There is only one tree on FamilySearch. You may have several family lines there but they are part of one tree.
I agree with everything Magnus said. And you don't know what other people or FamilySearch itself has added to the profiles you have in their tree.
I have families on FamilySearch and every week I have to check to see what other people have added to profiles I watch. It's not just people either, some of it is by FamilySearch itself.