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 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 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 (Pearson’s 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 – Inland
Northwest Research Alliance
NCALM –
National Center for Airborne Laser Mapping
