Growth of black spruce seedlings planted in burned, logged, and undisturbed boreal mixedwood stands of southeastern Manitoba

Growth of black spruce seedling planted in burned, harvested, and undisturbed boreal mixedwood stands was studied in southeastern Manitoba. Although seedlings on each site were subjected to similar light competition (measured by % of full sunlight received at the middle crown of each crop seedling in 1998), mean annual growth of height, root collar diameter and aboveground biomass was different among the three sites, with burned > logged > undisturbed. During each of last seven years (1992 to 1998 except 1997), the burned site had greater annual height growth than the logged and undisturbed sites. Similarly, the logged site had greater height growth than the undisturbed site except 1997 and 1998. Relative competition intensity (calculated based on annual height growth from 1992 to 1998) fluctuated between 0.70 to 0.76 on the undisturbed site, increased from 0.48 to 0.73 on the logged site, and increased from 0.23 to 0.74 on the burned site. Relative competition intensity remained similar in the most recent three years (1996–1998) despite larger differences found in earlier years (1992–1995) between sites. A significant relationship was found between the relative competition intensity and % full sunlight on each site. Results from this case study suggested that, by affecting the development of competing vegetation, the type/intensity of past disturbances created different competition dynamics for black spruce seedlings planted on the burned, logged and undisturbed sites. Key words: interspecific competition, vegetation management, competition dynamics, plantation