Background/Question/Methods
Evidence that human activity is influencing the earth’s climate is becoming increasingly apparent and these changing climatic conditions, along with altered atmospheric carbon dioxide concentration, are expected to have a substantial impact on future forest ecosystems.  Over the next 100-200 years, the primary impact of climate change on forests will be to alter the productivity of existing forests.  Forest productivity, the net primary productivity of forest systems, serves as a useful measure of ecosystem function under altered climates. 

Predicting future productivity is of particular interest in the northern Lake States where timber products are a significant component of the economy.  In addition, forests in this area occupy a “tension zone” where eastern hardwood forests meet both the boreal forest and grasslands.  Consequently, many tree species in this region are growing at or near their current range limits, and relatively modest shifts in climatic conditions may have substantial impact on forest productivity.  However, understanding how forest productivity will respond to climate change requires appropriately representing the interactions between altered temperature and CO₂.  Results/Conclusions

We utilized the PnET ecological simulation model to assess how forest productivity will respond to changing temperature and CO2 conditions in forests of the lake states region.  We have partitioned forests in this region into four types: aspen-birch, upland conifer, northern hardwoods and lowland conifers and have simulated productivity in each type for the next 100 years in several climatic scenarios.  Initial results indicate that the model accurately represents production variability between forest types, across climatic gradients, and through time. Our results suggest increasing productivity in all major forest types of the region, although aspen-birch forests appear more responsive than other types and all responses are highly sensitive to model parameters.  This work provides a foundation for more detailed examination of future forest productivity.