[1] Univ Leon, Dept Appl Phys, E-24071 Leon, Spain
[2] UV GV, CSIC, Desertificat Res Ctr CIDE, Dept Environm Qual & Soil, Valencia 46113, Spain
[3] Univ Malaga, Dept Geog, Inst Geomorfol & Suelos, E-29071 Malaga, Spain
[4] Wageningen Environm Res, Team Soil Water & Land Use, POB 47, NL-6700 AA Wageningen, Netherlands
[5] Univ Newcastle, Civil Surveying & Environm Engn, Callaghan, NSW 2308, Australia