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Watson, C.L., and Letey, John, 1970, Indices for characterizing soil-water repellency based upon contact angle-surface tension relationships: Soil Science Society of America Proceedings, v. 34, p. 841-844. This investigation used the relationship between surface tension and apparent liquid-solid contact angle to develop indices for characterizing soil-water repellency. Two indices were proposed. The first involved a water drop test with a series of ethanol solutions to determine the degree of water repellency. The second test evaluated the persistence of water repellency by measuring the time required for a drop of water to be absorbed by the soil. The paper notes that both of these indices are important in classifying water-repellent materials, since a high degree of repellency is not necessarily indicative of persistence. The introduction also provides a summary of other techniques used to characterize and measure the degree of repellency, and discusses some of their drawbacks or advantages. Wells, C.G., Campbell, R.E., DeBano, L.F., Lewis, C.E., Fredriksen, R.L., Franklin, E.C., Froelich, R.C., Dunn, P.H., 1979, Effects offire on soil- a state-of- knowledge review: Washington DC, U.S. Department of Agriculture Forest Service, General Technical Report WO-7, 34 p. This paper summarizes the state-of-the-art for the following fire and soil topics: (1) soil temperature and heating; (2) chemical properties and nutrient cycling; (3) soil microfauna; (4) soil physical properties; (5) erosion; and (6) effects of fire on range soils. A section defIning knowledge gaps, research scope and priorities is included, in addition to an extensive bibliography. A discussion of water repellency is included in the section on soil physical properties. This section describes work presented in DeBano, 1974 and 1966, DeBano et al., 1967 and 1976, Savage, 1974 and Savage et al., 1972 and Scholl, 1975. This work includes a description of a wetting-resistant ash dust layer which results in runoff and erosion. The thickness of water-repellent layers is described as being a function of fire intensity, soil-water content and soil physical properties. Deeper layers result from hotter fires, a dry pre-fIre soil results in a thicker layer, and water repellency is more likely to develop in coarser soils. Water-repellent soils are described as forming due to wildfires in chaparral in Southern Califomia and Arizona, lodgepole pine in Oregon (Dyrness, 1976), and ponderosa pine in Arizona (Campbell et al., 1977). Broadcast burning of logging residue in Montana did not produce appreciable water repellency over medium-to-fine textured soils. However, slash piles burned over coarse-textured soils did produce water repellency. 39