Hydrology and microtopography effects northern white-cedar regeneration in Michigan's Upper Peninsula

Many harvested northern white-cedar (Thuja occidentalis L.) sites have not regenerated to cedar but have become dominated by other species such as balsam fir (Abies balsamea (L.) Mill.) and tag alder (Alnus rugosa (Du Roi) Spreng.) A regenerating cedar fen near Escanaba, Mich., was used to study factors related to regeneration success and failure. Twelve plots (6.1 X 6.1 m) were established on the site to collect data on hydrology, microtopography, stand composition, and stem density. Abundance of cedar regeneration was positively correlated with percentage of hummocks. There were more cedar on microsites with drier conditions (numerous hummocks) while more shrubs and hardwoods were found on the wetter areas (fewer hummocks) of the fen. The shallow depth to groundwater and unsaturated soil thickness early in the growing season are suggested to be factors.