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Bashir, S.M., 1969, Hydrophobic soils on the east side ofthe Sierra Nevada: Reno, University of Nevada, M.S. th'~sis, 97 p. The occurrence of water repellency on the east side of the Sierra );Ie' 'ada was evaluated with respect to a variety of soil and cover types. Three general soil textur,:s were evaluated in the study, including sandy, loamy, and floe loamy soils. In addition to b ue soils, the four cover types included Jeffrey pine, manzanita, snow brush, and bitter bru~h. The results showed that water-repellent conditions occurred in all major soil types und er litter, and that there was no good correlation bel:ween the nature of repellency and litte! depth. Texture, burn- intensity, and the presence of furgi i:lfluenced the degree of W:Lter repellency, but no differences were found bet,,/een the four cover types. Sandy soils also had deeper water- repellent layers than fine loams or loams. This study found that in a 11 cases (even in burned areas), water repellency began at the mineral surface. This is in contl ast to other studies that have described the occurrence of post..fIre water-repellent layers 1 or 2 inches below the surface (beneath a wettable layer). Fire in this case did, howeve:', induce repellency, or intensify existing repellency. The author notes that the results of the capillary rise technique used by Emerson and Bond (1 %3) 'CO measure the degree of water repellency, were umeliable when used on soils containing high percentages of silt, c .ay, and organic matter. The literature review contaIns historic information on various cau ;es of water repellency, including findings from some European literature that relate iron :0 wetting resistance in soils. Bisdom, E.B.A., Dekker, L.W., am.d Schoute,J.F.Th., 1993, Wat~r repellency of sieve fractions from sandy soils and relationships with organil material an soil structure: Geoderma, v, 56, p. 105-118. Researchers investigated the relalionship between water repellency and soil constituents of agricultural and uncultivated sandy wils in the southwestern Nether! mds. The study offered insight into the variables affectirg water repellency in sandy soils wd comp:ued results to the proposed causes of repellency t:mnd in other literature. While ( ther investigations have attributed water repellency prim~ily to "coatings" on soil part Lcles, this study found interstitial material to be the dominant factor. These findings were supported with electron microscopy photographs of sand grain surfaces which showed velY little organic material remaining after soil samples were washed with water (thus removin,s the interstitial material and rendering samples wettable). Researchers also determined that fresh and partly decomposed organic matter had h:gher water-drop penettation tin les than more degraded fragments. The authors conclude':. that further studies are needed to establish the role of biota in water repellency. 4