INFLUENCE OF CRYPTOGAMIC CRUST DISTURBANCE TO WIND EROSION ON SAND AND LOAM RANGELAND SOILS

A portable field wind tunnel was used to assess the sediment flux rate s of loam and sand textured soils in the Mallee region of southeastern Australia. Three levels of crust disturbance (nil, moderate and sever e) simulating stock trampling were investigated. The results demonstra ted the importance of cryptogamic crusts in binding the soil surface a nd providing roughness after the soil was moderately disturbed. On the loamy soil, the crust helped maintain sediment flux rates below the e rosion control target to 5 g m(-1) s(-1) for a 65 km h(-1) wind measur ed at 10 m height. Once the crust was severely disturbed, sediment flu xes increased to 1.6 times the erosion target. On the sandy soil, even with no crust disturbance the sediment flux was 1.6 times the erosion control target. Disturbing the crust increased sediment fluxes to a m aximum of 6.7 times the erosion control target. Removal of the crust a lso decreased the threshold wind velocity that resulted in an increase to the risk of erosion from <5 per cent to 20 per cent. (C) 1998 John Wiley & Sons, Ltd.