The central plains of North America, a wide swath from the Texas coast north to Saskatchewan, Canada, were once vast grassland, the prairie. The climate there is too dry to support trees, except along rivers. From west to east, there is a transition from the more desert like short-grass prairie (the Great Plains), through the mixed-grass prairie, to the moister, richer, tall-grass prairie. This change is related to an increase in rainfall from west to east. Grasses shorter than 1.5 feet (0.5 meter) dominate the short-grass prairie. In the tallgrass prairie, some grasses grow to more than 10 feet (3 meters). Colorful wildflowers brighten the prairie landscape.
Grassland soil is the most fertile in North America. Instead of wild prairie grasses, this land now supports agriculture and the domesticated grasses corn and wheat. The tall-grass prairie, which had the best soil in all the grasslands, has been almost entirely converted to growing corn. Much of the grassland that escaped the plow is now grazed by cattle, which has disturbed the land and aided the spread of invasive, normative plants.
Other outlying grasslands occur in western North America. Between the eastern deciduous forest and the prairie is savanna, grassland with scattered deciduous trees, mainly oaks. Savanna also occurs over much of eastern Mexico and southern Florida.
See also: Eastern Deciduous Forest, Scrub and Desert, Tundra, Coastal Vegetation
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