Transition operations over plane trees

The operation of transforming one spanning tree into another by replacing an edge has been considered widely, both for general and geometric graphs. For the latter, several variants have been studied (e.g., edge slides and edge rotations). In a transition graph on the set T(S) of noncrossing straight-line spanning trees on a finite point set S in the plane, two spanning trees are connected by an edge if one can be transformed into the other by such an operation. We study bounds on the diameter of these graphs, and consider the various operations both on general point sets and sets in convex position. In addition, we address the problem variant where operations may be performed simultaneously. We prove new lower and upper bounds for the diameters of the corresponding transition graphs and pose open problems.