Wind Erosion in Western Queensland Australia

Chapter 4 –Modelling Soil Erodibility Dynamics1998). In terms of sediment transport potential, Eldridge and Leys (2003) reported a 4-foldincrease in the streamwise sediment flux (Q, gm -1 s -1 at 65 kmh -1 ) for disturbed sandy soils(relative to the soil in a crusted condition), and a 26-fold increase in the streamwise sedimentflux of disturbed loamy soils. Accounting for temporal changes in soil erodibility in winderosion models is therefore critical for the accurate simulation of wind erosion processes.As identified in Chapter 3, few wind erosion modelling systems contain schemes to computetemporal changes in soil erodibility. Field measurements of aggregate size distributions andempirical expressions relating soil texture (sand, silt and clay content), organic matter (OM)and calcium carbonate (CaCO 3 ) content have been used to account for soil erodibility in somemodels (Chepil and Woodruff, 1954; Fryrear et al., 1998; Singh et al., 1999; Böhner et al.,2003). Fryrear et al. (1994) developed a model to compute the wind erodible fraction of soils(aggregates < 0.84 mm) using inputs of soil texture, OM and CaCO 3 . The model was adaptedby Hagen (1991) to simulate temporal changes in soil erodibility for the Wind ErosionPrediction System (Chapter 3). Global application of the WEPS soil erodibility predictionscheme has been limited by the low availability of input spatial data for the OM and CaCO 3model parameters, and the model applicability to soils outside North America (Leys et al.,1996). Established regional to global scale wind erosion models, such as the Dust ProductionModel (Marticorena and Bergametti, 1995), and Integrated Wind Erosion Modelling System(Lu and Shao, 2001) do not consider temporal changes in surface crusting or aggregation.This is due to the absence of soil erodibility models applicable at these scales, and yet issurprising given the dependence of global dust emissions on spatial and temporal variationsin soil erodibility (Grini et al., 2005).Building models to simulate temporal changes in soil erodibility is essential for thedevelopment of robust wind erosion modelling systems. In particular, this is of importance toincreasing the skill of models like AUSLEM in assessing land susceptibility to wind erosionin rangeland environments. This chapter has three aims that seek to address this issue. Thefirst is to draw on published research to develop a conceptual model of the soil erodibilitycontinuum. The second aim is to establish a framework for modelling temporal changes insoil erodibility that could be integrated into a revised AUSLEM (Chapter 5). The frameworkcharacterises the temporal response of soils subject to variable precipitation and disturbanceby livestock trampling that are dominant controls on soil erodibility in rangelandenvironments. The final aim is to use the model framework to highlight deficiencies in our101