Effects of apple orchard converted from cropland on C and N storages in terrestrial system of slopping cultivated land in the Loess Gully Regions

Land use change plays an important role in organic carbon and total nitrogen storage in a terrestrial system. To better understanding the mechanism of organic carbon in the terrestrial system, soil organic carbon (SOC), total nitrogen (TN) in 0100cm soil layer, aboveground and belowground biomasses of apple trees were studied in a 20- year of apple orchard converted from croplands, and the effects of converting cropland to apple orchard on carbon and total N storage were evaluated in a terrestrial system in slopping cultivated land of the Loess Gully region. The results show that the SOC storage in 0100 cm soil in the apple orchard is C 50.7 Mg/ha, which is lower than that in the cropland. For topsoil (020cm), SOC storage in the apple orchard is increased by 9.2% compared to the cropland, while for subsoil (20100cm), SOC storage in the cropland is more than that in the apple orchard. Total N in 0100cm soil layer of the apple orchard is lower than that in the cropland (p 0.05). Carbon and nitrogen storages in aboveground and root of apple trees are 5.8 and 1.7 times of the crop plants after the 20 year conversion of cropland to apple orchard in the sloping cultivated land. The apple tree stem, branch and root contribute much to the changes in C and N storages in the terrestrial system