Olson and Richards assessed the spatial arrangement of tiller replacement on grazed and ungrazed tussocks of Agropyron desertorum. In both ungrazed and grazed areas, replacement tillers tended to be oriented on the outside perimeter rather than in the core of the plants, possibly due to increased resource and light availability in this area. Heights of replacement tillers on the perimeter or within the core seldom differed. Greater tillering on the perimeter than within the core indicates that the tussocks were expanding. Apparently, grazing neither enhances tussock expansion and subsequent disintegration, nor does it necessarily lead to patches of tillers within tussocks of A. desertorum. Olson and Richards conclude that although grazing did not directly affect the spatial arrangement of tiller replacement, it reduces tiller replacement and thus tiller densities within tussocks of A. desertorum, thereby indirectly leading to tussock thinning and disintegration.
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