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Species Found at Aspen Grove and Milk Canyon Ranch
With this expedition, I had "discovered" a second aspen island in the forest of piņon and juniper. The question of what conditions favor aspen growth persisted. I knew melting snow could make the aspen groves quite marshy. Could it be that aspens tolerate marshy periods but ponderosas and other conifers do not?  In the fall, aspen leaves turn a golden color. Gambel oaks grow from acorns, piņons grow from their nuts, but I didn't know how aspens handled reproduction. The cottonwoods in my backyard send sprouts up from their roots as a way of reproducing, so I thought aspens might send up shoots as well. I turned to my references and found that aspens, in fact, use both forms of reproduction. While aspens do release seeds, they prefer to send up shoots from the roots of a parent tree. Many aspens in one grove are clones of another aspen. Aspens that start as ramets, or suckers, from another tree's roots, will share characteristics with the "parent" tree. The aspen clone has the same sex, bark color, and branching habit, and breaks dormancy at the same time. Some aspens grow from seed, but this is rare. In The Sagebrush Ocean, photographer Stephen Trimble describes aspen groves in the arid West as island communities, remnants of the Pleistocene era. At the end of the last Ice Age, New Mexico had a cooler, wetter climate than it does now. Today, 10,000 years after the last Ice Age, aspen groves survive where conditions permit. The aspen groves I explored could be two of these islands. |
Many aspen groves, Trimble explains, consist of one clone in which all the aspens are genetically identical. Unlike aspen clones, "laboratory" clones of sheep and cats aren't true clones; they retain only 90 percent of their parents' DNA (Discover, January 2003, p. 31). One aspen may live only 60 years, but the trees from its suckers will continue to grow and reproduce. An aspen clone can grow for thousands of years, withstanding even fire. Is the single aspen trunk an individual, or do its multiple clones form one individual? On October 4, 2002, I visited the gully where I had seen aspens 12 days earlier. I measured its altitude at 7,100 feet. I counted three dozen aspens in the gully, all turning gold. I was surprised - very surprised - to find aspens at this lower elevation, but guessed that rainwater floods the gully. Extra water would encourage aspen growth. Aspens here prefer high elevations. The first aspen grove I explored has an altitude of 8,900 feet. But I also found aspens growing at 7,100 feet. Milk Ranch Canyon, at 7,500 feet, has no aspens. Higher elevations, with cooler temperatures, encourage aspen growth. Yet aspens survive in a moist microenvironment at a lower elevation. Are these 10,000-year-old aspens remnants of the last Ice Age? The soil at Milk Ranch Canyon is dry and sandy; at the first aspen grove, it is thick and dark. Canyon walls skirt around both aspen groves, and water runs into these canyons. Aspens here grow in valleys with a moist microclimate. Though elevation is a factor in aspen growth, water makes all the difference. In winter, aspens are bare. They look like giant icicles pointing to the sky. Spring brings pale green leaves that grow into the dark green of summer. Fall exhibits the aspens crowned with gold leaves. The aspens know intuitively what to do. They have practiced for years.  The aspen is self-pruning. Dead branches fall off and leave behind round black knots. I measure time in seasons and years. I remember that in the winter of 1998, we had lots of snow and went sledding every week. The following autumn, I picked piņons off trees and ate them raw. Each summer, I look forward to the July monsoons when I can smell rain in the air. From where I stand, I can't see the emerging patterns in my life. I only remember moments and short seasons. But aspens look back 10,000 years and see what has changed. I am dwarfed by tall trees with long memories. |
