Aeolian processes: an overlooked driver of state change in drylands

Changes in land cover have been observed occurring globally in arid and semi-arid environments, and particularly the transition from grass to shrub dominated environments. Previous research has hypothesized that precipitation and nutrients are the primary drivers responsible for this transition from grass to shrubs. However aeolian processes have also been identified as having a critical role influencing the distribution, and shifts in arid vegetative patterns. Therefore, it is important to understand how aeolian processes will influence changes in land cover, and in particular the transition from grass to shrub dominated environments. The focus of this study in particular is to evaluate how aeolian processes act as the primary mechanism promoting shrub encroachment. In order to better understand these processes as well as their role in changing vegetation patterns, we have developed a portable aeolian laboratory (PAL). This PAL is capable of being deployed either in the field or in a laboratory to measure and quantify the effects of these aeolian processes on vegetation. The PAL consists of a portable wind tunnel that is able to simulate aeolian transportation of sediment that has been observed in the field. It is also capable of measuring wind speed, saltation, temperature, relative humidity, sediment size distribution, as well as the sediment flux profile. We address the following questions in this study (1) how various grass and shrub species in the Chihuahuan desert respond to aeolian transportation, and (2) how inter species responses vary as well.