ORIGIN AND EARLY DEVELOPMENT OF NORTHERN WHITE-CEDAR STANDS IN NORTHERN MICHIGAN

Stem analysis was used to reconstruct establishment and development pa tterns of seven mature northern white-cedar (Thuja occidentalis L.) st ands in Michigan's Upper Peninsula. Stands originated after single or repeated disturbances, probably timber harvests, that occurred between 1870 and 1935. These disturbances were essential for successful cedar recruitment into the overstory. Stands developed as single or multipl e cohorts, depending upon the severity and frequency of disturbance. D uration of the establishment period following single disturbances rang ed from less than 10 years to 50 years. Seedlings in some multiple coh ort stands established almost continuously for 100 years. Cedar overst ory trees, saplings, and seedlings that survived disturbances exhibite d highly plastic height growth responses to suppression and release. A ll study areas developed stand initiation and stem exclusion stages. O nly 3% of all stems greater than or equal to 2.54 cm DBH established a fter 1945. Cedar germination beneath the mature canopy was abundant, b ut cedar seedlings taller than 30 cm were completely absent from most sites. Successful cedar establishment and recruitment following the in itial wave of timber harvesting contrast with widespread regeneration failures after present-day cutting practices. Factors influencing the cedar recruitment process have apparently changed over the past centur y.