What is the function of the natural scenery mentioned in the poems of Long Songs (Han Yuefu)? What kind of truth does the ending of this poem tell us?

This poem begins with "Sunflowers in the Garden", and then the water flows to the sea and never returns, indicating that time is like running water and never returns. Finally, we should persuade people to cherish their youth and work hard, and don't wait until they are old to regret it. This poem uses things to express meaning. First, it uses the sunflower in the garden as a metaphor. "Green" means it is flourishing. In fact, under the sunshine and rain in the whole spring, everything is scrambling to grow. Why is this happening? Because they are all afraid that autumn is coming, they all know that autumn wind will wither a hundred herbs. The rhythm of life in nature is like this, and so is life? If a person doesn't work hard when he is in a good time, it will be too late to regret when he is old. This poem thinks that life is fleeting from the beautiful scenery of youth in front of us, and encourages young people to cherish time, make warnings and inspire people to forge ahead.