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 rates of loam and sand textured soils in the Mallee region of southeastern Australia. Three levels of crust disturbance (nil, moderate and severe) simulating stock trampling were investigated. The results demonstrated the importance of cryptogamic crusts in binding the soil surface and providing roughness after the soil was moderately disturbed. On the loamy soil, the crust helped maintain sediment flux rates below the erosion control target to 5 g m(-1) s(-1) for a 65 km h(-1) wind measured at 10 m height. Once the crust was severely disturbed, sediment fluxes 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 maximum of 6.7 times the erosion control target. Removal of the crust also 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.