Genesis and Classification of Termite-Mediated Soils along Toposequences in a Semiarid Area of Southeast Ethiopia

Abstract

Despite the ecosystem functioning they provide, termite pedoturbation along toposequence is overlooked in the genesis of semiarid soils. Therefore, we aimed to describe morphological and physicochemical properties that lead to the classification of termite-mediated soils. In this study, representative pedons, one on each slope class, were described and classified for five different topographical positions, and the soil properties of genetic horizons were compared to those obtained from respective mounds. The result showed that the soils were heavily manipulated by termites except for the pedon at the toe slope. Cambisols were formed on the summit and back slope and resulted from slow pedogenic processes. Luvisols on the toe slope showed redoximorphic features, and gleization and clay synthesis formed the soil, while the upward movement of coarse particles enhanced textural differentiation. Luvisols at the foot of the slope are formed by the partial destruction of iron-bearing minerals accompanied by eluviation-illuviation processes. Accumulation of calcium carbonate following calcification formed Calcisols on the bottom slope. Comparing the mounds and reference pedons, much of the mound’s soil is mined from the subsoil, usually from B horizons. However, their influence on soil properties depended mainly on the topography. Moreover, the morphological and physicochemical properties of the studied pedons exhibited various degrees of variation along topography and clearly showed topographic effects. In conclusion, termites can be a potent mediator of soil genesis across toposequences, and their activities should be considered in the classification and management of semiarid soils. A further retrospective examination of micromorphological evidence is recommended to support this finding.

Numerical classification of termite-mediated soils along toposequences and rangeland use influenced soil properties in southeast Ethiopia

“…The representative AB horizons in the first cluster may reflect termite-induced limited OC content mixed in the surface soil. In addition to the Isopteric supplementary qualifier [ 20 ], termite footprints could be reflected by granular, crumbly, or weak fine to medium sub-angular blocky structures and gradual to diffuse horizon boundaries [ 1 ] for all profiles, except for the soil at the toe slope. The second-best representative Bg horizon of Profile 3 in the first cluster probably indicated gleization due to cyclic oxidation and reduction processes, which favored the hydrolysis of primary minerals and enhanced clay formation.…”

“…Termites are an important agent of pedogenesis, affecting soil ecosystem functioning in arid and semi-arid regions [ [1] , [2] , [3] , [4] ]. As key bioturbators, termites affect soils by loosening, selecting, translocating, and mixing various soil particles to maintain the functional properties of their mounds [ 5 ].…”

“…However, quantitative soil classification has not been explored previously for termite-mediated soils, and the extent to which it differentiates the established soil classes is not known. Since termite-inhabited areas in southeast Ethiopia are characterized by gently undulating landscapes [ 1 ], several studies have highlighted the influence of topographic positions at sub-watershed and watershed levels in the country [ 17 , 18 , 48 ]. On the other hand, while addressing soil spatial variability at the continent scale, a global soil classification system excludes topsoil variability and may only contribute a small amount to soil variability at the micrometer scale [ 49 ].…”