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<br />Crockford, H., Topalidis, S., and Richardson, D.P., 1991, Water repellency in a dry
<br />sclerophyll eucalypt forest- measurements and processes: Hydrological
<br />Processes, v. 5, p. 405-420.
<br />This study examined the water repellency at numerous sites in an Australian eucalypt forest
<br />over a period of four years. Field measurements were supplemented with lab experiments
<br />that attempted to identify some of the processes taking place. Results indicated that several
<br />weeks of cool, wet weather were required for water repellency to break down, and a much
<br />shorter period of hot, dry weather for it to be reestablished. Three possible explanations
<br />were proposed as to the mechanism of breakdown during prolonged wetting: 1) clay
<br />aggregates may disaggregate and expose wettable surfaces; 2) litter may swell and enlarge
<br />water entry paths; or 3) hydrophobic compounds may undergo chemical transformations.
<br />The authors also note that water repellency in pine forests was due to fungal hyphae (a
<br />surface phenomenon), and was consequendy reduced during mixing for lab preparations,
<br />whereas the repellency of eucalypt forest samples resulted from organic matter and was not
<br />so easily disrupted.
<br />
<br />DeBano, L.F., 1969a., Observations on water-repellent soils in western United States,
<br />in DeBano, L.F., and Letey, John, eds., Water-repellent soils: University of
<br />California, Riverside, May 6-10, 1968, Proceedings, p. 17-29.
<br />This paper describes the theory behind water repellency and discusses the implications with
<br />respect to soil-moisture relationships. Figures of moisture retention and evaporation curves
<br />for water-repellent and wettable soils are included The paper also discusses inf1ltration and
<br />diffusivity, with accompanying tables and wetting curves. Experimental results suggest that
<br />water repellency will alter unsaturated flow (both during evaporation and inf1ltration), and
<br />thus needs to be taken into account when modeling water movement. The author proposes
<br />that the capillary changes resulting from differences in apparent liquid-solid contact angles
<br />explain some of the effects of hydrophobic substances. He also suggests that moisture
<br />transfer in water-repellent soils may be dominated by vapor flow, whereas liquid flow is
<br />probably more important in wettable soils.
<br />
<br />DeBano, L.F., 1969b., Water movement in water-repellent soils, in DeBano, L.F., and
<br />Letey, John, eds., Water-repellent soils: University of California, Riverside,
<br />May 6-10, 1968, Proceedings, p. 61-89.
<br />This paper provides an introduction to some basic concepts involving water repellency and
<br />the effects on water movement. It includes information on relationships between soil
<br />moisture and tension, and soil-moisture distribution, in repellent and wettable soils. Also
<br />included are inf1ltration curves for conditions in layered and unlayered soils.
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