USE OF NUMERICAL ESTIMATORS AND MULTIVARIATE-ANALYSIS TO CHARACTERIZETHE GENESIS AND PEDOGENIC EVOLUTION OF XERALFS FROM SOUTHERN SPAIN

Eight xeralfs from the province of Jaen in the region of Andalusia (so uthern Spain) were studied. The micromorphology and mineralogy of the clay and sand fractions from the Bt horizon, among other characteristi cs, were investigated, and indices of pedogenic evolution, including r elative redness index, relative development index of color and the rel ative development index of color + structure, clay illuviation index, anisotropy index for clay content, iron release index and kaolinite/sm ectite ratio, were calculated. These findings were supported by the re sults of factorial analysis (R mode) and correlation between variables . We found micromorphological evidence of clay illuviation (even in ca lcareous soils), alterations leading to clay formation, argillopedotur bation, coating disruption by carbonates, and polycyclicity. The clay fraction was essentially illitic, with smaller amounts of kaolinite, s mectite and interstratified phases. Alterations were therefore moderat e. Numerical estimators of evolution were informative of some specific pedogenic processes, and confirmed the influence of certain soil form ation factors and the relative degree of evolution of different soils. The soil system comprising the xeralfs can be defined in terms of fou r factors that grouped the soil variables, and accounted for more than 90% of the variance: Factor 1, pedological development of the Bt hori zon; Factor 2, a mineralogical factor; Factor 3, clay translocation in the profile; and Factor 4, a mineralogenetic feature of the Bt horizo n.