To-do list:
1. Take two hours and read the entire thread
Help! I need legal advice re: easements . This will educate you in the fact that even though you are right, you may not win in the end.
2. Contact a surveyor and have the entire property lines staked, and have irons placed in the corners. Have the surveyors shoot lines to the tree stands and record them on the on the survey. Place a fence six feet in from the property line (to allow for maintainance), and have the surveyor record the fence line on the paper survey in relation to the property line. Mail a copy to the dufus neighbor.
3. Call the sheriff and report trespassing - insist that a report be written and obtain the report number from the sheriff. Often the police will try to get out of making a report, but insist on it being done. Document that the tree stands are indeed on your property.
4. Call the Game Warden/DNR as described in other posts.
5. Take pictures of everything. Start a log of dates/time/person containing every interaction and conversation you have regarding this matter. Keep copies of all letters, reports, surveys, etc.
6. Make sure that your property/fire insurance is up-to-date and is either a "replacement" policy, or the insured amount is adequate to rebuild.
7. The next time you're alone and talking to the neighbor, tell him your worried that, since you don't live there, things can happen to your property - but (with a true stare-into-his-eyes-non-blinking-make-no-mistakes-about-it manner) tell him that if something does happen it is amazing how similiar events seem to happen in groups. He'll know exactly what you're referring to.
8. Never make a threat that you're not ready to implement. People like your neighbor are bullies and are used to people being afraid of them and giving in without a fight.