[Effects of tree age and basal area on boreal forest tree mortality in Canada]

Taking the poplar (Populus spp.), jack pine (Pinus banksiana), and black spruce (Picea mariana) in northern Canada as test objects, a repeated investigation was conducted on the living and dead trees at 134 fixed sampling plots, and linear regression models were applied to study the effects of tree age, basal area, and stand type on the mortality of the three tree species. Generally, the tree mortality increased with increasing tree age and basal area. Poplar had a higher mortality in jack pine stand but a lower mortality in black spruce stand. In black spruce stand, tree age was the major factor affecting the mortality of jack pine, while in poplar stand, tree basal area was the important factor. In the three stands, tree age had significant effects on the mortality of black spruce. Species composition had significant effects on the mortality of the tree species, and the interactions between tree age, basal area, and stand type all had significant effects on the mortality of each tree species. The mortality of the same tree species in different stands differed significantly.