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<br />Meeuwig, R.O., 1971, Inliltration and water repellency in granit.c soils: <br />Intermountain Forest and Range Experiment Station, Ogden, Utah, U.S.D.A. <br />Forest Service Res,earch Pape:t INT-l11, 20 p. <br />Natural water repellency in the Cuson Range of the Sierra Nev:lda was evaluated with <br />respect to its impact on runoff and inf1ltration patterns in granitic soils. The study correlated <br />measurements of water repellency \mder different plant covers with data from infIltrometer <br />tests and rainfall simulators to determine the net effects of the resF ,ective vegetation types. <br />The soils involved were sands and sanely loams with clay contents :anging from 2.4-4.5 %. <br />Eight general types of wetting pal:tems were noted, based on visual (,bservations trom hand- <br />dug trenches. These wettlng pattems (illustrated with cartoons) tendod to be associated with <br />characteristic runoff values. R,~sults indicated that water repell<:ncy was most intense <br />beneath pine litter at higher elevations. However, the author sugge ;ted that, in most cases, <br />the presence of an understory ('",i:h its associated root channels) and soil fauna activity, <br />broke up the continuity of the water-repellent layer, and thus, mitigated the impermeability <br />of the soil. In contrast, water reF eD ency beneath chaparral vegetatic n was found in patches, <br />rather than a continuous lay,~r, and (lid 1'.ot appear to impede inf1ltrat on. <br /> <br />Megahan, W.F., and Molitor, D.C., 1975, Erosional effects ofwildfire and logging in <br />Idaho, in Watershed Mllnagement Symposium: Americ: III Society of Civil <br />Engilneers, Irrigation and Drainage Division, Logan, Utili, August 11-13, 1975, <br />p. 423-444. <br />A very hot wildfire over both C:.earcut and uncut watersheds pro, 'ided the setting for an <br />evaluation of erosion following wild fire~. Sandy loam to loamy sand soils overlie moderately <br />fractured bedrock of the Idaho ~atholith. Vegetation (before the fIre) was typical of the <br />seral stage of the Douglas-fir/nine~ark habitat type with an overslory of ponderosa pine, <br />and lesser amounts of Douglas-fIr ar.d Engelman spruce with ;l!l understory of small <br />Douglas fIr, ninebark and huckleberry. The authors found that t!.e percent frequency of <br />occurrence of water repellency was about equal on both the harveste:l and uncut watersheds. <br />However, both the average thic:mess :and the maximum thicknes:: of the water-repellent <br />layer was greater on the clearcllt watershed. The average and maximum thickness of <br />repellent layers tended to decrease with time on both watershe ds. Paradoxically, the <br />frequency of sites exhibiting watt:r-repellent soils increased on bot! study watersheds after <br />one year. Based on erosion pin data, there was a tendency for g :eater erosion from the <br />clearcut area, specifIcally from areas with thicker water-repellent laye:'s. <br /> <br />28 <br />