How is the movement up and down of the birches represented at different levels ?

How is the movement up and down of the birches represented at different levels 1) literally (the movement the speaker talks about), 2) structurally (how the poem is structured), and 3) symbolically (the meaning/symbol behind the movement) in the poem? Provide an example for each and explain how they contribute to the overall message of the poem. 1. Example and explanation: 2. Example and explanation: 3. Example and explanation.