Symbolism of the Tree's Transformation

In literature, symbolism is a powerful device used by authors to convey deeper meanings and themes through objects, characters, or actions that represent something beyond their literal sense. Consider the following excerpt from a fictional short story:

"As the last leaf fell from the tree, the chill of winter crept into the air, signaling the end of the vibrant season. The tree, once full of life, now stood barren and skeletal, casting long shadows over the ground where flowers once bloomed."

What does the tree's transformation primarily symbolize in this excerpt?