Study on the effects of land use change in low yield drylands to agro-forestry on soil physical properties and organic carbon stock

Human caused major impacts on formation and development of soil by management operations including change in land cover and use. This research was conducted to evaluate the land use change and management operation type on qualitative and quantitative properties of soil organic carbon. For this means, land use changes of drylands to agro-forestry compared with other crop management operation types including legume-cereal rotation type with medium and intensive tillage system and straw burning. Results indicated that free light fraction and inter aggregate light fraction organic carbon in agro-forestry land use type was doubled and 10 folded compared with semi intended tillage with legumes in rotation system and intensive tillage with straw burning farms, respectively. Course particulate organic carbon, fine particulate organic carbon and carbon associate with silt and clay in agro-forestry land use type was 3.7, 4.6 and 22 gr/kg soil, respectively. Also, amounts of these carbon fractions in miss management drylands were 0.2, 0.3 and 4 gr/kg soil, respectively. Thus, land use change from dryland, especially, low yield dryland, to agro-forestry, while maintaining and enhancing soil organic carbon stocks, can increased return period and degradation intensity of carbon stock and resulted to longer time of emission of carbon into the atmosphere. This can improve the atmosphere and biosphere carbon balance useful for climate change mitigation.