Relationships between patterns of stand growth dominance and tree competition mode for species of various shade tolerances

• A large sample plot network was used to relate growth dominance to stand attributes.
• For all species, growth dominance decreases with age and tree diameter diversity.
• Strong growth dominance was associated with size-asymmetric competition.
• Reverse growth dominance was related to more symmetrical competition between trees.
• Results can help improve tree selection rules for partial cutting.

The principal objective of the study aimed at establishing formal relationships between stand growth dominance and mode of inter-tree competition for stands dominated by different tree species. We selected permanent sample plots (PSP) that were established in eastern Canada and which were dominated by five tree species of differing degrees of shade tolerance: trembling aspen (Populus tremuloides Michx.), jack pine (Pinus banksiana Lamb.), white birch (Betula papyrifera Marsh.), black spruce (Picea mariana [Mill.] BSP), and balsam fir (Abies balsamea [L.] Mill.). The PSPs were used to calculate growth dominance coefficients (GD), together with the intercept (TCMint) and slope (TCMslp) of plot-level relationships between stem mass increment and stem mass, which were used to describe tree competition mode. GD decreased linearly with increasing stand age for all species, with highest GD values being observed in stands dominated by trembling aspen and lowest values being observed in stands dominated by shade-tolerant black spruce and balsam fir. Increasing stand diameter diversity was associated with a linear decrease in GD for all tree species. GD decreased with increasing TCMint, whereas it increased with increasing TCMslp. The linear relationships between GD and tree diameter diversity could estimate stand growth dominance without having to determine the recent growth of all trees. Also, the close relationship between GD and inter-tree competition mode suggests that this combined information is meaningful in helping to implement silvicultural treatments such as tree selection for partial cutting.