As older forests dieoff, new ones dominated by sugar maple, red maple, beech, ash, or elm often take their place. Historically these shade-loving species were limited to moist, cool, valleys, or lowlands where they cast a deep shade. Today they are moving into oak-hickory woodlands, often migrating up hillsides from lower, moister, areas. Like a yard too shady to grow a lawn, the deep shade that sugar maples cast can suppress oak-hickory regeneration and eliminate wildflowers in uplands.
In North America, oaks and hickories are keystone species. They are the key to the survival of many other plants and animals. Their nuts are food for turkey, squirrel, deer, and many others. The most diverse part of the forest, the ground floor, contains dozens of native wildflowers adapted to live underneath their canopy. Their leaf litter provides