AFK Tree farm.

Watch the video above for an introduction/how to use the farm.

This tree farm handles oak and birch trees perfectly.
It has a swith off lever, in case you get annoyed by the clicking of the dispenser.
It can, in theory supply it self with saplings using hoppers to collect them, but it probably can't be trusted to do this in 100% of the cases.
That's why there is a chest to stock up saplings in advance.
The farm also features a automatic axe dispenser, which renews your axe when the durability on it runs out.