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ARS Home » Plains Area » Lubbock, Texas » Cropping Systems Research Laboratory » Wind Erosion and Water Conservation Research » Research » Publications at this Location » Publication #202146
Title: The effect of fire-induced soil hydrophobicity on wind erosion in a semiarid grassland: Experimental observations and theoretical framework

Author
item RAVI, SUJITH - UNIV OF VIRGINIA
item D'ORDORICO, PAOLO - UNIV OF VIRGINIA
item Zobeck, Teddy
item OVER, THOMAS - EASTERN ILLINOIS UNIV

Submitted to: Geomorphology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2007
Publication Date: 4/1/2009
Citation: Ravi, S., D'Ordorico, P., Zobeck, T.M., Over, T.M. 2009. The effect of fire-induced soil hydrophobicity on wind erosion in a semiarid grassland: Experimental observations and theoretical framework. Geomorphology. 105(1-2):80-86.

Interpretive Summary: Arid areas are often subjected to disturbances such as fire and grazing. When disturbances expose the soil surface wind erosion may act to move soil particles and soil nutrients important in plant growth. This movement in plant nutrients may be related to conversion of land from grassland to shrubland. Wind erosion continues the redistribution of plant nutrients by selectively removing soil from between the shrubs in the bare areas and depositing it at the base of the shrubs. Although fire and wind erosion interact to affect the patterns of vegetation in semiarid lands, few studies have investigated the interactions. Using soil samples collected after a wildfire event at the Cimarron National Grasslands in southwestern Kansas, we demonstrate through a series of wind tunnel experiments, laboratory measurements, and theoretical analyses how wind erosion can be enhanced by fire-induced water repellency. Results from the wind tunnel experiments show that in semiarid grasslands fires can cause a decrease in wind speed needed to move particles during wind erosion thereby increasing the post-burn erosion of (hydrophobic) soils. Further, we developed a mathematical model explain the decrease in the wind speed needed to start wind erosion in water-repellent soils.

Technical Abstract: Aridland ecosystems are often susceptible to degradation resulting from disturbances like fires and grazing. By exposing the soil surface to the erosive action of winds, these disturbances contribute to the redistribution of soil nutrients associated with grassland-to-shrubland conversions, and to the formation of a heterogeneous landscape. Wind erosion maintains the local heterogenties in nutrient and vegetation distribution in arid landscapes through the removal of nutrient-rich soil from the intercanopy areas and the subsequent deposition of soil onto vegetation patches. Even though wind erosion and disturbances like fires strongly interact with each other and determine vegetation patterns in arid landscapes, very few studies have addressed these interactions. Using soil samples collected after a wildfire event at the Cimarron National Grasslands in southwestern Kansas, we demonstrate through a series of wind tunnel experiments, laboratory measurements, and theoretical analyses how wind erosion can be enhanced by fire-induced water repellency. Results from the wind tunnel experiments show that in semiarid grasslands fires can cause a decrease in wind erosion threshold velocity thereby enhancing the post-burn erosion of (hydrophobic) soils. Further, a generalized process-based theoretical equation was derived to explain the decrease in threshold friction velocity in water-repellent soil for the case of soil particles modeled as asymmetrical cones.