What are the symbols of land, river, wind and dawn in Ai Qing's I Love This Land?

Before "land, river, wind, dawn", the poet deliberately added adjectives or modifiers with emotional color, and turned them into symbolic and suggestive pictures, which not only hinted at the troubled fate of the motherland, but also hinted at the indomitable people and the hope still growing on the earth, and hinted that the poet should make every effort to sing for them with fate. Even if you die, you should bury yourself in this land and enrich it with your body. From the perspective of conception, the poet still sticks to the virtual image of "bird" ("even feathers rot in the land"), which makes a strong contrast between life and death, and shows the bird's persistence and sincere love for the land in the comparison, thus artistically shaping the image of a singer who is loyal to the land.