5 years ago

Die Wirksamkeit von Boden

Die Wirksamkeit von Boden

Study area and general

Study area and general methodology Figure 3.2 Agro-ecological map of North and South Wello zones Topography The digital elevation model (DEM) reveals that larger parts of Wello are characterized by rugged topography that consist very high mountains, deeply incised canyons and gorges, valleys and plateaus (Figure 3.3). The rugged topographic condition of the area was also reported in other studies (e.g. FAO 1984; Tefera et al. 1996; Coltorti et al. 2007). Due to the strong relief differences, anthropogenic activities have led to extensive degradation. The highest (4220 m) and lowest (900 m) elevations are in the South Wello zone. The lowest areas are in the Rift Valley, which is part of the East African rift system. The DEM analysis also indicates that the areas covered by slopes < 2%, 2 to 15%, 15 to 30% and >30% cover 2%, 30%, 28% and 40 % of the total area, respectively. Land with slopes less than 15% is most suitable for agriculture (Hurni 1988). However, this area accounts for only 32% of the total area. 24

Study area and general methodology Figure 3.3 DEM slope map of the North and South Wello zones Geology Wello is covered by Cenozoic volcanic rocks with some sedimentary rocks (Figure 3.4). The Cenozoic volcanic rocks have developed from tertiary flood basalt sequences with intercalation of felsic lava and pyroclastic rocks up to 3 km thick. The Cenozoic volcanic rocks and the associated sedimentary rocks are further subdivided in various formations. The major formations are Ashangi, Tarmaber-Megezez, Alajae, Aiba basalts and Amba-Aradom formations covering 49%, 18%, 14%, 12% and 3%, respectively (Tefera et al. 1996). 25

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