Increasing atmospheric carbon dioxide concentration alters forest stand development, so do management guidelines need revision?
Building off of the Aspen Free-Air Carbon Dioxide Enrichment Experiment (Aspen FACE) in Wisconsin, Forest Service scientists are studying forests in northern Wisconsin to find out if forests may already have undergone developmental changes in response to increased carbon dioxide in the past century. The researchers grew pure and mixed stands of trembling aspen for 11 years in either present-day (360-380 parts per million) or elevated (560 parts per million) carbon dioxide and found compelling differences in stand development. Stands in elevated carbon dioxide grew faster and had developmental trajectories of self-thinning communities that carried more basal area at equivalent trees per acre. Comparison of the Aspen FACE stands to historical data suggests that current stocking guides underestimate maximum carrying capacity. In many situations, data used to develop currently employed stocking equations are in excess of 80 years old, when atmospheric carbon dioxide was 33 percent less than today’s 408 parts per million. Given that nearly every silvicultural practice is founded upon principles of stand development and size-density relationships, comprehensive reassessments may be needed because of atmospheric changes that have already occurred. To verify the experimental findings, field crews completed the first phase of surveys of pure and mixed trembling aspen stands on the Chequamegon-Nicolet National Forest. These assessments will be analyzed for their developmental characteristics for comparison to historical data.
Forest Service Partners