestation on soil carbon stock and its spatial distribution in the Western Black Sea Region of Turkey

•Impact of land use change on carbon stock is investigated.•Land use change has a significant impact on carbon content in the uppermost soil.•Soil carbon and bulk density are negatively correlated.•Differences in carbon stock in forest and agricultural soils were statistically insignificant.•A conditional kriging approach is proposed to map the soil carbon stock.

Land use management is one of the most critical factors influencing soil carbon storage and the global carbon cycle. This study evaluates the impact of land use change on the soil carbon stock in the Karasu region of Turkey which in the last two decades has undergone substantial deforestation to expand hazelnut plantations. Analysis of seasonal soil data indicated that the carbon content decreased rapidly with depth for both land uses. Statistical analyses indicated that the difference between the surface carbon stock (defined over 0–5 cm depth) in agricultural and forested areas is statistically significant (Agricultural = 1.74 kg/m2, Forested = 2.09 kg/m2, p = 0.014). On the other hand, the average carbon stocks estimated over the 0–1 m depth were 12.36 and 12.12 kg/m2 in forested and agricultural soils, respectively. The carbon stock (defined over 1 m depth) in the two land uses were not significantly different which is attributed in part to the negative correlation between carbon stock and bulk density (−0.353, p < 0.01). The soil carbon stock over the entire study area was mapped using a conditional kriging approach which jointly uses the collected soil carbon data and satellite-based land use images. Based on the kriging map, the spatially soil carbon stock (0–1 m dept) ranged about 2 kg/m2 in highly developed areas to more than 23 kg/m2 in intensively cultivated areas as well as the averaged soil carbon stock (0–1 m depth) was estimated as 10.4 kg/m2.