Tenacity in a Midwestern Cornfield

On the wires crows sing their funeral dirge as the
Land below them drains its last movement.
The flatness of the geography mocks the mind with
Its barren drought, its shriveled cornstalks
Collapsing under the heat of errors.  Past mistakes
Shake their heads via zig-zag motions in the enduring
air;
Inspiration is a wasteland here, sapped as
Moisture by the already-dying soil as if failure
Is further needed
To prove to this withering thinking-place that giving
up doesn't cease with
Surrender, endings differ
From ends.  But the scenery crackles with just
One glance, the corn only have the memory
Of yellowing ideas long past gone
To grow for.  And isn't that enough?
Continuing to wait
When the waiting has already left you,
Keeping up with something in a
Field of nothing.
Standing guard at the doorway - 
Until you catch up with changing
And the change catches up with you.

Jennifer Tung's questions:

1. Do you think it is the visual imagery that drives the theme of this poem, or the theme that drives the imagery?

2. What is, in your opinion, the theme of the poem?

3. What overall tone does this poem project?

Thank you for reading!!