Analyzing Atmosphere through Diction

Read the following passage from a fictional narrative:

"The old oak tree stood solitary and proud in the center of the meadow, its leaves whispering secrets to the gentle breeze. Time passed slowly here, as if the world beyond had forgotten its busy ways. Children laughed and played beneath its sturdy branches, while the sun filtered through an emerald canopy, creating patterns of light and shadow on the soft grass below."

How does the author's choice of words in this passage enhance the overall atmosphere of tranquility?