Stand development in a 130-year-old spruce-hemlock forest based on age structure and 50 years of mortality data

Abstract

Influences on forest stand development were assessed using tree age and long-term mortality data in ten 0.4 ha permanent plots established in 1935. The stand originated following a major fire in the 1840s with a period of rapid invasion (1851–1870). This was followed by slower filling to full stand closure (1871–1900), recruitment suppression (1901–1930), reinitiation of hemlock recruitment (1931–1950), and continued slow recruitment (1951-present). Recruitment re-initiation was apparently associated with natural stand thinning and not with major disturbance. Large blowdown patches occurred in two plots in the 1960s, but the primary effect was release of hemlock advance regeneration rather than recruitment of new individuals. From 1935 to 1983 annual mortality (calculated from 5–10-years remeasurements) was 0.5–1.2% for both species. At this rate, continued thinning will likely allow a gradual transition to an all-aged forest, as population turnover time is short relative to frequency of intermediate or major disturbance.