You do not want trees on your pond dam. I've written about it and recorded radio shows on the topic, but never actually followed through on my own pond. Tree roots can destroy the structure of dams and cause leaks. You can see from the first photo that we had a lot of trees on our dam. Not now. A bulldozer popped them out yesterday. It looks very barren and almost sad down there, but it's for the best. We still have wildlife habitat on three sides of the pond.
BEFORE (Bob was teaching Caroline how to drive, so this was about four years ago)
AFTER (looking west, with our barn on the hill)
Pond overflow on south side of dam. We cleared the brush and added rock.