Conversion of communal grazing lands into exclosures restored soil properties in the semi-arid lowlands of northern Ethiopia.

摘要

In the semi-arid tropics, communal grazing lands provide a livelihood for millions of people. However, it is highly threatened by overgrazing and continuous land degradation and, as a result, proper management is important to improve the livelihood of the people. This study investigated the effectiveness of exclosures established on communal grazing lands to restore soil properties and identified the relationship among soil properties, site and vegetation characteristics, and exclosure age. A space-for-time substitution approach to detect changes in soil properties following the establishment of exclosures on communal grazing lands was used. Replicated (n=3) 5-, 10-, and 15-year-old exclosures were selected and paired, each exclosure with an adjacent communal grazing land. All exclosures showed higher soil organic matter (OM), total soil nitrogen (N), available phosphorus (P), and cation exchange capacity (CEC) than the adjacent grazing lands. The increases in soil properties between exclosures and grazing lands in the 0- to 0.2-m depth varied between 58 and 101% for OM, from 54 to 108% for N, from 26 to 128% for P, and from 18 to 28% for CEC over the grazing lands. Soil properties in exclosures and grazing lands showed significant (p<0.05) correlations with biomass and vegetation cover indicating that vegetation restoration is a key to restore degraded soils through exclosure establishment. Establishing exclosures on communal grazing lands can be effective in restoring the degraded soils in the semi-arid lowlands of Ethiopia. However, further studies are required on the ecological and economic benefits of future exclosures, as expansion of exclosure could cause grazing pressure on the remaining communal grazing lands.