The part of the forest surrounding you now is like the teenager. This type of forest is comprised of early successional tree species such as Poplar, Hawthorn, Buckthorn and Birch. Much like a human teenager, this type of forest grows rapidly. It colonizes open areas so that other trees that require shadier conditions will be able to move in. These species are short lived and shade intolerant. When they die, they create plant litter on the forest floor, thereby providing nutrients that make soil conditions appropriate for secondary succession.
Image source: http://www.aucoeurdelarbre.ca/upload/images/1.3.2c_0400-pop-00111_1_1.jpg
Image source: http://www.pfaf.org/Admin/PlantImages/CrataegusMonogyna.jpg