Bush encroachment control demonstrations in southern Ethiopia: 1. Woody species survival strategies with implications for herder land management

摘要

We investigated six different bush encroachment control treatments on the responses of 29 woody species in southern Ethiopia. During the post-treatments (i.e. between June 2004 and 2005), we monitored tree stump total kill, partial kill and the responses of woody species to disturbances, in terms of coppicing and seedling regeneration. Protection from disturbance promoted seedling regeneration by 4.6%. The effects of tree cutting and fire greatly reduced woody species regeneration, while tree cutting and fire combined with grazing treatment was more effective in reducing coppicing. The fire and grazing methods were effective in reducing the regeneration of seedlings, although grazing alone had no effect. The effect of the tree cutting was comparable with tree cutting and fire, as well as tree cutting and fire combined with grazing on woody species regenerations. Overall, tree cutting and fire combined with grazing were more effective in suppressing the regeneration of encroaching species. We identified two major disturbance strategies. Some species invested in coppicing, while others invested in seedling recruitment. About 10% of the species were adapted relatively to either of the strategies. Only one of the 29 woody species was ranked among the top five in both of the two disturbance-adaptation strategies. The results have important implications for post-treatment management and public education.