Wind Erosion in Western Queensland Australia

Chapter 2 – Land Erodibility Controlsspatial distribution of its controls within a landscape. If a landscape is modified as a result ofhuman activity, or natural disturbance processes such as fire, it may move over somethreshold, resulting in a non-linear increase in its susceptibility to wind erosion. The way inwhich landscapes are modified by human activities is largely dependent on land use. Landuses commonly associated with wind erosion are cultivation and pastoralism. Themanagement of landscapes under these land uses is quite different, and so the implications ofthese on wind erosion processes also differ.In cultivated lands there are often distinct boundaries between areas with particular landsurface conditions. The effects of land management on land erodibility in cultivatedenvironments are primarily seen through: 1) control of vegetation cover (crops); 2) control offield length (fetch); 3) control of soil aggregation and surface roughness through cultivation;and 4) control of soil moisture conditions through irrigation. While climate variability plays asignificant role in driving the state of these conditions, intensive management will oftenaffect the spatial distribution of erodible land areas (e.g. the location of fallowed fields) andthe timing of changes in controls (Leys, 1999).In rangelands, spatial and temporal changes in land erodibility are affected by climaticconditions and grazing pressures. Again, these affect spatial and temporal patterns invegetation cover, moisture and soil erodibility. Boundaries of management in rangelands mayappear to be less structured than in cultivated environments. However the effects ofvegetation consumption by grazing animals and trampling of the soil surface can vary fromcreating localised patches of highly erodible land to regional scale increases in erodibility.Spatial variability in grazing pressures may lead to the formation of wind erosion ‘hot spots’that are often significant dust emitters (Gillette, 1999).2.4 Conceptual Model of Land ErodibilityThis section provides a synthesis of the systems analysis presented in Section 2.2. Itsummarises the effects of controls on soil and land erodibility and combines these in aconceptual model of the land erodibility continuum.62