Infiltration through three contrasting biological soil crusts in patterned landscapes in the Negev, Israel

We examined the role of soil crusts in infiltration processes in three contrasting environments in thc Northern, Central, and Central-Western Negev, Israel. The removal of a thin cyanobacterial-dominant crust from a sandy dune at Nizzana in the Central-Western Negev and of a well-developed lichen-dominant and a cyanobacterial-dominant crust from a loess-covered hillslope at Sayeret Shaked in the Northern Negev resulted in three to fivefold increases in sorptivity and steady-state infiltration under both pending and tension. The removal of a depositional crust colonised by cyanobacteria from a loess floodplain at Sede Zin in the Central Negev resulted in an increased infiltration under tension, bur had no significant effect under pending. We attribute the lack of effect under pending to exposure of surface silts to water, which resulted in the clogging of matrix pores and surface sealing. The removal of the crusts in all three landscapes influences resource flows, particularly the redistribution of runoff water, which is essential for the maintenance of desert soil surface patterning. It would also have marked effects on germination, establishment and survival of vascular plants and soil biota, leading ultimately to desertification. (C) 2000 Elsevier Science B.V. All rights reserved.