A question of ownership
 

I would appreciate some help with regards to what appears to be another strange Spanish system.

We bought our house 4 years ago (it is a chalet in the campo) and at the time we were told that although we owned the house and land we did not own the ancient olive tree that stands in its grounds. Sure enough, 3 years ago on Boxing Day we arrived back to find two people in our garden collecting the olives, trampling over my good wife´s newly dug soil in the process!! They have not been again since.

I am sure I have read somewhere about something similar happening to others and the article stated that if they do not come and do the same again in a period of 3 years, the tree will revert to our ownership. If true, I am not sure how to go about this. Nothing shows on the 'escritura' and shows us as having all rights.

Here's hoping one of you can assist.