Soils on Terraces Along the Cauca River, Colombia: I. Chronosequence Characteristics

Abstract

AbstractSoils on two floodplain and six terrace levels, developing under lowland tropical evergreen or semideciduous forest before recent deforestation, were studied to determine the properties found to vary most with relative age. They are in a sequence from a Typic Tropaquent and an Aeric Tropaquept on the two floodplain levels through Haplustults and Paleustults to a Tropeptic Haplustox on the highest terrace. The soil properties may be placed into three categories based on their variations with relative soil age. (i) Soil properties which are similar in all of the terrace soils are bulk density, clay content in the B horizons, 15 bar water retention, organic C content, and dithionite‐citrate‐extractable Fe. Differences in soil morphology are small, other than the relative thinness of the solum in the soil on the lowest terrace, an anomalous (with respect to age) hardpan in the soil on the next terrace, and slightly higher chroma in the soils on the two highest terraces. (ii) The proportions of different exchangeable cations exhibit age trends in the younger (lower) terrace soils but are either similar in the older (higher) terrace soils or so erratic that an age trend is not apparent. (iii) Except for properties of the clay fractions, only the extractable Fe ratio (Feo/Fed) was found to vary systematically through the entire sequence of terrace soils. It decreases from slightly > 0.4 in the lower floodplain soil to < 0.01 in the lower solum of the oldest soil.