This species has certainly become more common since pre-settlement times when fire restricted plants to high cliffs and blufftops.  Since the suppression of fire, red cedar has readily invaded open dry areas, especially dry prairies, and led to succession in these habitats.  In the Driftless Area, high ridgetops with scattered, large, old oaks and understories of thick red cedar and oak saplings are a common sight and are a good example of this landscape change.  The cedar glades of Curtis (1959) are different from the cedar glades of the southeastern United States.  The former are better called cedar thickets and are probably the result of fire suppression rather than a unique community.  Open patches within the thickets often still support dry prairie species, attesting to their past status.  These habitats are restricted to rocky bluffs, cliffs, and areas along major rivers where natural firebreaks existed.  Eastern red cedar occurs mostly south of the Tension Zone and seems under-collected in some counties; it is native in a few areas to the north, such as the alvars of Brown Co.  Wisconsin’s oldest known tree is an eastern red cedar, growing on the Niagara Escarpment, that is over 1,300 years old.