The chapter opens with a description of the river of life that proceeds or flows from the throne of God inside the city where Christ is on the throne (v.1). On either side of the river was the tree of life (v.2). This is the same tree that was in the Garden of Eden.
Genesis 2:9 And out of the ground made the LORD God to grow every tree that is river pleasant to the sight, and good for food; the tree of life also in the midst of the garden, and the tree of knowledge of good and evil.
There also was a river that ran out from Eden.
Genesis 2:10 And a river went out of Eden to water the garden; and from there it was parted, and became into four heads.
The correspondence is very strong. You can see the connection between the paradise of the initial creation and the paradise of the final heaven on earth.
I believe also that the tree of life is symbolic of Jesus Christ, who is the source of life to all who believe. “In Him was life” (John 1:4).
Proverbs 11:30 The fruit of the righteous is a tree of life; and he that wins souls is wise.
Christ is the fruit of the righteous, as only God is righteous. In Christ is the only way we can be fruitful to win souls. The Lord also says: