You can make them with Buildcraft as well. Using an on/off switch. Had a great one on Industrial Rage. It used a filler to harvest the trees and a builder template to plant the saplings. Simple water transport and obsidian pipe to collect, then wood sorted to chests and sapling re-sent to the builder.
Finally, a simple redstone circuit to power them.
Can't remember who made it (think it was Superzip), but it was very clever.
This is why I love IC²+BC.