Quaking aspen (Populus tremuloides), a member of the willow (Salicaceae) family, is the most widespread deciduous tree in North America. Aspen range from Alaska in the North to Mexico in the South, from the Atlantic to the Pacific, and from sea level to an altitude of 12,100ft (3,700m). Among other willow, poplar, and shrub species, quaking aspen are commonly considered to have been among the first pioneers after the retreat of continental and alpine glaciers in the Pleistocene. While the species' geographic range is large, aspen stand location is limited to areas where annual precipitation exceeds 10 inches (400 millimeters) because of its high water needs. Interestingly, each stand is a set of clones: all of the trees are genetically identical. While aspens produce large amounts of viable seed, few seeds actually germinate and the primary means of reproduction for aspens in the west is via vegetative root suckering – genetically identical new shoots grow out of the roots of older plants. Some scientists estimate that significant sexual reproduction has not occurred in aspen for the last 10,000 years! While individual trees may only live 100-150 years, the clonal colony may exist for thousands. However, as the prolonged moist conditions necessary for successful seed growth are exceedingly rare in the Intermountain West, an aspen clone lost from the landscape will not generally regenerate from seed.
Did You Know?
Watch out for bombs! Before they cooled, volcanic bombs were hot globs of lava that were hurled from volcanoes along the Great Rift. They form a variety of interesting shapes described as "breadcrust", "spindle" and "ribbons" by geologists. More...