This is necessary in sandy soils where water is quickly absorbed and stored many feet underground. Root systems also store energy which produces new growth. This helps the plant endure extreme conditions such as a harsh winter or a fire. Growth of prairie grass is stimulated with prescribed burning. Spring fires set back non-native grasses before the latter native grasses begin to grow.
Fire also burns up dead plant debris on the ground allowing the sun and rain to penetrate the soil.
Also, fire releases nutrients that promote growth and increase seed yields.