The paper investigated the distribution regularity of organic carbon contents in different soil layers of 3, 9, 13 and 17-year agro-forestry intercropping systems and 5, 10 and 15-year Farmland Shelterbelt Nets systems, and at the same time, analyzed the correlation among the characteristics of organic carbon, soil pH value and total N for a further study. The results demonstrate that in the vertical direction, the organic carbon content decreases as the soil depth increases and at the temporal scale, it increases as the number of year for inte...