| Aeolian sediment transport is an important contemporary biogeomorphic agent in semiarid shrublands, particularly when wildfire temporarily reduces the protective cover of vegetation. This research examined spatial and temporal differences in aeolian transport for burned and unburned semiarid, cold desert shrub steppe of the eastern Snake River Plain, Idaho. Relationships of soil erodibility to soil and atmospheric conditions, as well as relationships between aeolian surface change and landscape surface roughness were additionally examined in detail following wildfire. Research was conducted at locations burned in late-summer by the Crystal fire (2006) and Twin Buttes and Moonshiner fires (2007) and adjacent unburned locations. Methods included field monitoring of: soil and atmospheric micrometeorological conditions, saltation and associated threshold wind speeds, vegetation cover, changes in relative surface elevation(s), and sediment flux. Remote sensing characterization of landscape surface roughness was performed with a LiDAR dataset. Results indicated that the increase in aeolian transport following burning at all sites was substantial and of a greater magnitude to that reported for many other burned environments of the world, though the increase in transport appeared to persist over a shorter time period in cold desert shrub steppe due to the seasonality of climate and regrowth of herbaceous vegetation in subsequent spring. Soil and atmospheric moisture were determined to be important influences on transport potential during the fall months of high erosion that immediately followed late-summer fire. Erodibility generally decreased with increased moisture during the fall, though more complex relationships were observed - often at finer temporal scales. Surface change varied strongly as a function of landscape surface roughness, with the greatest deflation observed on the relatively smooth, burned surfaces, and greatest inflation observed on the rough, vegetated, unburned surfaces. Furthermore, effects of surface roughness were greater on erosion compared to deposition processes. Spatial analysis suggested that aeolian processes increased the heterogeneity of microtopography in burned surfaces, whereas the downwind surfaces that were unburned experienced a more homogeneous pattern of surface change. Findings of this research have direct application to regional rangeland management, as resource managers determine the best practices for, and implications of, remediation of burned shrub steppe rangelands. |
