Looks like you're using dandelO's 'Larch' tree. After going into the internals, you will find a Default shader. Under the 'displacement' try increasing the displacement shader just a little bit (in lieu of this, you could add a Displacement shader to the default shader). I'm not sure this will effect the trunk; but, you could give it a try,
This tree in nature does have a relatively smooth trunk. That is why I suggested to not go overboard with displacement.
