Large herbivores maintain a two-phase herbaceous vegetation mosaic in a semi-arid savanna

Many arid and semi-arid rangelands exhibit distinct spatial patterning of vegetated and bare-soil-dominated patches.  The latter potentially represent a grazing-induced, degraded ecosystem state, but could also arise via mechanisms related to feedbacks between vegetation cover and soil moisture availability that are unrelated to grazing.  The degree to which grazing contributes to the formation or maintenance of degraded patches has been widely discussed and modelled, but empirical studies of the role of grazing in their formation, persistence, and reversibility are limited.  
We report on a long-term (17 yr) grazing removal experiment in a semi-arid savanna where vegetated patches composed of perennial grasses were interspersed within large (>10 m2) patches of bare soil. 
Short term (3 yr) grazing removal did not allow bare patches to become revegetated, whereas following long-term (17 yr) grazing removal, bare soil patches were revegetated by a combination of stoloniferous g...