This is a talk given in Flagstaff, Arizona to the School of Forestry on 18 April 2007. It explains six basic models that can explain plant diversity in landscapes at different scales. The same models can be used to better manage landscapes to maintain plant diversity. The models include the intermediate diversity model developed by Phil Grime, and the centrifugal model developed by Paul Keddy. Most of the examples come from wetlands, but they can be applied to terrestrial vegetation as well. The general point is that plant diversity can be explained and manipulated with a small tool box of pragmatic models.