Eastern woodlands of the United States

The eastern woodlands of the United States covered large portions of the southeast side of the continent until the early 20th century.

The coastline later changed during glacial melt, both in the Mississippi River valley and sea level rise of 130 meters (430 ft).

[6] Humans arrived as five thousand years passed following the retreat of the glaciers, while deciduous forests expanded northward throughout the region.

Broadleaf evergreen and pine forests occupied an extent similar to their current one, primarily in the Atlantic Coastal Plain.

Mixed hardwood forests dominated the majority of the upper Coastal Plains, Piedmont, and lower mountain regions.

Southern pine communities dominated the middle and lower Coastal Plains, whereas evergreens and some remnant boreal elements occupied higher elevation sites.

Extensive expansions of prairies and woody grasslands occurred throughout the region, and xeric oak and oak-hickory forest types proliferated.

Cooler-climate species migrated northward and upward in elevation; many vanished from the region during this period while others were limited to isolated refuges.

As a result, elements of the prairie flora became established throughout the region, first by simple migration, but then also by invading disjunct openings (including glades and barrens) that were forming in the canopy of more mesic forests.

[6] After the end of the optimum about 5,000 years BP, as the climate cooled and precipitation increased, species migrated so that communities were reassembled in new forms in which all of the components of the modern southern forests were in place.

Intentional burning of vegetation was taken up to mimic the effects of natural fires that tended to clear forest understories, thereby making travel easier and facilitating the growth of herbs and berry-producing plants that were important for both food and medicines.

[1][6][7] The practice was so common that a North Carolina law in the early 18th century required annual burning of pastures and rangelands every March.

Overgrowth shades and stunts longleaf pine seedlings, undergrowth increases, and succession creates the southern mixed hardwood forest where savanna used to be.

Intentional use of fire to manage vegetation began to be accepted again after World War II, and at present about 6,000,000 acres (24,000 km2) a year are burned.