Some troublesome trees on Main Street may have to be exchanged for ones that are not. Urban Forestry, a division under McMinnville Public Works Department director Bill Brock, has discovered a small problem with the shallow root systems of red maple trees that could create a big problem later.“Hank Patton is my lead in that division,” said Brock, during Tuesday night’s city board meeting. “He has talked to me about some problems we have downtown with some trees.