What is Pre-Columbian savannas of North America?

Pre-Columbian savannas of North America, consisting of a mixed woodland-grassland ecosystem, were maintained by both natural lightning fires and by Native Americans before the significant arrival of Europeans. Although decimated by widespread epidemic disease, Native Americans in the 16th century continued using fire to clear savanna until European colonists began colonizing the eastern seaboard. Many colonists continued the practice of burning to clear underbrush, reinforced by their similar experience in Europe, but some land reverted to forest.