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.
