From roughly 1979 to 1989, a group of poets called the Misty Poets (Ménglóng Shi Rén) arose in post-Maoist China.
Zhao Zhengkai- better known by his nom de plume, Bei Dao- was one such poet.
Over the years Bei Dao traveled abroad and connected with literary groups in several countries. He happened to be in Germany when the massacre of Tiananmen Square occurred in 1989. Thought to have had a hand in those protests, or to have influenced them somehow, the Chinese government forced exile on our poet by denying his reentry into the country. Bei Dao, along with several other Misty Poets, have not been allowed back since.
That the river water alters the colour of the sky, which in turn alters our poet, signifies that this exile is an imposition on our poet's freedom (represented by the sky), and that this imposition deeply pains (or alters) our poet, as we'll soon see.
The narrator desperately desires to reach the other bank, so much so that he stands there at the river's edge and sees his shadow 'like a tree struck by lightning', indicating the poet's depth of pain. He again, and almost mournfully, reiterates his desire: I want to go to the other bank … but the river and its current (his exile) prevents him.
Finally, in the last stanza, the poet sees the trees on the other river bank. Just as the tree struck by lightning (line 6) represented the poet and his depth of pain, so too the trees on the other bank represent people- and because the other bank represents China, the trees represent his countrymen from whom he's exiled.
And there you have it, my interpretation of Bei Dao's poem, The Boundary. That this is what the poet intend I am highly doubtful- as I mentioned, the poem is said to have been written between 1970 and 1986, prior to him being exiled in '89. Nevertheless, this was the first impression I derived from it, and so I remain faithful to it. I would so love to know your interpretation of it.
Thank you for stopping by. And Bei Dao, happy birthday, my friend ...