244 Geomorphology (Posters)

Wednesday, 21 October 2009
9:00 AM - 6:00 PM
Hall A

MEASURING POTENTIAL FLUVIAL AND AEOLIAN EROSION FROM A RANGELAND FIRE IN THE MOJAVE-GREAT BASIN TRANSITION ZONE

Paper number: 244-16
Program: Technical Sessions
Time: 9:00 AM – 6:00 PM

Authors

Abstract

Post-fire measurements of water and wind soil erosion as well as vegetation transects are in progress at a lightning-caused fire site (Jacobs) in a Mojave-Great Basin transition shrub community in eastern Nevada. Measurements have been conducted 2, 14, 27, and 52 weeks post-burn both at the burn site and in an adjacent control plot at shrub mounds as well as shrub interspaces. Runoff and sediment transport have been measured with a portable rainfall simulator and potential for aeolian erosion has been measured by a portable wind tunnel (PI-SWERLTM).

Runoff potential increased for at least 3 months post-burn on burned shrub mounds in both channel and ridge top plots, but at 6 months, potential runoff began to decrease. Shrub interspaces within the burn showed runoff potential measurements comparable to unburned control plots. Analysis of runoff demonstrated that within 3 (?) months post-burn, a shift had occurred within the distribution of particles in the runoff from fine sands, silt, and clay to coarser particles. Measurement of aeolian transport potential 2 weeks post-burn clearly indicated that windblown particle suspension was higher in burned locations than in control plots. Within the burn site, emissions were highest from burned shrub mounds and much lower on shrub interspaces. Over a period of one year, the burn site soil has become somewhat more stable with respect to wind erosion. A important consideration in continued wind erodibility is the role of vegetation establishment which increases surface roughness.

The Jacobs site was dominated by blackbrush (Coleogyne ramosissima), an important species in shrub communities on slopes below pinyon pine-juniper forests in the Mojave-Great Basin transition. While long-lived, blackbrush is prone to fires. Within the Ely District of the U.S. Bureau of Land Management in Nevada, over 40 percent of the blackbrush cover has been lost to fires between 2005 and 2009. Thus, soil stabilization of hillslopes where blackbrush communities have burned is of great concern.