Soil organic carbon and total nitrogen storage under different land uses in the Naiman Banner, a semiarid degraded region of northern China

Accurate investigation of soil organic carbon (SOC) and total nitrogen (TN) storage at a regional level is important for detecting changes in the C and N sequestration and emission potentials induced by land-use and cover type changes. In a degraded semiarid region of northern China's Horqin Sandy Land, we selected 208 locations and calculated SOC and TN storage to a depth of 100 cm for the main land-use and cover types. The productive cropland on former grassland had the highest level of SOC and TN storage (6613 g C m(-2) and 709 g N m(-2)). The corresponding storage values were 3758 g C m(-2) and 402 g N m(-2) in degraded grassland, 3449 g C m-(2) and 373 g N m(-2) in afforested dunes, 2674 g C m(-2) and 320 g N m(-2) in unproductive cropland on former dunes, and 1109 g C m(-2) and 129 g N m(-2) in sand dunes (from mobile to fixed). The average soil bulk density was highest in sand dunes, with a value of 1.59 g cm(-3), and lowest in productive cropland on former grassland, with a value of 1.39 g cm(-3). The conversion of severely degraded sandy land into other land-use and cover types therefore has considerable potential to partially offset the SOC and TN loss during the past century that has resulted from desertification in the Horqin Sandy Land.