ok, i will explain the poem. the solitary tree is the individual who stands alone for what he or she believes in while the government has worked to strike fear into the hearts of the general populace, hence "stands firm." the wheat (amber waves of grain) represents the rest of the american people, who have succumbed to their cowardice and are now yellow (as opposed to amber)and also contrast with purple (purple mountains' majesty)implying a lack of majesty. "waving in the wind" is in contrast with the firm resolve shown by the tree, meaning that the people allow themselves to be thrown to and fro acording to whatever events are currently transpiring. the next stanza describes a political "storm," relevant because of today's political turmoil. "sudden storms" can be interpreted as recent global events (I had 9/11 and the war in iraq in mind). the "crackling calm" is (to me at least), the period of tension between 9/11 and when the government took action. "thunder shakes and showers render/ heaven's lightning a fiery flare" evokes images of war and bombing (think back to the "shock and awe" campaign). cinders and sparks are the aftermath of the war, smaller and smaller bits of violence. the tree (individual) has been struck down, the casualty (not literally) of the war, his or her views have been tossed aside, destroyed. Still, the dignity that individual retains allows it to stand taller than the wheat (the rest of society), demonstarting that even after suffering a devastating blow, the individual's honor is greater than if he or she had conformed like the wheat.