Study on soil microbiotic crust and its influences on sand-fixing vegetation in arid desert region

Based on secular fared-site data in the artificial sand-fixing vegetation district at the southeast fringe of the Tengger Desert, the formative characteristics of soil microbiotic crusts and its influences on vegetation dynamics were analyzed. Once sand barrier and artificial vegetation have stabilized the surface of the sifting sand, could form aeolian deposition crust and then evolve into algae-dominated crust. Such processes result from the interactions of physical effects of atmospheric dust and silt deposition on sand surface, sinking and raindrop impact, and soil microorganism activities. Under the condition of less than 200 mm precipitation, the presence of microbiotic crust changes the soil hydraulic conductivity, alters the temporal and spatial distribution of the limited precipitation in sand layer and leads to the decline of deep-rooted shrubs. The development of microbiotic crust and subsurface soil affects the plant growth and seed rain distribution, as a result, the diversity of plant species gradually tend to become saturated and finally affects the vegetation stability.