A multi-landscape comparison of potential climate futures in Minnesota and Michigan

Background/Question/Methods

The forests of the Great Lake states are unique ecosystems along the temperate - boreal forest transition zone. Within the northern Midwest, the Boreal Hardwood Transition ecological region covers almost 55 million acres.  The current disturbance regime is largely driven by harvesting. The arrowhead region of northeastern Minnesota and the northern lower peninsula of Michigan provide two examples of northern Great Lake forested landscapes that represent a range of unique forest types and conditions.  Over the next century, the pace of climate change is projected to exceed the rate of natural adaptation or adaptation via traditional forest management. This lag may result in tree species extirpation, loss of forest structure, productivity, species diversity, and a decline of ecosystem resilience.  Our objectives were to assess the resilience of forests in the northern Great Lakes region to climate change and considering current forest management practices.  Specifically, we addressed how climate change will affect northern forests in northeastern Minnesota and northern lower Michigan, how the response of the two systems differ, and why.  We used a forest landscape simulation model, LANDIS-II, that integrates succession, disturbance, and climate change.  We simulated two climate emissions scenarios over 150 years.

Results/Conclusions

Our simulations indicate substantial, although different, responses across the two landscapes.  Landscape simulations resulted in an initial increased total above ground biomass in both Minnesota and Michigan under all climate scenarios.  The capacity for increased growth is likely due to the history of intense timber harvesting throughout the Great Lakes region over the last century. Future forest growth includes landscape scale recovery and an overall increase in biomass for all climate scenarios.  After 30 years however, the A1FI climate scenario resulted in a departure from the B1 and current climate scenarios within both landscapes.  The northeastern Minnesota biomass under the A1FI climate responded after 100 years with a substantial increase in biomass.  In contrast, the northern lower Michigan biomass under the A1FI climate resulted in a continual decline throughout the simulation.  Likewise, the B1 climate scenario in Michigan resulted in a plateau and slight decline in biomass after 100 years compared to Minnesota where the B1 climate scenario continued to produce biomass that exceeded the current climate scenario at the end of the simulation.  There was also large variation among species and forest types.