While (whilst??) looking for details of Le Prieur rocket mountings to reply to another thread, I found a photo (Over the Front Vol 2 Number 2 Summer 1987, p.175) that depicts a close-in Drachen defense Parabellum (so captioned ) & gunner with the gun mounted on what is clearly a tree with limbs cut off, or the post made from such a tree driven in to the ground.
Hth, Rob