Fire has been an important natural part of tallgrass prairie ecosystems, started by both lightning and American Indians. Production of vegetation on burned areas can be double that on unburned, unmowed, and ungrazed areas where the old standing dead vegetation is deep. Burning stimulates earlier plant development than on unburned areas. In tallgrass prairie, burning stimulates flowering of warm-season grasses and increases stem density. Late spring burning results in fewer forbs but greater grass production than fall or early spring burning. Up to at least six years, above ground biomass is positively related to the number of years between burning. In Kansas, at least, burning is effective in keeping out exotic plants where the prairie grasses are vigorous. The few studies of fire effects consistently indicate that neither the ash left from burning nor heat form fires affects production. Warming of the increased growth resulting form burning. The increased light for new growth by removal of the old plants seems to be more important