Perhaps the tree symbolises a person, so change for one person then affects 3 other trees, so three other people?
I don't think it is a bad thing, it is change, but then some changes are painful.
While I was reading, I thought of Autumn, the leaves fall but the trees do not die, the trees in the spring come alive with new leaves so it is a
cycle, a beautiful one but I just wonder how the trees feel during Autumn?