Between the prairies of the Great Plains and the forests of eastern North America, there was once a great transition zone composed of a shifting mosaic of prairie, savanna, and forest. Prior to the fire suppression that followed settlement, southern Wisconsin was dominated by oak savanna. Somewhat surprisingly, until fairly recently Wisconsin's plant ecologists paid little attention to these communities, dismissing them as merely prairies with trees. In the 1990s, several ecologic studies were initiated, partly spurred by restoration activities. Here, I will review work by others and myself into the horizontal patterning of savanna vegetation. Environmental gradients of soil and light strongly influence community patterns, with soil having the stronger influence. The physiological mechanisms are suggested by the distribution of plant traits, but little direct physiological study has been done. "Restoration experiments" provide crucial information lacking from studies in remnant communities and provide useful informal learning opportunities for volunteers and students.

Key words: ecological restoration, light gradient, oak savanna, soil gradient, vegetation pattern, Wisconsin