You mentioned that you're going to speak with the owner soon. RECORD THE CONVERSATION. If he admits that he trespassed and chopped down your tree, you've got it recorded. His tone of voice will also be documented. It is legal to record conversations as long as one party (yourself) knows - meaning, you don't need to let your neighbour know that you're recording him.
I can't stress enough how important it is to have good documentation and records of everything. It will come in handy if you ever need it - for litigation, police report, etc.
GOOD LUCK OP