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In DDT-treated forest floor columns, over 30 times as much DDT was recovered by leaching with water when urea was added to disperse the humic acids. Using similar treatment and analysis, alundum tension lysimeters in soil 2 cm below the forest floor yielded no detectable levels of DDT. In DDTtreated humic extracts, 91% of added o,p'-DDT was recovered in humic acids and 9% in fulvic acids plus water.Additional Key Words for Indexing: DDT, forest humus, humic acid, lysimetry.

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Subalpine soil temperature regimes were compared for bare ground (BG), evergreen shrub (ES), herbaceous meadow (HM), single tree (ST), and tree clump (TC) sites. Through most of the snow-free season, soil temperatures at-60 cm were BG > ES HM > ST > TC. Relative diurnal temperature amplitudes (percent of BG value) at-5 cm averaged ES, 43; TC, 14; HM, 84 (early summer), 52 (midsummer), 36 (late summer), 45 (fall). Surface temperatures potentially lethal for tree seedlings (-49?C) occurred on HM in early summer. Nonperiodic soil cooling was associated with rainy periods. Fourier analysis and heat conduction models were used to evaluate damping depths, thermal diffusivities, profile homogeneity, and temperature regimes. The equation describing sinusoidal temperature fluctuations in a homogeneous soil proved to be a useful basic model. In this case, D is equivalent to (2K/o))2, where K is thermal diffusivity. The angles in Equation (1) are expressed in radians.