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Cryptobiotic crusts are a dominant component of an area of dunes and pans situated on Pleistocene Lake Thompson bed at Edwards Air Force Base (EAFB), California. Crusts cover about 50% of the surface area; upland crusts cover 80% of the dunes, aquatic remnant crusts cover about 20% of the pans. The biomass of the crusts is about twice the maximum reported elsewhere. As typical for cryptobiotic crust communities, the cyanophyte Microcoleus vaginatus dominated the upland crusts; however, neither mossnor lichen-dominated crusts were found. The pans present an enigma; some were dominated by cyanobacterial crusts-, while others were dominated by bacterial crusts. Both natural disturbance (e.g. mammal burrows) and anthropogenic disturbance (e.g. foot traffic) appeared to have a negative effect on both the upland and aquatic remnant crusts. (C) 2002 Elsevier Science Ltd.