Effects of sand burial stress on the early developments of cyanobacterial crusts in the field

Sand burial is a noticeable environmental disturbance commonly experienced by various types of biological soil crusts (BSCs) composed of microorganisms. BSCs have been regarded as a feasible avenue to resist desertification in China. However, the cyanobacterial crusts, existing at early developmental stage of BSCs, are exceedingly susceptible to burial by sand. Therefore, a study campaign over 7-week was conducted in fields to evaluate the effects of sand burial (burial depth of 0, 0.5, 1, 3 and 5 cm) on the crusts in Hopq Desert, China. The results showed that sand burial imposed severe stress on the cyanobacteria crusts, such as the reduction of chlorophyll a, the restraint of scytonemin synthesis and the damage to PSII activity, as well as the decrease of total carbohydrate reserve. We discuss in this study possible mechanisms by which cyanobacterial crusts tolerate burial, and the positive role of rain in the recovery of cyanobacterial crusts from burial. It is necessary for the cyanobacterial crusts to allay burial disturbances in order to ensure their better contribution to desert reclamation. (C) 2011 Published by Elsevier Masson SAS.