A Livestock Trampling Function for Potential Emission Rate of Wind-blown Dust in a Mongolian Temperate Grassland

Abstract. Mongolian Grasslands is one of the natural dust source regions and it contributes to anthropogenic dust due to its long tradition of raising livestock. Decades of abrupt changes in a nomadic society necessitate a study on effects of livestock trampling on dust emissions, so that research studies may help maintain sustainable ecosystem and well-conditioned atmospheric environment. For scaling the effect strength of trampling, therefore, we conducted a mini-wind tunnel experiment (by PI-SWERL® device) to measure dust emission fluxes from trampling (at 3 disturbance levels of livestock density, N) and zero trampling (the background level) at test areas in a Mongolian temperate grassland. We found the substantial increase in dust emissions due to the livestock trampling. This positive effect of trampling on dust emissions was persistent throughout all wind friction velocities, u* (varying from 0.44 to 0.82 ms−1). Significantly higher dust loading had occurred after a certain disturbance level has reached by the livestock trampling. Our result suggests that both friction velocity (u*) and disturbance level of livestock density (N) has enormous combinational effect on dust emission from trampling test surface. Furthermore, we successfully developed a livestock trampling function dependant on u* and N. In the livestock trampling function, almost 4 times greater of determinant power for u* than of for N was determined (fL (N, u*) ∼ N1.1u*4). It points that the effect strength of trampling get magnified with an increase in u*, and, therefore dust will emit much as stronger wind prevails at the trampled surfaces. This finding indicates that the effect of trampling can be seen or get into a play in emission when wind is strong. It emphasizes that a better management for livestock allocation coupled with strategies to prevent dust loads is needed, however, there are many uncertainties and assumptions to be improved in this study. The applicability of our result is feasible with a care to other areas beyond the study location.