Microbial biomass carbon (MBC) is an important component of soil organic carbon and an important indicator of degraded ecosystem restoration assessment. To understand how biological soil crusts affect soil MBC content in the southeastern edge of the Tengger Desert, China, sandy soil under different types of biological soil crusts was sampled at artificially stabilized sand dunes, and sandy soil at mobile sand dunes was also sampled as the contrast. The sampling plots at the artificially stabilized sand dunes were distributed in four areas with different sand-fixing time (the sand dune were stabilized in 1956, 1964, 1981 and 1987, respectively). Compared with the contrast in the mobile sand dunes, Bryum argenteum crust and algae crust could significantly increase the content of soil MBC in the 54-year-old, 46-year-old, 29-year-old and 23-year-old stabilized sand dunes(P<0.05). Soil MBC content under crusts is positively correlated with the sand dune fixation time ( P<0.05). Bryum argenteum and algae crusts could significantly increase the content of MBC at 0-20 cm soil layer. However, the effect decreases gradually as soil depth increases and no significant difference is showed at 20-30 cm soil layer (P＞0.05). Therefore, disturbances to biological soil crusts may lead to the loss of soil MBC.

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