What is the 'tree of worldly existence' and how is this metaphor explained in Chapter 32?

Chapter 32 describes the 'tree of worldly existence,' or samsara, using a powerful metaphor. This tree is said to be very extensive, encompassing everything from the unmanifest to the immovable. It is characterized as being filled with birth, death, and sorrow, and is ultimately perishable, which is why it is called a tree (subject to cutting and destruction). Uniquely, as mentioned in Chapter 32, this tree has its roots above, and its branches spread immeasurably, making it difficult to comprehend. While it may appear pleasant from a distance, the text warns that when one tries to embrace it, thorns will pierce their whole body.