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

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


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 wind’s ability (impeded by vegetation and terrain) to entrain soil particles, and the soil’s 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, and resultant reduction in the protective cover of vegetation, 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. We have focused on a field site that is partially located on the INL (see figure below). The specific objective for our research at the site is to identify hydroclimatological, vegetation, and microtopographic controls on post-fire wind erosion potential.


Accomplishments through 2009
We continued our monitoring of saltation, aeolian threshold wind velocity, aeolian sediment flux, and soil loss and deposition at the Twin Buttes Fire, Moonshiner Fire, and an adjacent control site. We began this monitoring in September, 2007. The National Center for Airborne Laser Mapping (NCALM) collected a LiDAR remote sensing data set for our study area in November 2007.


We have published a manuscript with Geomorphology describing the relationships of soil loss and deposition and LiDAR-derived land surface roughness for the Twin Buttes and Moonshiner fires and adjacent unburned study areas.


We have published a manuscript in Aeolian Research describing relationships of near-surface, soil and atmospheric climate and post-fire aeolian transport.


We have published our results concerning wind erosion and post-fire fluxes of aeolian sediment on the Snake River Plain (Crystal Fire, 2006 – a study that preceded our research at the INL) in Journal of Arid Environments.


Joel Sankey defended his dissertation entitled “Dynamics of post-wildfire aeolian transport in cold desert shrub steppe” in November, 2009. The majority of the dissertation focuses on work performed at, and adjacent to, the Twin Buttes and Moonshiner fires.


Results
Key findings regarding relationships of hydroclimate and post-fire wind erosion include:

  • The burned soil surfaces became less erodible with time following burning.

  • The decrease in erodibility was explained by variability in soil water content and atmospheric moisture. Specifically, multiple regression models with predictor variables including soil water, atmospheric moisture, and time variables explained 83 percent and 69 percent of the variability in erodibility at the severe (Twin Buttes fire) and moderate (Moonshiner fire) burn intensity sites, respectively.

  • Though erodibility generally decreased with increased moisture near the soil surface, we did observe examples of counter-intuitive relationships where erodibility increased linearly or appeared to vary curvilinearly with increased moisture.

 

Key findings regarding relationships of LiDAR-derived land surface roughness and post-fire wind erosion include:

  • Surface change (aeolian erosion and deposition) varied as a function of surface roughness among burned and unburned surfaces, with net erosion occurring on the relatively smooth, burned surfaces and net deposition occurring on the rough, unburned surfaces.

  • Erosion decreased (and deposition increased) with increased soil and vegetation roughness derived from LiDAR remote sensing analysis.

  • Surface change at fine spatial scales (length scales < 1 m) suggested that aeolian processes occurred with strong spatial patterns on burned, but not unburned surfaces.

 

Plans for Continuation
We are interested in continuing our monitoring work in 2010. Joel Sankey is now serving as a post-doctoral researcher and continuing his investigation into wind erosion of sagebrush-steppe.


Publications, Theses, and Reports

Sankey, J.B., Glenn, N.F., Germino, M.J., Gironella, A.I.N., Thackray, G. D., 2010. Relationships of aeolian erosion and deposition with LiDAR-derived landscape surface roughness following wildfire. Geomorphology doi:10.1016/j.geomorph.2010.03.013.


Sankey, J.B., Germino, M.J., Glenn, N.F., 2009. Relationships of post-fire aeolian transport to soil and atmospheric conditions. Journal of Aeolian Research 1, 75-85.


Sankey, J.B., Germino, M.J., Glenn, N.F., 2009. Aeolian sediment transport following wildfire in sagebrush steppe. Journal of Arid Environments 73, 912-919.


Sankey, J.B., 2009. Dynamics of post-wildfire aeolian transport in cold desert shrub steppe. Ph.D. dissertation, Idaho State University.


Sankey, J.B., Glenn, N.F., Germino, M.J., Hoover, A.N., Gironella, A.I., 2009, Relationships of aeolian surface change with LiDAR-derived landscape surface roughness. American Geophysical Union Fall Meeting, Dec 13-18, San Francisco, CA.