The Great Plains ecoregions can be classified into 4 types based largely on precipitation:

• Short Grasslands occur where annual precipitation is less than 400 mm.

• Mixed Grasslands take over where annual precipitation reaches up to 600 mm.

• Tall Grasslands thrive where annual precipitation can accumulate up to 1000 mm.

• Woodlands and Savannas occur in pockets of low-lying land where soil moisture supports trees.