Soil organic carbon and total nitrogen as affected by vegetation types in Northern Loess Plateau of China

One of the most fragile areas in the China Loess Plateau, is the transitional belt that is subjected to wind and water erosion. The transitional belt accounts for about 30% of the Loess Plateau area. To reduce soil degradation in the Loess Plateau, the Chinese government initiated a state-funded vegetation restoration project in 1999. The effectiveness of this project on transitional belt soils is unknown. The objective of this study is to determine the effects of four dominant vegetation types on soil organic carbon (SOC) and nitrogen (N) in a selected catchment within the transitional belt. Korshinsk Peashrub (KOP), purple alfalfa (ALF). and natural fallow (NAF) were selected as vegetation restoration types because they have been used widely to remedy soil degradation. The fourth vegetation type selected was millet (MIL) because it has been an important crop in the region. In 2004, four 61 x 5 m plots were established on 12 degrees slope land. The plots were parallel and separated by 80 cm. Based upon soil samples collected in August of 2007, there were large variations in the distributions and stocks of SOC and N across the four vegetation types. Compared with MIL, KOP significantly increased the concentration and stock of SOC and total nitrogen (TN) in 0-100 cm soil profiles, while ALF and NAF were not significantly different. The distributions of SOC and TIN concentrations and stocks of KOP, ALF and NAF were relatively uniform along a hillslope, while there was an increasing trend along the hillslope in MIL This result suggests that ALF and NAF would be beneficial in SOC and TN sequestration over a long-term because of their ability to reduce the loss of SOC and TN by soil erosion. We also found that both vegetation types and hillslope position had no significant effects on C:N ratio. Our Study demonstrated that improvements of SOC and TN stocks in the transitional belt could be made through well managed vegetation restoration measures. (C) 2009 Published by Elsevier B.V