Aspen in North America is the most widely distributed tree Species and occurs in the heights frequency. (see shaded area on Attached map of North America).In the the boreal forest containing hard wood species near Drayton Valley where a portion of material for this study was sourced 90% of the hard wood is aspen with the balance being made up of various components of Populus Balsamifera and Betula Paperifera.
There are 31 different species in the genus populus (Dickman and Stuart 1983); however, there is still some debate, as Stelter (1996) estimates 40 species. Life history and ease at which natural hybrids occur in nature are compounding factors on the debate on species numbers. Species of populus are distributed primarily throughout Eurasia and North America (Zuffa 1975). (show cross wheel referenced to Zuffa 1975). Of all the species, there are three from section populus, formerly Leuce section, that are important for Tree Improvement work in Alberta due to cross-breeding potential. These trees, in addition to our native P. tremuloides Michx, are P. tremula L. and P. davidian Schneid. The significance of these trees is that they all come from northern climates: P. tremula from Europe, and P. davidiana from China and Korea.
Dickman (2001) makes reference to the fact that some researchers believe that all three of these species are descendants from one species that separated by continental drift. See figure at side for similarity in leaf morphology between three species.
