Wisconsin's northern forest communities are found north of the vegetative Tension Zone, an area of climatic transition where the prairies and oak savannas that historically dominated southern Wisconsin changed to mixed deciduous-coniferous forests. Today, vegetation still changes along the Zone, but the transition is largely from agricultural uses to a more continuous forest cover. The shorter growing season in northern Wisconsin, away from Lake Michigan, makes this area less suitable for agriculture and allows forest to predominate.
Forest ecosystems were drastically disturbed between the 1850s and early 1930s when nearly all of the primary forest was harvested or burned during the Cutover. Pine logging began near large rivers as early as the 1830s. Starting around 1870 and continuing into the 1920s, fires had a major effect on the northern forest, occurring with greater frequency and intensity due to "slash" left from logging. By the turn of the century, pulp mills were constructed to utilize the less-desirable wood, beginning the gradual switch to a pulp-dominated industry. Public reaction to the abuses of the Cutover resulted in legislation and government programs designed to rehabilitate the impacted forests.
Data from the Forest Inventory and Analysis Program indicate that in 1996 there were approximately 10.9 million acres of forest north of the Tension Zone, covering 58% of the area. Northern forests make up 69% of the total forested area statewide. In 1996, maple-basswood was the most common forest type group in the northern forest, followed by aspen-birch. Lesser components included the oak-hickory, spruce-fir, pines and lowland hardwood groups.