Here's why:

* Wide area: Prairies are vast, expansive areas of land.

* Grainland: Prairies are often characterized by grasses, which are a type of grain.

* Without trees: Prairies are treeless, or have very few trees.

Other possibilities could include:

* Steppe: Similar to a prairie, but found in drier climates.

* Savanna: Has grasses but also scattered trees.

Do you have any more details about the location or specific features of this area? That might help narrow it down further.