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SEDIMENT YIELD AT SOUTHWEST ETHIOPIA’S FOREST FRONTIER [Abstract ID: 0610-03]
Deforestation is one of the major factors of soil erosion in tropical regions, but to what extent does crop growth in deforested areas protect the land from erosion? We evaluated the effect of deforestation on suspended sediment yields on the scale of zero-order catchments by contrasting five paired small forest and cropland catchments at Ethiopia’s southwestern forest frontier. Suspended sediment samples were collected from nine San Dimas flumes and one V-notch weir installed in catchments draining the natural forest and cropland, at different altitudes. The suspended sediment data were collected from June 8 to October 30, 2013 and 2014. The suspended sediment yields of both land-use types was strongly correlated with the corresponding discharge. The results show that the average seasonal suspended sediment yields from cropland (17.0 ± 7.6 Mg ha-1) is four times higher than from the paired forests (4.0 ± 1.9 Mg ha-1). High sediment yields from forests are related to livestock grazing, but forests still have an important role in protecting the surface soil from erosion on south-west Ethiopia’s forest frontier. Land management in southwestern Ethiopia’s highlands will need a big change in paradigm, in which the dominant belief in the recently imported mahrasha ard plough is abandoned, oxen and other cattle reduced in number and kept in the homestead, the forests better protected from human and livestock interference, and the open farmlands turned into agroforestry. Such an approach is still possible as all the elements required are available in the landscape.