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<br />Giovannini, G., and Lucchesi, S., 1984, Differential thermal ana: ysis and infrared <br />investigations on soil hydrophobic substances: Soil Science, v. 137, no. 6, p. <br />457-462. <br />The differential thermal analysis (DTA; of a water-repellent soil colected in a coastal pine <br />forest was characterized by two exothermic peaks in the temperature: range of 220 to 5500C. <br />Extraction of the soil with benzene resulted in suppression of the see ond exothennic peak as <br />well as the nonwettable property. The OTA coupled with IR speccophotometry suggested <br />that the soil's water-repellency may be due to a fraction or organic mlterial witha low degree <br />of humifIcation. The IR investigation and fractionation by absorpion chromatography of <br />the exttacted substances show a grea complexity; the only hYl'othesizable compound <br />arrangement was an ester betw,:e::l phenolic acids and polysacdaride substances. The <br />complete combustion curve of the soil's water repellent substances suggested that only <br />temperatures above 5500C can desnoy the nonwettable property in the soil. <br /> <br />Giovannini, G., Lucchesi, S., and Cervelli, S., 1983, Water repellent substances and <br />aggregate stability in hydrophobic soil: Soil Science, v.l35, no. 2, p. 110-113. <br />This study examined the correlation between soil water repellency and aggregate stability. <br />Researchers suggested that less polar compounds were more hydrophobic. These <br />substances were extracted from a water-repellent soil using benzene, and then applied to soil <br />aggregates from a wettable soil. The authors concluded that hydrophobic substances <br />increased aggregate stability by behaving as cementing substances. In a wettable soil, <br />increased aggregation usually improves infiltration and thus reduces erosion. However, this <br />paper suggested that in a hydrophobic soil, water-repellent aggregHes would lead to more <br />erosion than in a wettable soil. <br /> <br />Giovannini, G., Lucchesi, S., and Giachetti, M., 1987, The natUJ'al evolution of a <br />burned soil: a three-year investigation: Soil Science, v. 143, no. 3, p. 220-226. <br />Fire-induced physicochemi.cal ch,nges in a soil were evaluated three years after an <br />experimental bum in Italy. In order to determine the effect of tirle, the same parameters <br />were evaluated in this investigation as in a previous study of the sane area (Giovannini and <br />Lucchesi, 1983). Results showec that the A horizon had experiencd a decrease in organic <br />matter, destruction of water repellency, and a decrease in the water stability index values of <br />soil aggregates immediately following the fIre. All of these param :ters increased after the <br />burn, and reached pre-fIre levels by the third year. Although the B1 ar,d B horizons <br />exhibited an increase in organic matter following the fire, these leve.s did not change during <br />the three years of subsequent monitoring. <br /> <br />18 <br />