Grazing impacts on the susceptibility of rangelands to wind erosion: The effects of stocking rate, stocking strategy and land condition

An estimated 110 Mt of dust is eroded by wind from the Australian land surface each year, most of which originates from the arid and semi-arid rangelands. Livestock production is thought to increase the susceptibility of the rangelands to wind erosion by reducing vegetation cover and modifying surface soil stability. However, research is yet to quantify the impacts of grazing land management on the erodibility of the Australian rangelands, or determine how these impacts vary among land types and over time. We present a simulation analysis that links a pasture growth and animal production model (GRASP) to the Australian Land Erodibility Model (AUSLEM) to evaluate the impacts of stocking rate, stocking strategy and land condition on the erodibility of four land types in western Queensland, Australia. Our results show that declining land condition, over stocking, and using inflexible stocking strategies have potential to increase land erodibility and amplify accelerated soil erosion. However, land erodibility responses to grazing are complex and influenced by land type sensitivities to different grazing strategies and local climate characteristics. Our simulations show that land types which are more resilient to livestock grazing tend to be least susceptible to accelerated wind erosion. Increases in land erodibility are found to occur most often during climatic transitions when vegetation cover is most sensitive to grazing pressure. However, grazing effects are limited during extreme wet and dry periods when the influence of climate on vegetation cover is strongest. Our research provides the opportunity to estimate the effects of different land management practices across a range of land types, and provides a better understanding of the mechanisms of accelerated erosion resulting from pastoral activities. The approach could help further assessment of land erodibility at a broader scale notably if combined with wind erosion models

Grazing impacts on the susceptibility of rangelands to wind erosion: The effects of stocking rate, stocking strategy and land condition

An estimated 110 Mt of dust is eroded by wind from the Australian land surface each year, most of which originates from the arid and semi-arid rangelands. Livestock production is thought to increase the susceptibility of the rangelands to wind erosion by reducing vegetation cover and modifying surface soil stability. However, research is yet to quantify the impacts of grazing land management on the erodibility of the Australian rangelands, or determine how these impacts vary among land types and over time. We present a simulation analysis that links a pasture growth and animal production model (GRASP) to the Australian Land Erodibility Model (AUSLEM) to evaluate the impacts of stocking rate, stocking strategy and land condition on the erodibility of four land types in western Queensland, Australia. Our results show that declining land condition, over stocking, and using inflexible stocking strategies have potential to increase land erodibility and amplify accelerated soil erosion. However, land erodibility responses to grazing are complex and influenced by land type sensitivities to different grazing strategies and local climate characteristics. Our simulations show that land types which are more resilient to livestock grazing tend to be least susceptible to accelerated wind erosion. Increases in land erodibility are found to occur most often during climatic transitions when vegetation cover is most sensitive to grazing pressure. However, grazing effects are limited during extreme wet and dry periods when the influence of climate on vegetation cover is strongest. Our research provides the opportunity to estimate the effects of different land management practices across a range of land types, and provides a better understanding of the mechanisms of accelerated erosion resulting from pastoral activities. The approach could help further assessment of land erodibility at a broader scale notably if combined with wind erosion models

Development and testing of a micro wind tunnel for on-site wind erosion simulations

Wind erosion processes affect soil surfaces across all land uses worldwide. Understanding the spatial and temporal scales of wind erosion is a challenging undertaking because these processes are diverse and highly variable. Wind tunnels provide a useful tool as they can be used to simulate erosion at small spatial scales. Portable wind tunnels are particularly valued because erosion can be simulated on undisturbed soil surfaces in the field. There has been a long history of use of large portable wind tunnels, with consensus that these wind erosion simulation tools can meet real world aerodynamic criteria. However, one consequence of striving to meet aerodynamic reality is that the size of the tunnels has increased, making them logistically difficult to work with in the field and resulting in a tendency to homogenise naturally complex soil surfaces. This homogenisation is at odds with an increasing awareness of the importance that small scale processes have in wind erosion. To address these logistical and surface homogenisation issues we present here the development and testing of a micro wind tunnel (MWT) designed to simulate wind erosion processes at high spatial resolution. The MWT is a duct-type design—0.05 m tall 0.1 m wide and with a 1.0 m working section. The tunnel uses a centrifugal motor to suck air through a flow‐conditioning section, over the working section and then through a sediment collection trap. Simulated wind velocities range from 5 to 18 m s−1, with high reproducibility. Wind speeds are laterally uniform and values of u* at the tunnel bed (calculated by measuring the pressure gradients within the MWT) are comparable with those of larger tunnels in which logarithmic profiles can be developed. Saltation sediment can be added. The tunnel can be deployed by a single person and operated on slopes ranging from 0 to 10°. Evidence is presented here that the MWT provides new and useful understanding of the erodibility of rangelands, claypans and ore stockpiles