Distribution
The northern limit is determined by its intolerance of permafrost. It occurs across Canada in all provinces and territories, with the possible exception of Nunavut. In the United States, it can be found as far north as the southern slopes of the Brooks Range in Alaska, and it occurs at low elevations as far south as northern Nebraska and central Indiana. In the western United States, this tree rarely survives at elevations lower than 1,500 feet (460 m) due to the mild winters experienced below that elevation, and is generally found at 5,000–12,000 feet (1,500–3,700 m). It grows at high altitudes as far south as Guanajuato, Mexico
Shrub-like dwarf clones exist in marginal environments too cold and dry to be hospitable to full-size trees, for example at the species' upper elevation limits in the White Mountains.
Read more about this topic: Populus Tremuloides
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