You can access all of Yokmir Forest from the moment you enter. You can even jump off the cliff to enter Yokmir Cave though you will most likely die from one hit of an orc down there.
Defeating the orc(s) at the entrance will cause a treasure chest to spawn, which contains a Small Shield.
In the dead end area below the first room with ants, is a chest containing Leather Boots.
The second ant room's chest contains 4x Turnip Seeds