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Aspen Clones

Ranger Steve’s Nature NicheBy Ranger Steve Mueller

By Ranger Steve Mueller

Aspen tree clumps growing close to others change color at slightly different times. Within a single tree clump, the leaves often harmoniously change color at the same time. Weather and micro-climate might exert influence but so will the genetic makeup of the plants. 

Aspen trees are individuals much like each person is an individual with unique characteristics. You might look at an aspen tree and assume all trees are the same. That is like looking at a person and assuming all people are the same as every other individual. 

In the case of aspens, you might not be in complete error. A human family with identical twins has two individuals with the same genetic composition. Well almost. After egg fertilization, cells reproduce to develop the individual. In the process, some slight changes are likely to occur with gene inversion, duplication, or gene exchange on a DNA strand. These are minor but can bring about slight variation between the twins.

Aspens produce seeds but few survive. Growing conditions with proper moisture, temperature, and soil conditions must be present during seed dispersal. Mature seeds are abundant and easily blown in the wind. Most seeds land in locations that are not adequate to allow them to remain viable. Seeds sprout immediately and if conditions are not ideal they die. Most seeds become food for insects, fungi or some other organism.

Cloning from roots is the aspen tree’s primary means of reproduction. New stem shoots grow from long lateral roots and can rise quite a distance from the parent tree. They have the same genetic constitution as the original stem that sprouted from a seed. Characters like leaf shape, branching structure, disease resistance, pigment production, and timing for seasonal change are the same for each shoot in a clone. 

Environmental conditions like sun exposure, soil moisture, and nutrient supply affect various shoots of the same plant causing some variation as they respond to growing conditions. 

Two plants near each other that developed from different seeds will have unique characteristics like our family siblings. When they leaf out in the spring or change color in the fall, color intensity may vary. Fall colors might be different from one clump to another. This is evident when two clones are viewed during the spectacular fall color pageant. We can recognize identical clone individuals from neighboring clones at this time of year. 

Aspens are in the willow family and have male and female flowers on separate trees. All of the flowers in a clone will be of the same sex because members of the clone are genetically identical. 

When a seed establishes, it requires adequate moisture. Too much will facilitate fungal growth or drowning. Too little can cause desiccation. A surviving seedling will spread by cloning in a well-lighted habitat. New shoots are “sun loving” and cannot tolerate shade. An original stem can produce a mega-organism with hundreds of stems from root suckers having the same unique genetics. Stems in an identical clone will have slightly different nature niche adaptations from neighboring clones. 

Fire sweeping through and removing above ground stems creates sunny habitat for new stem sprouts. It is a fire adapted tree species that survives fire catastrophe and clear-cut logging. 

Aspens are thought to be among the largest individuals of living creatures. A particular stem is not as large as a redwood tree but its extensive number of stems from a single root creates more biomass than the redwood. 

Aspens might also be the oldest creatures on Earth attaining an age of more than 8,000 years. The tree stems do not normally live two centuries but the roots persist and continue to produce new stems. 

Natural history questions or topic suggestions can be directed to Ranger Steve (Mueller) at odybrook@chartermi.net – Ody Brook Nature Sanctuary, 13010 Northland Dr. Cedar Springs, MI 49319 or call 616-696-1753.

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