Abstract: Fifteen indicators of soil physicochemical properties, enzyme activity and microbial quantity were measured in a space-time substitution experiment, to characterize the changes in soil properties in nebkhas formed in association with Tamarix ramosissima within the transition zone from oasis to desert in the Minqin Lake region. With increasing degradation, bulk density increased, organic matter and cation exchange capacity increased in the early stages, and later decreased; soil moisture, total salt content, and electric conductivity decreased, while pH remained unchanged. The pattern of change in the profile with increasing soil depth was that bulk density increased, while soil moisture content, organic matter, and cation exchange capacity decreased, while total salt content and electrical conductivity were highest in the 5-10 cm soil layer. The abundance of soil microorganisms, and soil enzyme activity decreased with increase in degradation status and with soil depth. All soil physicochemical properties and soil biological characteristics, except individual index, showed statistically significant differences,while the relationship between degenerative state or soil depth needs to be researched. In conclusion, the soil physicochemical properties and biological characteristics were adversely affected in the degraded nebkhas. Therefore, vegetation and soil factors should be considered together when planning restoration of degraded nebkhas.

Key words: Tamarix ramosissima nebkhas, degradation, physicochemical properties, biological characteristics