of Arizona, involving denudation by a destructive fireindicated that whereas erosion losses before the firewere only 43 tonnes per square kilometer per yearafter the fire they were between 50,000 and 150,000tonnes per square kilometer per year. The causes othe marked erosion associated with chaparral burningare particularly interesting. There is normally a distinctive ‘non-wettable’ layer in the soils supportingchaparral. This layer, composed of soil particles coatedby hydrophobic substances leached from the shrubsor their litter, is normally associated with the upperpart of the soil profile (Mooney and Parsons, 1973)and builds up through time in the unburned chaparralThe high temperatures that accompany chaparral firescause these hydrophobic substances to be distilled sothat they condense on lower soil layers. This processresults in a shallow layer of wettable soil overlying anon-wettable layer. Such a condition, especially on steepslopes, can result in severe surface erosion (DeBano2000; Shakesby et al., 2000; Letey, 2001).
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