Lightening strikes would occur and burn a couple of acres up to hundreds of acres. Fires were also started by Native Americans to drive game, encourage growth of nuts, berries, seeds, etc., for food, improve pasture for domestic and wild animals, protect villages and camps, and to make travel easier. When the settlers arrived they tried hard to work the land, but it wasn't until the invention of the steel plow that the settlers were successful in breaking the sod. With this success came the disappearance of the prairies and the disappearance of the fires that the remaining prairies needed. Managing prairies with prescribed burns has many benefits.
Unburned prairies leave a mantle of dead and decaying vegetation.
This stifles the growth of the prairie plants and deprives plants of space and light. Plant diversity after a burn increases for 6 to 7 years and then the stifling growth once again occurs, but annually burned grasslands also creates small plant diversity. This is why burns commonly are done every 3-5 years. The burn also helps release the nutrients in the dead vegetation so it can be used by the new growth. The blackened soil heats up fast by absorbing solar energy, thus stimulating speedy seed germination, sprouting and growth.