Effectiveness of exclosures to restore degraded soils as a result of overgrazing in Tigray, Ethiopia

摘要

As a response to land degradation in Tigray, Northern Ethiopia, regional authorities have promoted rehabilitation of degraded lands through closed areas since 1991. It is generally assumed that exclosures lead to restoration of natural resources such as soil fertility, vegetation biomass and composition, fauna, and water storage; however, this is not supported by studies. In the present study, our objective was to assess the impact of exclosures on soil properties, and relate the age of exclosures to their effectiveness in improving soil chemical and physical properties. Five and ten years closed areas had significantly (p < 0.05) higher levels for soil organic matter, total nitrogen, and available phosphorus compared to free grazing lands, and the highest levels in were observed in closed areas at footslope position. Our results show that exclosures are not only effective in restoring vegetation, but also in improving soil nutrient status, and reducing erosion. From a technical point of view, it is therefore recommendable to convert grazing areas into exclosures. However, implementing exclosures leads to an even smaller communal area left for grazing and the socio-economic consequences of this should also be considered.