Distribution of soil organic carbon impacted by land-use changes in a hilly watershed of the Loess Plateau, China.

Vegetation restoration, terrace and check dam construction are the major measures for soil and water conservation on the Loess Plateau. These effective measures of stabilizing soils have significant impacts on soil organic carbon (SOC) distribution. However, following ecological construction, whether the hilly watershed acts as a source or a sink of soil carbon is still unknown. To understand the impact of land-use changes combined with check dam construction on SOC distribution, 1060 soil samples were collected from a 100 cm soil profile across a watershed on the Loess Plateau. The soils in the 0-20 cm layer had a higher SOC concentration than those of the 20-40, 40-60, 60-80 and 80-100 cm layers. Forestland, shrubland and terrace had significant higher SOC concentrations in the 0-20 cm soil layer than that of sloping cropland and dammed farmland (p < 0.05). SOC densities (0-100 cm) in terrace, forestland, shrubland, grassland, sloping cropland and dammed farmland were 12.09, 11.99, 11.89, 11.77, 11.41 and 10.11 kg m-2, respectively. These estimations suggested that SOC was redistributed in the watershed through land-use changes. Topographical factors, including altitude, aspect and slope had impacts on SOC concentrations. The application of hydrological controls to hillslopes and along river channels should be considered when assessing carbon sequestration within the soil erosion subsystem.