The last two types represent successional change after a disturbance. Groundlayer species are evenly divided between spring and summer bloomers. Dry to wet, clay to sandy loam. Gray Wooded and Podzol. Northernmost stands are very stable.
Southern stands tend to be replaced by northern mesic forest.
Depends on continuing disturbance, such as fire, insect attack, and windthrow to maintain itself. Without disturbance, a boreal forest degenerates rather than develops. A fire burns the thick, acidic litter layer, releasing nutrients and allowing seedling regeneration. Minnesota, north to limit of hardwoods in Manitoba and Ontario. Boreal fingers down into the Appalachian and Rocky mountain ranges and along the West Coast.