The boreal forest stretches across Canada, Scandinavia, Russia and Alaska; in Canada the boreal forest represents 77% of the forested area and 35% of the total landbase (NRCAN). A large portion of the Canadian boreal forest is a mixture of aspen and white spruce, which has been shown to provide important habitat and increased biodiversity.
Differences are known to exist between the understory environment and vegetation of broadleaf, mixedwood and conifer stands, with mixedwoods being more similar to conifer stands. This suggests that the white spruce in the boreal mixedwoods is an important species which may act as an ecosystem engineer*. Although differences are known to exist, the timeline of changes between a 'broadleaf' understory to a 'mixedwood' understory are not known. How these understory changes spatially relate to the distribution of the white spruce is also not well known.
The objectives of this study are to characterize changes to the understory over time and in relation to white spruce distribution. To try to achieve this, mature aspen stands underplanted with white spruce are being studied. This allows the exact time of white spruce establishment to be known and controls to be established in non-underplanted areas of the same stands. Also, underplanting allows for set density and fairly consistent spacing of white spruce within a stand.
Differences are known to exist between the understory environment and vegetation of broadleaf, mixedwood and conifer stands, with mixedwoods being more similar to conifer stands. This suggests that the white spruce in the boreal mixedwoods is an important species which may act as an ecosystem engineer*. Although differences are known to exist, the timeline of changes between a 'broadleaf' understory to a 'mixedwood' understory are not known. How these understory changes spatially relate to the distribution of the white spruce is also not well known.
The objectives of this study are to characterize changes to the understory over time and in relation to white spruce distribution. To try to achieve this, mature aspen stands underplanted with white spruce are being studied. This allows the exact time of white spruce establishment to be known and controls to be established in non-underplanted areas of the same stands. Also, underplanting allows for set density and fairly consistent spacing of white spruce within a stand.
Fig. 1: Mature aspen stand in Lac La Biche, Alberta which was underplanted with white spruce in 1999 (photo taken in 2009).
Underplanting did not have an influence on the understory environment or vegetation community by 15 years after underplanting. This indicates the differences known to exist in the understory in terms of environment and vegetation between broadleaf and mixedwood stands develop sometime later than 15 years after white spruce establishment. Harvesting of the overstory aspen in underplanted stands is recommended 20-30 years after underplanting; there may be no influence to the ecosystem from underplanting before overstory harvesting occurs, after which harvesting effects would likely be the most influencing factor on the understory.
* "Ecosystem engineers are organisms that directly or indirectly modulate the availability of resources to other species, by causing physical state changes in biotic or abiotic materials. In so doing they modify, maintain and create habitats" (Jones et al. 1994).
Disclaimer: This website was created as part of a class exercise for RenR 690 by Erica Graham.