Prairies are fire-dependent. Before European settlement, prairies were part of a fire ecology. Wildfires ensured that these areas did not turn into forests. Historically, fires were set by lightning strikes and by Native American who recognized their benefits and intentionally started grassland fires. It is now widely known that fire is a natural process necessary for maintaining prairies by suppressing non-prairie plants, clearing dead plant material, and adjusting the nutrient balance in the soil in favor of prairie vegetation. After a burn, the blackened soil absorbs sunlight, which warms the soil and favors the regrowth of heat-loving prairie plants. When fire is suppressed, non-prairie species gain a competitive edge. The lack of fire is one of the main reasons why prairies are overrun with non-prairie plants such as woody shrubs and trees, which will eventually shade and kill the prairie grassland beneath them.
Fires tend to reduce the abundance of woody plants and promote herbaceous prairie plants. The suppression or reduction of periodic wildfires from prairies frequently invites the dominance of trees and shrubs to the near exclusion of native grasses and other prairie plants.
Fire is a natural component of the tall grass prairie and is fundamental in its formation and continuation. Periodic files eliminated tree seedlings and intrusive alien species. These fires can also help replace essential minerals and nutrients to the soil. Such fires may either be set by humans or started naturally by lightning. Typically, natural prairie fires are started every one to five years by lightening strikes. These fires moved rapidly across the land and did not penetrate into the soil. The fire killed the saplings and removed thatch, allowing for new growth. Historically, Native Americans used fire in the tall grass prairies to drive bison and improve hunting, travel, and visibility.
Today, prairie is being brought back in places using a land management technique borrowed from the Plains tribes: controlled burning. Spring fires clear out non-native grasses before the native grasses begin to grow. Fire also burns up dead plant debris on the ground, allowing the sun and rain to penetrate the soil, and releases nutrients, promoting growth and increasing seed yields.