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<br />Scholl, D.G., 1971, Soil wettability in Utah juniper stands: Soil Science Society of <br />America Proceedings, v. 35 no. 2, p. 344-345. <br />This study investigated the wettability of soils in a stand of Utah juniper with respect to <br />ground-cover zones, upper prof11e soil horizons, the amount of organic matter, and moisture <br />conditions in the soil. The results indicated that wettability was closely related to organic <br />matter, and that the 0 horizon was far more resistant to wetting than others below it. <br />Results also showed an increased resistance to wetting with decreased moisture content, as <br />expected. The exception to this trend was zone three (the bare soil in an open area beyond <br />the canopy), where the opposite occurred. The paper explained that the latter was probably <br />a wettable soil, according to the classification proposed by DeBano (1966), causing the water <br />drop penetration time to decrease with a decrease in moisture content. Another exception <br />was that water repellency no longer increased above the IS-bar level. The author explained <br />that this was most likely due to the presence of montmorillonite in the soil, which caused <br />cracking and exposure of the more wettable portions. <br /> <br />Scholl, D.G., 1975, Soil wettability and fire in Arizona chaparral: Soil Science Society <br />of America Proceedings, v. 39, no. 2, p. 356-361. <br />The author examined the effects of fIeld and lab fires of variable intensities on the water <br />repellency of soil layers in Arizona chaparral. Although soils were water repellent before and <br />after fire events, the hot fires resulted in water repellency at greater depths and decreased <br />repellency at the surface. Tests also indicated that the water-repellent layers were destroyed <br />at approximately 2700C. The introduction notes other research which indicates that sandy <br />soils tend to cause the most severe water repellency problems due to the small surface area <br />to volume ratio of the grains (thus requiring less material to coat the grains). <br /> <br />Scott, D.F., 1993, The hydrological effects of fire in South African mountain <br />catchments: Journal of Hydrology, v. 150, p. 409-432. <br />The results of this study illustrate the complexity with which variables interact to produce <br />various hydrological responses to fire. Four South African mountain catchments were <br />monitored following fire events to determine the effects on streamflow, storm-flow, and <br />sediment yield. Two of the catchments were covered with scrub vegetation prior to burning, <br />a third with eucalypt forest, and the fourth with pine. Included in the experimental design <br />were tests for water repellency and experimental plots to measure overland flow. In the <br />scrub catchments, researchers observed no increase in storm flow or sediment yield, and <br />increases in annual flow were within model predictions. In contrast, storm flows and <br />sediment yields in the forested catchments increased signifIcantly. Soils in the latter were <br />found to be highly water repellent, although the eucalypt catchment was already naturally <br />water repellent prior to burning. The author attributed the hydrologic response of the <br />forested catchments to large increases in overland flow, resulting from water-repellent soils. <br />The relatively moderate response of the scrub catchments was explained by the fact that the <br />water repellency in these areas was patchy, so although overland flow occurred on steeper <br />slopes, it was able to inf1ltrate into the soil before reaching streams, and thus, did not affect <br />storm flow. The author also suggests that the nature of water repellency in the catchments <br />was the result of vegetation type and bum intensity (which in turn was affected by fuel <br />loading, soil moisture and fuel moisture conditions at the time of burning, and the type of <br />vegetative cover). <br /> <br />35 <br />