1 Dendroecological techniques were used to examine the patterns of canopy recruitment in relation to disturbance history for two dominant, yet ecologically contrasting, tree species, Pinus strobus (white pine; disturbance dependent) and Tsuga canadensis (hemlock; late successional), in a 300-year-old primary forest. 2 Most tree recruitment in both species occurred between 1690 and 1810. All of the white pine, which dominated recruitment during the first 40 years due to more rapid height growth, recruited in this period. Low levels of hemlock recruitment continued until 1900. Most of the younger trees comprised several northern hardwood species. No trees were less than 50 years old and the forest was devoid of an understorey due to intense deer browsing. 3 Radial growth chronologies were determined for 27 cores across all species and age classes. These exhibited 1-11 major and/or moderate releases (indicative of disturbance) in most decades between 1730 and 1990. Peak releases were recorded in the 1950s when a series of severe windstorms impacted the site. Species recruitment patterns were related to earlier growth releases observed in the oldest cores. 4 White pine exhibited a degree of plasticity in initial radial growth (1-5 mm year-1) depending on the time of establishment, as well as the ability to survive through prolonged periods of depressed growth (< 0.5 mm year-1) followed by growth releases. Hemlock was less plastic in its initial growth rates but did have dramatic growth releases (up to 8.8 mm year-1) in several older trees. Thus, both species exhibited some unexpected dendroecological as well as successional attributes. 5 The future of this stand is uncertain due to the impacts of deer and insect outbreaks that plague the region, as well as fortuitous natural disturbances, e.g. wind and fire. Nonetheless, the dendroecological approach elucidated disturbance history, stand development and mechanisms of coexistence of two ecologically contrasting tree species, and should be used to further understanding of the complex ecology of other mixed-species forests and the successional role of various tree species.
All Science Journal Classification (ASJC) codes
- Ecology, Evolution, Behavior and Systematics
- Plant Science