ASSESSMENT OF EROSION RATES FROM MICROPHYTE-DOMINATED CALCAREOUS SOILS UNDER RAIN-IMPACTED FLOW

Intact soil monoliths with surfaces of varying microphytic crust cover were collected from a calcareous earth soil in a semi-arid belah-rose wood woodland near Wentworth in south-western New South Wales. Monolit hs were tested for their susceptibility to erosion by rain-impacted fl ow using a laboratory rainfall simulator. The erosive stress applied t o each surface was controlled by varying the flow depth between 4 and 8 mm whilst maintaining a flow velocity of 25 mm/s using 2.7 mm raindr ops falling 11.2 m at average rainfall intensities of 65 mm/h. Increas ing the cover of microphytic crusts on the surface resulted in a signi ficant (P = 0.001) reduction in sediment concentration. A linear model incorporating percentage cover and distribution of cover accounted fo r 46% of the variance in soil erosion. A significant relationship was also found between the coarse fraction (>0.053 mm) and crust cover (P = 0.012) at the dmm depth. Management practices such as overgrazing, t rampling, and fire, which reduce the cover of crusts in this landscape , will lead to increased erosion hazard.