Sumacs will take over if you let 'em. They're nicer about it than the multiflora, but they're just as determined. Happily, it's pretty easy to pull 'em out by the roots. The roots snake all over the land, and the process would make me sad if we had a "lawn" or anything that we're growing on purpose, but for now, it's all good.
Hail the conquering hero: