POST-FIRE WIND EROSION IN SEMIARID SHRUB STEPPE: OBSERVATIONS FROM FIELD AND REMOTELY SENSED DATA

The objective of this project is to determine and describe the effects of fire on the potential for soil erosion by wind in a semiarid shrub steppe in southeastern Idaho. We apply a previously developed method for determining the threshold wind speed (critical threshold) required to initiate saltation of soil particles at 3 sampling locations within a wildfire that burned in August, 2006. Each location has a data collection station with two anemometers mounted above and below the vegetation canopy, a piezoelectric sensor mounted at 5 cm above the ground surface that records impacts from saltating soil particles, and temperature and relative humidity sensors mounted at ground level. We present results from four months of data collection immediately following the fire. Analysis is intended to identify key controlling variables of post-wildfire eolian transport with the intention of continued monitoring over longer time periods. Initial field results indicate substantial differences in wind erosion potential between burned and unburned sites. Saltation activity is greater and more frequently detected at two burned sites in comparison to an unburned site. Comparison between the burned sites indicates periods of similar saltation activity and threshold wind speeds. Comparison also shows periods when saltation is detected at one burned site but not the other, and periods when greater wind speeds are required at one burned site to initiate saltation. This suggests that within-burn variability exists in wind erosion potential and requires more complete characterization to accurately model and predict post-fire eolian transport. In parallel to the field-based research, we are developing remote sensing techniques to characterize the soil and vegetation communities at a scale appropriate for wind erosion modeling. These techniques include hyperspectral and LiDAR analysis of the soil surface and structural information of the vegetation. Soil and vegetation surface roughness information from LiDAR will be used to compare wind speed thresholds in the field areas. This work has important implications for land rehabilitation, soil conservation efforts, and human health (air quality).