Abstract:The Minqin Oasis is located in the northwest Hexi Corridor, and the northern, western, and eastern edges are surrounded by the Tengger and Badain Jaran Deserts. To manage sand and prevent sandstorms, large tracts of Haloxylon ammodendron plantations have previously been planted on fixed and semi-fixed sand dunes of the Minqin Oasis fringe. At present, many biological soil crusts have formed and are developing in the fixed woodland. To ascertain whether the formation and development of dune biological soil crust affects soil texture, nutrient contents, and microorganism populations, the woodland of H. ammodendron plantations were divided into a no crust stage (NCS), physical-algal crust stage (PACS), algal-lichen crust stage (ALCS), and lichen-moss crust stage (LMCS) according to crust coverage, crust thickness, and underlying and ground covers. Here, the contents of soil clay, silt, fine sand, and coarse sand particles, organic matter, total nitrogen, available phosphorus and potassium, and the populations or biomass of bacteria, fungi, and actinomycetes in the 0-1 cm soil layer were measured and studied. The results showed that 1) the formation and development of biological soil crusts from NCS to ALCS not only considerably increased the content of fine soil particles (0-200 μm) but also decreased soil coarse particle (200-2000 μm) contents. However, there was no significant change in soil particle composition during the succession from ALCS to LMCS; 2) the succession of biological soil crusts obviously influenced the contents of soil organic matter, total nitrogen, available phosphorus and potassium, and their contents gradually increased with succession; 3) during biological soil crust succession, all quantities of soil bacteria, fungi, and actinomycetes showed a trend of initially increasing and then decreasing, peaking in PACS. Simultaneously, the soil total algal biomass continuously increased. Furthermore, microbial quantities or biomass also presented a trend of initially increasing and then decreasing from May to December; and 4) in succession from NCS to PACS, the change of soil particle composition was one of the main factors causing variations in soil organic matter, total nitrogen, available phosphorus and potassium, bacteria, fungi, and actinomycetes. During succession from PACS to LMCS, soil algae, lichen, and mosses were the main factors improving soil organic matter, total nitrogen, and available phosphorus and potassium contents. It was suggested that the formation and development of the biological soil crust distributed in the surface layer soil of Minqin Oasis fringe dunes not only ameliorated shallow soil quality effectively, but also played a considerable role in improving soil ecosystems and protecting the ecological environment.