What happens to the trees in autumn?
Their leaves fall off. Except on Evergreens as their leaves never fall.
Most deciduous trees lose their leaves in Autumn . . . trees like maples, linden trees, elm trees; however, oddly enough, many oak trees do not lose their leaves in Autumn. The leaves turn colors, and then die and turn brown. The dead leaves take their time to drop off. In my area, some oaks still have their dead leaves as late as early Spring.