In the northeastern US, this is primarily "natural" regrowth. It's still probably a different mix of trees, but it is a mix, of soft and hard woods. The north

In the northeastern US, this is primarily "natural" regrowth. It's still probably a different mix of trees, but it is a mix, of soft and hard woods. The northeastern US wasn't just logged, it was cleared, primarily for pastureland, and that primarily for sheep. Between cotton, synthetic fabrics, and cheap grazing land out west, it stopped being economically viable, so a lot of northeastern farmland was just abandoned. Over the next ~century, trees took over the once-clear pastures. Now you've got great swaths of woodlots with laboriously constructed stone fences throughout them.