Soil–landscape relationships in the basalt-dominated highlands of Tigray, Ethiopia J. Van de Wauw a, ⁎, G. Baert b , J. Moeyersons c , J. Nyssen d , K. De Geyndt e , Nurhussein Taha f , Amanuel Zenebe f,g , J. Poesen g , J. Deckers e a Laboratory of Soil Science, UGent, Krijgslaan 281/S8, B-9000 Gent, Belgium b BIOT Department, Hogeschool Gent, Voskenslaan 270, B-9000 Gent, Belgium c Royal Museum for Central Africa, Leuvensesteenweg 13, 3080 Tervuren, Belgium d Geography Department, UGent, Krijgslaan 281/S8, B-9000 Gent, Belgium e Laboratory for Soil and Water, K.U.Leuven, Celestijnenlaan 200E, B-3001 Heverlee, Belgium f Department of Land Resource Management and Environmental Protection Mekelle University, P.O. Box 231, Mekelle, Ethiopia g Physical and Regional Geography, K.U.Leuven, Celestijnenlaan 200E, B-3001 Heverlee, Belgium ABSTRACT ARTICLE INFO Keywords: Soilscape Ethiopia Soil map Landscape Catena Pedogeography Though knowledge about the distribution and properties of soils is a key issue to support sustainable land management, existing knowledge of the soils in Tigray (Northern Ethiopian Highlands) is limited to either maps with a small scale or with a small scope. The goal of this study is to establish a model that explains the spatial soil variability found in the May-Leiba catchment, and to open the scope for extrapolating this information to the surrounding basalt-dominated uplands. A semi-detailed (scale: 1/40 000) soil survey was conducted in the catchment. Profile pits were described and subjected to physico-chemical analysis, and augerings were conducted. This information was combined with information from aerial photographs and geological and geomorphologic observations. The main driving factors that define the variability in soil types found were: 1) geology, through soil parent material and the occurrence of harder layers, often acting as aquitards or aquicludes; 2) different types of mass movements that occupy large areas of the catchment; and 3) severe human-induced soil erosion and deposition. These factors lead to “red-black” Skeletic Cambisol– Pellic Vertisol catenas on basalt and Calcaric Regosol–Colluvic Calcaric Cambisols–Calcaric Vertisol catenas on limestone. The driving factors can be derived from aerial photographs. This creates the possibility to extrapolate information and predict the soil distribution in nearby regions with a comparable geology. A model was elaborated, which enables the user to predict soil types, using topography, geomorphology, geology and soil colours, all of which can be derived from aerial photographs. This derived model was later applied to other catchments and validated in the field. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Land degradation, including soil erosion and soil mining are serious problems in the Ethiopian Highlands. To reverse these trends, many soil conservation programs have started in these regions. Adequate knowledge about the distribution and properties of soils is a key issue to support sustainable land management, which, among others, includes erosion control, fertility management, crop choice, risk of mass movements and possibilities for irrigation. However, existing knowledge of the soils in Ethiopia's northernmost Tigray region is limited to either maps with a small scale (Virgo and Munro, 1978; Nedeco, 1997; BoANR-LUPDR, 2000) or with a small scope (Assefa, 2005; Nyssen et al., 2008). Because intensive soil-surveys are very expensive, one smaller catchment, the May-Leiba catchment (1800 ha) was chosen as a reference for the surrounding basalt-dominated uplands of the Geba catchment. The goal of this study is to establish a model and a soil map that explains the spatial soil variability found in the May-Leiba catchment, and to open the scope for extrapolating this information to the surrounding basalt-dominated uplands. To create the soil map, different approaches are possible: the pedologic approach and the physiographic or geomorphologic approach (Wielemaker et al., 2001). The first method tries to create maps with taxonomic pure soil data or soil associations. The geomorphologic approach uses soils as part of the landscape. We have chosen for this geomorphologic approach because extrapolating the results of the soil map needs this geomorphologic information, and we believe that for most uses of the soil map will be combined with this geomorphologic information. Within this geomorphologic approach, digital soil mapping methods are used increasingly (e.g. Moore et al., 1993). For this study however, we have chosen the more classic approach by using aerial photographs, due to the high Catena 75 (2008) 117–127 ⁎ Corresponding author. E-mail address: johan.vandewauw@ugent.be (J. Van de Wauw). 0341-8162/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.catena.2008.04.006 Contents lists available at ScienceDirect Catena journal homepage: www.elsevier.com/locate/catena