Wind Erosion in Western Queensland Australia

Chapter 2 – Land Erodibility Controlsdisturbance, season, antecedent climatic conditions and the state of a crusted surface at thetime of disturbance are vital in determining the level of crust degradation suffered with aparticular disturbance mechanism (Marble and Harper, 1989; Scarlett, 1994). Spatio-temporalvariability in climate and disturbance regimes leads to variable and spatially heterogeneousphysical and biological crust cover in many landscapes. Transitions between physical andbiological crust types may result from disturbance-recovery cycles, and this has implicationswind erosion processes (Strong, 2007).Soil crust characteristics that influence soil susceptibility to wind erosion include cover,structure (arrangement of particles by grain size), thickness, strength, and modulus of rupture(resistance to breaking by saltating particles). Spatial heterogeneity in these characteristics,combined with disturbance mechanisms also affects the crust influence on wind erosion.Crust Effects on Wind ErosionSoil crusts reduce soil erodibility by binding soil particles (locking them into a non-erodiblesurface layer), reducing the availability of loose erodible sediment, and increasing surfaceroughness. Thick surface crusts with a high modulus of rupture can provide a non-erodiblearmour over a surface.In general, an increase in surface crust cover and strength results in an overall decrease in soilerodibility. Chepil (1942) reported that crusted soils may erode at a rate about one-sixth thatof non-crusted soils. This relationship was later determined to be more complex. Leys andEldridge (1998) reported crust effects on wind erosion under three levels of simulateddisturbance on a range of soil textures. They found that on the sandy soils, erosion rates werestatistically the same under the three disturbance levels; however, for the loamy soils therewas a significant increase in erosion rate with increasing disturbance. Rajot et al. (2003)reported a 75% decrease in loose erodible particles on the soil surface due to crust formationfollowing rain. Various other studies have reported the effects of soil properties on crustformation and its effects on wind erosion (e.g. Belnap and Gillette, 1997, 1998; Goosens,2004; Langston and McKenna-Neuman, 2005; Thomas and Dougill, 2007). In general thesestudies have examined the effects of disturbance (i.e. by livestock or mechanical processes)on crust cover and erosion rates.52