Characteristics and classification of soils of Gora Daget forest, South Welo highlands, Ethiopia

Abstract

The soils of the slopes of the South Welo highlands have been either intensively cultivated or overgrazed and eroded. As a result there are few sites where undisturbed soils exist for use as a reference against which the impacts of land use can be evaluated. The Gora Daget forest on a very steep slope located close to Dessie town provides one of these rare opportunities for the type of investigation. Three pairs of representative soil profiles that formed under this indigenous mixed juniperous forest were investigated to establish the soil characteristics and identify the grouping within the fao/unesco classification system. The depths of the soils ranged from less than 30 cm to slightly more than a meter. The solum in all soil types showed very little horizon differentiation and comprised of only Ah horizon, where it is shallower, and Ah and ac horizons where it is deeper. The Ah colour is invariably dark brown (10yr2/2) while the ac is black (10yr2/1). The crumb structure and the loam texture typifying the surface soils changes very little with depth. The main minerals constituting the clay fraction were mica, morderite and sepiolite while those comprising the skeletal fraction were pyroxenes, anorthoclase, plagioclase, morderite, quartz, and magnetite. The organic carbon and total nitrogen are generally high but available phosphorus is low. The pH is within a range suitable to most plants while both the cec and base saturation values registered for the soils were high. The A-horizons were mollic and the soil units were identified as Mollic Leptosols and Mollic Phaeozems. All of the soils showed transitional characteristics with Andosols necessitating their third-level categorization as Andi-mollic Leptosols and Andi-mollic Phaeozems.

SINET: Ethiopian Journal of Science Vol. 23, No. 1 (June 2000), pp. 35-51




Key words/phrases: Ethiopia, Gora Daget forest, soils, Welo highlands