Abstract:The soil of 0—20 and 20—40 cm layers under different vegetations along an elevation gradient of Helan Mountains were investigated. We analyzed the variation characteristics of aggregate content of different particle sizes and aggregate stability with the increasing elevation, and explored the correlation between soil physicochemical properties and aggregate stability.The results showed that 0.25~0.053 mm aggregates were the main aggregates in 0—20 cm soil layer. With the increases in elevation, the contents of water-stable macroaggregates (>0.25 mm) increased, and the contents of <0.053 mm aggregates decreased, indicating that the soil aggregates changed from small particle size to large aggregates with the increasing elevation.In the 20—40 cm soil layer, the contents of water-stable macroaggregates reached the highest at mid-elevation (2 139 m), which was 65.73%. The mean weight diameter (MWD) and geometric mean diameter (GMD) at both 0—20 and 20—40 cm soil layers increased first and then decreased with the increasing elevation, with the peak value at 2 139 m.The MWD and GMD of soil aggregates in different elevation gradients were positively correlated with soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), silt and sand content, and negatively correlated with clay content and pH. These results suggestted that the overall stability of soil aggregates along the elevations of Helan Mountains were ranked as medium elevations>high altitude>low altitude. Higher content of macroaggregates and soil nutrients contributed to the stability of aggregates.