|Zobeck, Teddy - Ted|
Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/9/2006
Publication Date: 11/30/2006
Citation: Ravi, S., D'Ordorico, P., Herbert, B., Zobeck, T.M., Over, T.M. 2006. Enhancement of wind erosion by fire-induced water repellency. Water Resources Research. 42:1-9. Interpretive Summary: Wild fires often drastically affect the vegetation on a site, often altering the amount and kind of vegetation present. Fire also changes the surface properties of the soils and often causes increases in the amount of wind erosion as previously covered soils are exposed to the forces of the wind. In addition, certain chemicals are released from plants by burning and these chemical impart a water repellency to the soils that seems to increase the soil susceptibility to wind erosion. In this study we investigated how a representative water repellent organic compound released by burning vegetation and absorbed in the soil may increase soil erosion by wind. We carried out a series of wind tunnel experiments, laboratory tests, and theoretical analyses to test how fire-induced water repellency on the soil affects the soils susceptibility to wind erosion. The experiments were carried out using a clean, well-sorted sand which was artificially coated with palmitic acid, a common water repellent organic compound in soils. The results indicated that fire-induced water repellency increases soil wind erosion. We found that the wind velocity needed to start the soil blowing decreased in soils coated with the organic compound. The results are explained by the effect of water repellent compounds on the forces holding particles together.
Technical Abstract: The occurrence of fire and the subsequent increase in wind erosion are known to affect vegetation dynamics in dryland landscapes. Fires act as a disturbance on shrubs and trees and expose the soil surface to the erosive action of wind, thereby affecting the loss and redistribution of soil nutrients. Despite the relevance of wind erosion and fires to the dynamics of arid ecosystems, the interactions between these two processes remain poorly understood. We have investigated how a representative water repellent organic compound released by burning biomass and absorbed in the soil may enhance soil erodibility. To this end, we carried out a series of wind tunnel experiments, laboratory tests, and theoretical analyses to assess the effect of fire-induced water repellency on the soil susceptibility to wind erosion. The experiments were carried out using a clean, well-sorted sand which was artificially coated with palmitic acid, a common water repellent lipid in soils. The results indicate that fire-induced water repellency enhances soil erodibility, causing a drop in wind erosion threshold velocity. The results are explained by the effect of water repellent compounds on soil-water contact angle and on the strength of interparticle wet-bonding forces.