Characterization and genesis of soils derived from sedimentary rocks in the Crocker Formation, Sabah, Malaysia

Soil properties in three rain forest types and six different elevations (921, 1173, 1317, 1556, 1727 and 1932 m above sea level) were studied at Mount Alab, Sabah. The chosen study site consisted of soils derived from sedimentary rocks of the Crocker Formation aged from Late Eocene to Early Miocene. Results of this study showed that soils with difference in elevation demonstrated considerable variations in term of morphological and physicochemical properties depending on the nature of the parent materials. At the highest elevation, the soil profile presented with a thin surface organic layer. On the other hand, the soils changed from Inceptisols to Ultisols with decreasing elevation. All soils were moderately acidic with an abundance of sand in these soil profiles due to the dominance of sandstones in their parent materials. Clay fraction of these soil profiles was dominated by clay-sized quartz while illite, kaolinite, interstratified illite-vermiculite, gibbsite and vermiculite were present in low or minor amounts. The chemical properties of the soils were significantly affected by topographical positions. The highest value of total organic carbon and total nitrogen were obtained at the summit, whereas, toeslope had relatively more exchangeable calcium and aluminium. Therefore, soil quality was better at higher topographical positions in this study.