Conversations (XI) — to the empty space in the tree
Don’t tell me anything: You are the tree.
In a patch of years I forgot to climb
My life turned like a leaf stem.
Even in this fragile spinning
The memories of cicadas sing.
The underground sky feeds me.
Translations from the English 
What do you mean by the underground sky? This metaphor really makes me think…
Myths from all over the world speak of the realms beneath the ground as a secret hidden kingdom, as a dimension into which adventurous or unlucky travelers may find themselves. (The Norse myths Come to mind most easily for me.)
I won’t purposefully commit the intentional fallacy here and speak for the author, but there is another world entirely beneath the surface of the ground upon which we walk. For a tree, what grows in the sunshine is often less than half of its physical substance. Most of its world is subterranean, with growth and moisture and bacteria and insects all teaming in the darkness.
I touched upon something similar in a recent poem. You can find it here: http://wp.me/ppPSR-gV