Any where the trees have scars from bars or pedals, or the roots are becoming exposed. Better ways to slow riders down than forcing them between two trees. Around trees sure. There was one at the top of a crest that comes to mind. Everyone seems to happily go around it since the ground around it was cleared of sticks so you could.
Better to make rock gardens, divots in the ground or anything else to make riders slow down, or just design the track so you can't generate speed. Rock gardens take momentum without needing to brake, so would half berried long logs.
I'll go have another look, and let you know the locations, and happily discuss an alternative and build it if agreed on, and at the right time.
PM me if needed.