How does expansion of bush encroachment affect soil carbon sequestration and soil greenhouse gas carbon dioxide emissions in the Borena pastoral system, Ethiopia?

The Borana rangeland, Southern Ethiopia was productive grazing areas. However, bush-tree cover has become dominant in the rangeland mainly due to fire band and climate change. How does the expansion of bush encroachment affect soil carbon sequestration and soil greenhouse gas carbon dioxide emissions? Does it provide benefit for soil fertility and global climate through increasing soil carbon sequestration? Or does it provide problems for soil fertility and global climate through decreasing soil carbon sequestration and increasing soil carbon dioxide greenhouse gas emissions?

 Photo source: http://savingstripes.wildlifedirect.org/category/rangeland-management/