Controlled burning of grasslands and forests has been used for thousands of years to stimulate plant germination, replenish the ground with valuable nutrients, thin out trees and burn dry pine needles and tree limbs on the ground. When humans were not intentionally setting fires, lightning strikes completed the job. http://green.blogs.nytimes.com/2012/09/26/burning-a-forest-to-save-it/?ref=earth
Article courtesy of The New York Times Green Blog posted by Glenn Swain