Temporal fluctuations of water repellency in forest soils of Galicia, NW Spain. Do soil samples dried at laboratory reflect the potential soil water repellency? (pages 1179–1187)

摘要

Water repellency is a widespread property of Pinus pinaster and Eucalyptus globulus forest soils in NW Spain and is particularlynsevere during the summer dry conditions. The aim of this work was to compare actual water repellency at field-moist samplesnwith potential water repellency after drying at 25 and 105 °C in samples collected at different times of year under four forestnsoils. Also, we investigated whether drying at 25 or 105 °C led to repellency values comparable to the highest levels reachednunder field conditions in the summer with a view to developing an appropriate sampling protocol towards estimating thenmaximum possible water repellency of a given soil as a key to establishing its environmental effects. The actual and potentialnwater repellency was determined by using the water drop penetration time (WDPT) and molarity of an ethanol drop (MED)ntests.nClear seasonal patterns of water repellency were observed from the results for the four forest soils, peaking in the dry periodnand disappearing after prolonged wet periods. Water repellency lasts longer in sandy loam soils than in more finely texturednsoils, and also under eucalyptus than under pine forests. Drying soil samples at 25 or 105 °C increased water repellency, asnmeasured with the WDPT method, in the four soils, but especially in the non-repellent samples collected during the wet period.nThe increase was more marked in the sandy loam soils than in the more finely textured soils, and also after drying at 105 °Cnthan at 25 °C. MED measurements exposed a common trait in the four soils; thus, the water repellency values obtained undernfield conditions in summer invariably exceeded those obtained after drying at 25 or 105 °C. In addition, the repellency valuesnfor dried samples collected in the wet period were never comparable to the maximum levels observed under field conditionsnin the summer. Copyright  2011 John Wiley & Sons, Ltd.