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Dynamics of Post-wildfire Wind Erosion of Soil in Semiarid Rangelands, Idaho 

Background

Aeolian sediment transport is a fundamental geomorphic process that has wide-ranging environmental implications for human and environmental health, ecological functioning at multiple spatial and temporal scales, local and global biogeochemical cycling, and contaminant transport. Aeolian sediment transport is a function of the windís ability (impeded by vegetation and terrain) to entrain soil particles, and the soilís susceptibility to this entrainment. Field-based research on aeolian transport in non-agricultural systems has largely focused on arid landscapes, however semiarid landscapes, and shrublands in particular, exhibit considerable annual fluxes of wind-transported sediment. The addition of fire in semiarid landscapes can generate locations that are susceptible to substantial, locally recurring wind erosion.

Objectives

The overall goal of our research is to determine and describe wildland fire effects on wind erosion potential of shrub steppe in southeastern Idaho. The specific objective for our research at the INL Site is to identify hydroclimatological and vegetation controls on post-fire wind erosion potential.

Accomplishments Through 2007

We have monitored saltation, aeolian threshold wind velocity, aeolian sediment flux, and soil loss and deposition at the East Butte Fire, Moonshiner Fire, and an adjacent control site since September 2007.

We have submitted an abstract with our results on hydroclimatological controls on post-fi re wind erosion to the International Grasslands Congress (IGC) in Huhot, China (July 2008). We are preparing a manuscript based on the hydroclimatological results submitted to IGC. NCALM collected a lidar data set for our INL Site study area in November 2007. We will use this data to investigate vegetation controls on post-fire wind erosion potential.

Results

Little saltation activity was detected and threshold could not be assessed at the unburned site. Threshold increased during the course of the study at the burned site (Figure 9-10a), suggesting that erodibility was highest immediately following fire and decreased throughout fall. Water, temperature, and relative humidity (Figure 9-10b, c, and d) were moderately-strongly correlated with threshold (Pearsonís correlation = 0.70, -0.68, 0.76, respectively, all p < 0.00). A multiple regression model with relative humidity and water as predictors explained substantial variability in threshold (threshold = 6.92 * 0.02 relative humidity * 0.10 water, r2 = 0.75, p-values < 0.00).

Preliminary findings from this study suggest that wildland fire has the potential to increase wind erosion susceptibility in the semiarid rangeland environment we studied. Erodibility, as measured by daily mean threshold wind speed, appeared to be highest in the weeks immediately following fire. Both subsurface hydrology and boundary layer atmospheric conditions appear to be major controls on the dynamics of post-fire wind erosion.

Plans for Continuation

We intend to continue our monitoring work through at least fall/winter 2008.

Publication, Reports, Theses, etc.

We have submitted an abstract with our results on hydroclimatological controls on post-fi re wind erosion to the IGC in Huhot, China (July 2008). We are preparing a manuscript based on the hydroclimatological results submitted to IGC.


Investigators and Affiliations

Joel B. Sankey, Graduate Student, Engineering and Applied Science, ISU, Pocatello, Idaho

Nancy F. Glenn, Professor, Geosciences Department, ISU, Pocatello, Idaho

Matthew J. Germino, Professor, Biological Sciences Department, ISU, Pocatello, Idaho

Funding Sources

INRA Ė Inland Northwest Research Alliance

NCALM Ė National Center for Airborne Laser Mapping

U.S. Department of Defense
 


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