Intact soil monoliths with surfaces of varying microphytic crust cover were
collected from a calcareous earth soil in a semi-arid belah–rosewood
woodland near Wentworth in south-western New South Wales. Monoliths were
tested for their susceptibility to erosion by rain-impacted flow using a
laboratory rainfall simulator. The erosive stress applied to 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 raindrops falling 11·2
m at average rainfall intensities of 65 mm/h. Increasing the cover of
microphytic crusts on the surface resulted in a significant
(P = 0·001) reduction in sediment
concentration. A linear model incorporating percentage cover and distribution
of cover accounted for 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 4-mm depth. Management practices such as overgrazing,
trampling, and fire, which reduce the cover of crusts in this landscape, will
lead to increased erosion hazard.
