What type of grasses dominate in an area where grazing is heavy or overgrazing occurs?

short-grass, unpalatable ruderal and shrubs species.

Explanation:

Overgrazing can be defined as the intensive grazing of farm animals in a restricted area of land, usually over a long period of time. During this period, there is no recovery rate for emergence of newer species. Effects of Overgrazing reduces the  usefulness, productivity, and biodiversity of the land and is one cause of desertification and erosion.

In an area where grazing is heavy or overgrazing occurs, short-grass species usually less than 2-3 inches tall exists in the overgrazed areas. In other parts of the world, overgrazed pasture is typically taller than sustainably grazed pasture, with grass heights typically over 1 meter and dominated by unpalatable ruderal and shrubs species.