"The tree" refers to the red willow tree. Because the red willow grows at an average altitude of 5,000 meters on the plateau, in that natural environment is very harsh in the highland desert, there is no other trees survive.

"The closest tree to the sun" describes the red willow's calm and relaxed demeanor in the face of "cold and lack of oxygen," vividly demonstrating the red willow's tenacious vitality.

The article reveals the beauty and power of the red willow and the narrative of excavating the red willow, showing the author's passion for nature and life and his pain at the destruction of the ecological environment by mankind.

Expanded Information

The article is titled "The Green Tree Closest to the Sun", which has two meanings: the surface meaning is that the red willow grows on the plateau with an average elevation of 5,000 meters, and it is the tree "closest to the sun"; the deeper meaning is that the red willow grows in the highland with an average elevation of 5,000 meters. "The deeper meaning is to show that the red willow overcomes the harsh natural environment of the growth of the momentum, highlighting the red willow has the tenacity of life and great power.

The closing paragraph of the article used two rhetorical questions, the deep meaning is to tell people that the red willow is the earth's "aboriginal", but mankind has destroyed it, implicitly expressed the author of the people to destroy their own living environment worries, calling people to love nature, cherish life, and to protect the living environment of the awareness of worry.