Tough to say what to do. The "correct" answer is to find the landowner or land manager, and work with that person. You might get away with clearing sticks and small brush. I would try to find out more about the trail and the ownership before going big guns with chain saw or anything like that.
Do you know other riders in the area? A good start might be to quietly ask around to learn more about the trail and how it's managed, if it's managed.