Abstract: Taking the Didymodon vinealis (Brid.) Zand crust from an artificial vegetation area of Shapotou Desert Research and Experiment Station in Northwest China as test object, a 10-daylaboratory simulation experiment was conducted to study the effects of enhanced UVB on the physiological metabolism and photosystemrelated protein expression of the crust. Four UV-B treatments were installed, i.e., 2.75 (CK), 3.08, 3.25 and 3.41 W·m^-2. With the increasing UV-B radiation, the malondialdehyde (MDA) content presented an increasing trend, while the chlorophyll a fluorescenceinduced kinetics parameters and the watersoluble protein and thylakoid membrane proteins expression showed a continuous decrease, and the decrement was negatively proportional to the intensity of the UV-B radiation. The enhanced UV-B radiation accelerated the reactive oxygen species (ROS) metabolism rate, induced the lipid peroxidation, decreased the watersoluble protein content, and further, reduced the activity of the reaction center of photosystem II (PSII), leading to the decline of photosynthesis. This study would help us to further understand the response mechanisms of biological soil crust (BSC) under UV-B radiation, and have academic and practical significances for the BSC application in
desertification areas.

Key words: ecological stoichiometry, marine plankton, biogeochemical cycles,  , growth rate,  food web.