Extended Rotation Forests. Forest stands for which the harvest age is increased beyond the optimum economic harvest age [e.g., increasing the harvest age of an aspen stand from 40 years (i.e., the "normal" economic harvest age for aspen on most sites) to 50 or 60 years] to provide larger trees, wildlife habitat, and other non-timber values. Additional detail on the management of ERF on DNR-administered lands are contained in DNR Extended Rotation Forest Guidelines (1994).